Using Geographic Information Systems (GIS) to Assess Lake Morphometry, Siltation-Induced Ecological Deterioration, and Land Use/ land cover practices on the Dry Bed of Chilua Lake, Tarai Region, India

Using Geographic Information Systems (GIS) to Assess Lake Morphometry, Siltation-Induced Ecological Deterioration, and Land Use/ land cover practices on the Dry Bed of Chilua Lake, Tarai Region, India | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Using Geographic Information Systems (GIS) to Assess Lake Morphometry, Siltation-Induced Ecological Deterioration, and Land Use/ land cover practices on the Dry Bed of Chilua Lake, Tarai Region, India Dr. Alka Singh, Prof. Vishawambhar Nath Sharma, Prof. Narendra Kumar Rana, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6523182/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Aquatic ecosystems regulate and play great ecological roles, for instance, provide habitats for flora and fauna, nutrient cycles, maintain stream flow, climatic control, and support livelihood security through fisheries, recreational activity etc. However, anthropogenic activities have dramatically deteriorated the aquatic ecosystem. Geospatial techniques are significant for the extraction of morphometric features of lake. An analysis of 97 years (from 1922 toposheets to Google Earth Images, 2019) of Chilua Lake in Tarai region , revealed deterioration scenario. The extent of Chilua Lake is reduced up 27.75% in 97 years from 1922 to 2019. As per the 500 m buffer analysis surrounds of lake Chilua, 1.3% built-up area increased around the lake within 15 years (from 2004 to 2019). For 6 to 8 months, the lake goes dry out and the water left behind in patches and engaged in various activities by the locals. Lake bed is covered by stream like storage (20%) and water is available during all seasons, water left in patches during dry season (15%), littoral plant coverage (45%), farming (11%), dry lake bed (10%), and built-up area (0.3%). Increasing built-up, farming on dry bed, dumping of solid waste and sewage entry have contributed directly pushed towards eutrophic status lake ecology at C1 (sewage entering sources) and C3 (agricultural practices) based on the BOD, BO, TP, NO 3 , SD, GPP, Chla, etc. This study investigates factors of lake deterioration and suggest the practices of Stewardship in the way of basin lake management techniques (BLMT) and Tripple-P model. Lake morphometric land use shallow lake trophic status index ecological deterioration stewardship Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 1. Introduction Lakes provide water for domestic use, drinking, agriculture, industry, and energy generation (Hyangya et al., 2021), and act as sinks for sediment and contaminants, thereby protecting downstream areas (Oskars et al., 2019). Most human communities surrounding lakes in developing countries are heavily dependent on lake biota (Jeppesen et al., 2017 ) and the natural processes of lakes for water, food, fibre, and livelihoods. However, as populations grow, lake resources come under increasing pressure (International Lake Environment Committee, 2005). In the age of climate change and rapid urbanisation, porous land surfaces such as bare soil and lake ponds are being transformed into impervious concrete surfaces. This transformation blocks the infiltration process, reducing groundwater recharge and increasing surface runoff (Albert et al., 2021). These changes are the by-products of deforestation and soil compaction caused by the covering of bare soil. Due to both natural and human causes, gradual siltation on the lake bottom has increased (Birk et al., 2020), limiting the lake’s capacity to store water year-round. Often, the dry lake bed is used for various natural and anthropogenic practices, which increases the potential for encroachment (Singh et al., 2024 ). Large amounts of silt deposition affect the morphometric properties of lakes. As a result, lakes gradually develop shallower depths, reduced extents, lower basin volumes (Meza et al., 2022), and an increasing shoreline development index (DL). Nutrients deposited along with silt are a consequence of human activities such as urbanization, agriculture, and industrialisation (Ansari et al., 2011 ; Downing et al., 1999 ). Continuous nutrient accumulation in surface water bodies accelerates algae and aquatic weed growth, leading to eutrophication (Alcocer, 2025; Pearl et al., 2001 ). Eutrophication results from the fertilization of aquatic ecosystems (Zou et al., 2020 ). Its most common feature is increased algal biomass, which often appears as layers of green algae on the water surface (Heino et al., 2021). This growth reduces water clarity (Li et al., 2018 ), interferes with oxygen mixing, and limits oxygen availability for aquatic organisms (Yang et al., 2016 ). Trophic status is a multidimensional concept that includes nutrient concentration, nutrient loading, productivity, floral and faunal diversity, and morphometric characteristics of water bodies (Schindler et al., 2008 ). Lakes are often affected by abrupt environmental changes caused by anthropogenic activities including industrial, agricultural, recreational, religious, and washing activities, along with solid and sewage waste disposal (Zhong et al., 2019 ). Remote sensing and Geographic Information Systems (GIS) techniques are useful in analyzing Google Earth images to study seasonal use of lake beds through classification, mapping, monitoring, and spatio-temporal assessment (Salman et al., 2021 ). The uncontrolled growth of the human population has placed severe pressure on lakes, rendering them non-potable, deteriorating water quality, impairing absorption capacity, disrupting aquatic biodiversity, and ultimately leading to the extinction of water bodies (Yang et al., 2023 ). The shrinking, pollution, and disappearance of these surface water bodies threaten sustainability, reduce water availability for human use, and endanger wildlife (Ramsankaran et al., 2023). Eventually, the extinction of these water bodies diminishes groundwater recharge (Ramchandran, 2001). Many water bodies—rivers, lakes, ponds, and canals—have lost their identity due to unregulated urbanization, lack of embankments, poor coordination among government agencies, and limited public participation in maintenance programs (Peker et al., 2019). In recent decades, water bodies in the Tarai region have suffered severe degradation in both water quality and watershed area. Consequently, communities around lakes experience acute problems like waterlogging and disease outbreaks during the rainy season. Lake shallowness has become a common issue due to surface runoff, stormwater runoff, agricultural runoff, flooding, and mismanagement of sewage systems in residential and remote regions (Jian et al., 2025). Aquatic weed overgrowth and human encroachment, such as constructing built-up areas on dry lake beds, further deteriorate such lake’s physical appearance and ecological health (Martin, 2014). Therefore, this study aims to examine the degradation in extent and water quality of Chilua Lake and the increasing built-up and encroachment activities in its surroundings. The major objectives of the study are: (1) To analyze changes in Chilua Lake’s morphometry from1922 to 2019 (2) To measure seasonal changes in the extent of the lake (3) To analyze land use practices on the dry bed of the lake (4) To examine the physicochemical status of lake water at various sites based on the level of anthropogenic interference, and (5) To discuss the key factors responsible for ecological deterioration in Chilua Lake. 2. Material and methods 2.1. Study Lake Chilua Lake (26°49'15'' to 26°56'50''; 83°20'9'' to 83°25'56'') is an oxbow lake of the Rapti River in the northeastern region (Singh 2020) of Uttar Pradesh, India (Fig. 1). It is fed by the Chilua Nadi (river) and extends approximately 19,000 meters through a narrow channel. Typically, the lake remains dry throughout the year due to insufficient embankments and shallowness of the basin, except during the monsoon season. The Chilua River, which traverses through the Chilua Lake, originates from the southern foothills of the Himalayas and ultimately discharges into the Rohini River. The genesis of Chilua Lake is associated with complex fluvial processes that have resulted in significant morphometric alterations over time. The Rohini River subsequently converges with the Rapti River, which in turn merges with the Ghaghra River, forming a part of the larger Gangetic River system. Chilua Lake functions as a natural reservoir, playing a crucial role in the temporary storage of excess monsoonal runoff, particularly during flood events in the Rohini and Rapti Rivers. During such events, surplus water from the Rohini River flows into the Chilua Nadi, contributing to the accumulation of water in the basin. This process causes annual bank erosion along the Chilua River, gradually reshaping the terrain and expanding the shallow basin, which eventually led to the formation and growth of Chilua Lake. Other significant streams in the area include Kuwano and Ami (Fig. 2). The lake is situated in the Himalayan foothills of Indian subcontinent at an elevation of 84 meters above mean sea level (Singh 2018, 2019). Chilua Lake receives approximately 1138.37 mm of rainfall during the rainy season, with a monthly average temperature of 22°C (approximately 11°C in winter and 31°C in summer), and an average relative humidity of 68%. These weather conditions clearly depict the humid Tarai region. In the Himalayan foothills, the Bhabar zone consists of coarse debris that allows water to percolate into the ground, whereas in the Tarai zone, finer soil causes groundwater to reappear at the surface. This results in high groundwater levels and frequent waterlogging problems in the region. The lake serves as a vital resource for local livelihoods, providing a rich habitat for diverse fish species and supplying water for agricultural activities, domestic consumption, and irrigation. 2.2. Acquisition of Lake Morphometric Parameters The morphometric characteristics of lentic ecosystems, including surface area, average depth, maximum depth, circumference, volume, maximum length, and maximum width are significant parameters for assessing the physical and ecological status of lakes (Wetzel, 1992; Kalff, 2002). The surface area of a lake defines its horizontal extent (Jorgensen, 2013). Average depth provides insights into the productivity and biological communities of a lake, as shallow lakes typically support more aquatic organisms than deeper ones. Circumference delineates the boundary between the lake and its surrounding environment and serves as an indicator of potential siltation from surface runoff. Lake volume, calculated as the product of average depth and surface area (Taube, 2000), indicates the lake's capacity to dilute incoming materials. Maximum length and width describe the lake's spatial dimensions, influencing wave dynamics and sediment resuspension (Wetzel, 1992). The maximum length is the maximum distance between any two distant points on the shoreline without intersecting a landmass. The larger the maximum length , the larger the waves, and the greater the potential for mixing and disruption of bottom sediments. Maximum width is measurement of the maximum wideness between two points on the shoreline (Wetzel 1992). The surface area change in Chilua Lake over a 97-year period (1922–2019) was determined by the comparing the digitized layers of lake area from Survey of India toposheets of the year 1922 on (toposheet no. 63 N on scale of 1: 250000) and 2004 (toposheet no. 63N/5, and 63N/6 on the scale of 1: 50000), and from Google Earth Pro (www.googleearth.com) for the year 2019 in QGIS 3.10 software using WGS 1984 datum and Universal Transverse Mercator (UTM) Projection. L ake extent, circumference, maximum length, and maximum width and the parameters such as lake volume, shoreline development and volume development were calculated using standard formulae within the QGIS Field Calculator. The depth of the lake was measured through an instrumental survey using a boat, a distance measuring tape, and a plumb-bob. Measurements were taken during both May (dry season) and September (wet season), and the final average depth was calculated using the following equation: Average depth of lake = (Max depth \(\:+\:\) Min depth ) /2…………………. Eq. 1 Where, Max depth : Maximum depth (m) and Min depth : Minimum depth (m). Depth measurements were further validated through responses from sixty local residents whose livelihoods depend on the lake for various purposes (Table 2.2). The volume of the lake (m³) was measured using Eq. 2 (Taube, 2000): Volume = Surface extent of lake water × Mean depth of lake ………. Eq. 2 The shoreline development index (D L ) reflects the degree of shoreline irregularity compared to a perfect circle (Hutchinson, 1957). Lakes with higher D L values are more likely to accumulate silt through surface runoff. It is calculated using lake extent and circumference as follows (Table 2.1 and 3): Table 1. Surface Extent of Chilua Lake from 1922 to 2019 Time Area (meter²) Change in area (meter²) Encroachment of extent (%) 1922 13801204.56 …… 2004 11683340.32 2117864.24 15.37 2019 9975504.46 1707835.86 11.31 Source: Computed by authors from the digitization of the lake in GIS environment Table 2.1 Shoreline Development (D L ) of Lake Chilua (2019) Name of lake Area in m2 L (circumference) 2πA D L = L/2 ѵπA Chilua 9975504.46 68387.78 11193.11798 6.109648887 Source: Computed by authors from the digitization of the lake in GIS environment Table 2.2 Volume Development (D L ) of Lake Chilua (2019) Name of lake Area in m2 Average depth in meter Maximum depth in meter Za (0.33Zm) A Dv = zA/(0.33Zm) A Chilua 9975504.46 2.7432 4.572 27332880.96 15669233.71 1.744366234 Table 2.3 Index of Basin Permanence (IBP) of Lake Chilua (2019) Name of lake SL (Shorelength) Average depth Area in m2 Volume (Av. depth*Area) IBP= V/SL Chilua 68387.78 2.7432 9975504.46 28489515.83 0.416587815 Source: Computed by authors from the digitization of the lake in GIS environment Table 3 Changes in the morphometric parameters of the lake over the years 1922–2019 Chilua lake Area in m2 Circumference in meter Max. length in meter Max. width in meter Shoreline Development (D L ) 1922 13801204.56 60302.51 6344.98 1072.39 4.580175013 Pre-monsoon in 2019 9975504.46 68387.78 6113.41 1043.12 6.109648887 Post- monsoon in 2019 18335403.02 85988.00 7289.32 2328.00 5.666276956 Source: Computed by authors from the digitization of the lake in GIS environment Where L is the circumference (m) and A is the lake area (m²) . Table 6. Utilization pattern of rural (Chilua) and urban (Ramgarh) lake (1980, 2004, 2019) Activities in Chilua Lake 1980 2004 2019 Fishing 65 83.33 100 Irrigation 30 53.33 91.66 Recreation 45 60 85 Religious Activities 50 55 66.67 Dumping Sites 0 31.66 65 Cattle bathing 60 75 85 Boating 28.33 53.33 70 Cereals cropping 66.67 91.67 100 Vegetable cropping 70 95 100 Washing 53.33 65 11.67 cooking and Drinking 30 8.33 0 Silt use 33.33 46.67 60 Vermiculture 0 16.67 23.33 Source: People's responses in percent during field survey (2019) Volume development (DV) is an indicator used to assess the deviation of a lake basin’s shape from a conical form to a flat, shallow basin. It is calculated using the maximum depth (Zmax) and the average depth (z) of the lake. For most lakes, DV > 1 indicates a deviation from the ideal conical shape, representing a more irregular or flattened basin (Hutchinson, 1957). DV values are typically higher in shallow lakes with flat bottoms (Table 2.1). The parameter is calculated using Eq. 4: DV = Za/(0.33×Zm) A………………………………………Eq 4 Where Dv = Volume development, Zm max = Maximum depth, Za = Average depth, A = Area of lake surface. The Index of Basin Permanence (IBP) is a morphometric parameter that reflects the influence of the littoral zone on the volume of the lake basin. Lakes with an IBP value less than 0.1 are typically dominated by rooted aquatic plants, indicating excessive shallowness, deep green water color, and high concentrations of Total Phosphorus (Kerekes, 1977). IBP values ranging from 0 to 1 indicate the lake’s proximity to senescence (Kerekes, 1977). The IBP (Table 2.3) is calculated using the volume of the lake and its shoreline development, as shown in Eq. 5: IBP = V / SL …………………………… Eq. 5 Where, V = Volume of the lake (m³) and SL = Shoreline development of the lake. 2.3. Land use/land cover changes The dried bed of Chilua Lake has been significantly impacted by agricultural expansion, vermi-culture, and residential encroachment, while the remaining parts of the lake are heavily infested with aquatic weeds, contributing to ecological degradation. To evaluate this deterioration, land use patterns within the dried lakebed were identified and mapped. The process is included identifying distinct land use/ land cover categories, classifying and digitizing them, and analysing their spatial distribution relative to the lake’s topography. Land use/Landcover classes were identified by field survey and the identified layer of various classes were digitized from Google Earth Pro (www.googleearth.com) for the year 2004, and 2019 in QGIS software. The results have been further validated using ground truthing, GPS coordinates, and enquiry from local community, providing critical insights into the accuracy and relevance of the findings. Land use change, particularly expansion of settlement was examined through buffer-based encroachment analysis using satellite imageries of 2004 and 2019 within a GIS environment. Data visualization and analysis were carried out using software tools including QGIS, Google Earth Pro, SigmaPlot, and MS Excel. Key indicators such as lake extent encroachment, habitat transformation, and the trophic status of the lake were mapped and assessed. 2.4. Lake Water Quality Assessment In Chilua Lake, three sites were selected for water sample collection, each chosen for representing different degrees of anthropogenic influence and assigned symbolic nomenclature (C1, C2, C3). Location 1, the Maheshra Bridge, located in the southwestern part of the lake, was designated as site C1. This site is significantly influenced by anthropogenic activities. It receives sewage from nearby urban areas, detergents from washing activities, and solid waste from religious offerings such as paper, flowers, cloth, and plastic, generated during marriage ceremonies and other socio-cultural rituals (Fig. 11). Location 2 or C2 is characterized by agricultural activities, including paddy, vegetable, and mustard farming (Fig. 11). In contrast, Location 3 or C3, on the other hand, shows minimal or no human interference (Fig. 1). However, due to the absence of embankments along the shoreline, silt through surface runoff freely enters into the lake. As a result, each location is substantially affected by nutrient pollutants and fine silt particles, which gradually increase the thickness of the underlying silt layer. This has led to a progressive shallowing of the lake, accompanied by the spread of littoral aquatic weeds. The Trophic State Index (TSI) was used to assess the level of eutrophication in the lake, based on Carlson’s Index (Carlson, 1977), which incorporates measurements of Secchi depth (SD), Total Phosphorus (TP), and Chlorophyll-a (Chl-a). Total Phosphorus was analyzed using the Olsen method. TSI (SD) = 10 (6- ln SD/ln 2)…………………………….….Eq. 6 TSI (Chl a) = 10 (6- 2.04-0.68 lnChl/ln 2)………………….Eq. 7 TSI(TP) = 10{6-ln(48/TP)/ln2}………………………….Eq. 8 The concentration of chemical parameters in the lake water was analyzed to assess the influx of nutrient pollutants and the increasing chlorophyll concentration in aquatic flora. The physio-chemical parameters were examined included TP, Nitrate (NO₃⁻), Biological Oxygen Demand (BOD), Dissolved Oxygen (DO), Chlorophyll-a (Chl a), Gross Primary Productivity (GPP), Chloride, Salinity, Total Dissolved Solids (TDS), Electrical Conductivity (EC), pH, SD, and Surface Water Temperature (Figs. 8 and 9). Water samples were collected in triplicates using pre-sterilized bottles between 07:30 and 10:30 a.m. at three sampling sites (Fig. 3). Dissolved oxygen was measured from sub-surface water samples using the modified Winkler method (APHA, 1998), while BOD was determined using an incubator. Phosphate-P was analyzed using the Olsen method, and Nitrate-N was determined using the brucine-sulphanilic acid method. GPP was assessed through the light and dark bottle method combined with the Winkler technique. Chlorophyll-a concentration was measured using standard spectrophotometric procedures (2004). EC, pH, salinity, and TDS were measured using a digital multi-parameter tester (model WA-2017SD). 3. Results The sequential development of human civilization has led to the deterioration of lake ecosystems across the planet. Silt deposition from surface runoff, agricultural runoff, and sewage sources has gradually reduced lake depth. As a result, many lakes are becoming increasingly shallow and are overrun by aquatic weeds such as water hyacinth, bulrush, and salvinia. This has caused distortions in morphometric parameters, degradation of water quality, and has pushed many lakes toward extinction (Adamczuk et al., 2020 ). The conversion of lakebeds for vegetable and cereal farming, solid waste dumping, and encroachment due to infrastructural development act as contributing factors to the extinction. 3.1 Changes in the morphometric parameters of the lake during 1922–2019 3.1.a Morphometric Analysis The surface area of Lake Chilua has shifted approximately 100 to 200 meters over a century, from 1922 to 2019. Generally, the course of the oxbow river or channel has also changed. Notably, there has been a remarkable alteration in the extent of surface water in Lake Chilua. This morphometric change is attributed to the Chilua Nadi, which historically converged with the Rohini River. Prolonged seasonal erosion has been observed in the Chilua Nadi during floods from the Rapti and Rohini Rivers, which has altered the course of the Chilua Nadi and shaped the oxbow configuration of the Chilua lentic ecosystem. Currently, the Chilua Nadi feeds into Lake Chilua, and the lake's outlet reconnecting with the Rohini River as it did in the past (Fig. 2 ). The unique morphology of this lake is maintained by the perennial presence of water, creating a rill-like channel that connects Lake Chilua throughout the year (Fig. 7 a and b). However, the current state of these water bodies supports its classification as a lake primarily due to the post-monsoon coverage of surface water. Consequently, the surface area of Lake Chilua is accurately assessed during the post-monsoon period, while it significantly diminishes during the pre-monsoon phase (Fig. 6 ). Surface water extent of lake Chilua in pre-monsoon is measured as 9975504.46 meter square while it is incraesed during rainy and calculated as 18335403.02 meter square. A huge difference observed from post-monsoon to pre-monsoon (Table 3 ). This fluctuation indicates a morphometric imbalance and excessive shallowness of the lake in the Tarai region. Such morphometric discrepancies lead to serious concerns regarding the lake's water quality. Several factors contribute to this issue in the shallow lake, particularly nutrient pollutants like total phosphorus (TP) and nitrate (NO3), which enter the lake from the unembanked shoreline via runoff, leading to silt accumulation. This results in rampant growth of aquatic weeds on the lake bed (Fig. 7 a), further degrading the lake's ecology as eutrophication levels increase (Karmakar, 2020 ). Therefore, The reducing values of IBP (0.42 which indicate less than 1) and the rise in eutrophication (60 to 80 TSI based on TP and SD) in Lake Chilua indicate ecological degradation (Figs. 8 and 9 , Table 2.3 ), characterized by morphometric alterations, which is a significant concern due to the lake's unique origin. This transformation occurred as the lotic ecosystem of Chilua Nadi transitioned into a lentic ecosystem, namely Chilua Lake, as a result of annual flooding from the nearby Rohini River. Consequently, the irregularities along the shoreline facilitated runoff, allowing nutrient pollutants to enter the lake. As a result, a substantial proliferation of aquatic weeds has been observed on the lake bed, accompanied by a eutrophic to hyper eutrophic status (Fig. 13 ). 3.1.b. Reduction in lake extent In 1922, the area of Chilua Lake was 13801204.56 m², and in 2019, the area has decreased to 9975504.46 m². There is a noticeable reduction in the extent of Chilua Lake from 1922 to 2019. The decrease suggests a change in the physical size of the lake over the observed period. The loss of area, the difference between the lake's extent in 1922 and 2019, is 3825700.10 m² (Table 1 and Fig. 4 ) which shows encroachment experienced by the lake bed. 15.37 Percent reduction of lake bed measured in 87 years and 11.31 percent reduction calculated in 15 years. It is clearly shown the anthropogenic pressure or nearby developed urban region on lake zone with the increasing of time period. The encroachment represents the portion of the lake that has undergone changes, potentially due to factors such as urbanization (Fig. 12 ), seasonal land-use/landcover changes (Fig. 7 a and b), or other environmental influences. Such alterations in the lake's extent can have environmental consequences, affecting ecosystems, aquatic life, biodiversity, water quality and the overall ecological balance of the lake. The reasons behind the reduction in lake area, factors such as human effluents and solid waste dumping (Fig. 5 a), climate change, land-use alterations, and local policies should be considered to better comprehend the dynamics influencing Chilua Lake. It might also be indicative of environmental changes, including issues such as sedimentation, urbanization, or climate-related impacts. 3.1.c. Current Scenario : The morphometric features of the lentic ecosystem (surface extent of lake water, average depth, maximum depth, circumference, volume, maximum length, and maximum width) are measured (Fig. 3 ) to find the deterioration (Wetzel 1992 and Kalff 2002 ). The extent of lake Chilua is 9975504.46 m². The average depth of the lake is 2.29 m which reflects that the lake is shallow. The circumference of the lake is 68387.78 m and the volume is 22804003.2 m3. The shoreline development is 6.12. Maximum length is 6113.41m and maximum width of the lake is 1043.12 m whereas fetch of the lake is 3578.26 m (Table 3 ). Lake with larger volume of water, low shoreline and volume development has more remarkable ability to dilute nutrient materials coming into the lake water. The maximum length and maximum with of this lake is also greater in the year of 1922 than in 2019 as well as greater value also calculated during post monsoon then pre monsoon (Table 3 ). Less than 1 shows more circular and lesser shoreline in distance. Hence, least potential to siltation through surface runoff while greater than 1 reflects larger circumference in in length and more irregular like elliptical, lunate shape of lake occurred. Shoreline development of lake Chilua was measured by 6.109. It clearly shows the shallowed lake basin due to larger circumference and huge distorted from a circular shape. Therefore lake bed has huge potential to enter surface runoff and silt deposition gradually filled the lake basin hence, a blue landscape change into grey and green landscape due to natural as well as anthropogenic actions. Moreover, D L of Chliua lake is calculated as 4.580175013 and 6.109648887 (pre-monsoon) in the year of 1922 and 2019 respectively while 5.666276956 measured in post monsoon in 2019. This kind measurement is clearly depicted in earlier time the shoreline distortion is lower than present and potential of siltation through runoff is also lower than present time. As well as increasing value of D L found during rainy season (Table 2.1 ). A positive relation is found between shoreline distortion and potential of siltation through runoff. Less than 1 shows the conical volumetric shape of lake basin while the greater than 1 reflects shallow lake. Volume development of lake Chilua was measured by 1.744 (Table 2.2 ). It clearly shows the shallowed lake basin due to distorted shoreline development. This situation of lake invited the huge amount of silt deposition hence, aquatic weeds covered the lake bed and in this way a aquatic habitats altered into terrestrial habitats due to natural and anthropogenic actions (Table 3 ). 3.2. Catchment, buffer zone and dry bed land use/land cover 3.2.a. Land uses on the dry bed of Chilua Lake The water is available for only few months in the entire lake bed. For 6 to 8 months, the lake goes dry out and the water left behind in patches. Thus, the dried patches are being engaged in various activities by the local people. Extent of lake bed is covered by (a) stream like storage (20%) in which water is available in all seasons, (b) water left in patches during dry season (15%), (c) littoral plant coverage (45%), (d) farming (11%), (e) dry lake bed (10%), (f) and built-up area (0.3%) (Fig. 7 a and b). This study explores levels of deterioration in the lake caused by either thick layer of silt deposition (both by natural run off and anthropogenic affluents) or encroachment by locals on lake bed. The lake, being shallow, holds water everywhere from shore to core for 2 to 3 months in rainy season and only 35 percent (15% area for water bodies and 20% for streams) water remains on lake bed for 8 to 9 months (except rainy season). 75 percent of the lake area is suffering from spread of littoral plants, anthropogenic encroachment for various activities (Fig. 7 a and b). The growing aquatic littoral floral (water hyacinth, water lily, etc. Figure 5 ) and siltation are preliminary factors which are gradually pushing the lake ecology towards extinction. 3.2.b. Spread out of siltation on Chilua Lake bed The Chilua Lake is largely influenced by gradual siltation due to natural surface runoff from surroundings, lack of proper embankment, and lack of dredging activity. In the lake basin, vertical siltation also occurs but focused on a major problem which is identified as the horizontal accumulation of silt and severely deteriorating the lake ecology. People have successfully encroached the shallow area of the lake by agricultural activities, residential encroachment, infrastructural development, etc. and as well as naturally covered through littoral plants on shallow lake beds (Yang et al., 2016 ). The lake zone is filled with water in the rainy season for two or three months but during the remaining month's lake dry out and thus used for crop and vegetable production, settlement encroachment, some part of land dries out, coverage of aquatic weeds and water in lake remained as patches like water bodies and rill like a channel from source to discharge point in the lake basin (Fig. 7 a and b). 3.3. Lake Water Quality Nutrients load in deposited silts into lake Chilua are consequence of human activities (Singh et al., 2020), such as increasing urbanization, agriculture, and industrialisation (Downing et al., 1999 ). Continuous accumulation of nutrients as underlying silt accelerates the production of aquatic weeds, leading to eutrophication (Carlson, 1977 and Zou et al., 2020 ) and analyzed by the BOD, BO, TP, NO 3 , SD, TDS, pH, EC, GPP, Chla, etc. (Figs. 8 and 9 ). The essential feature of eutrophication is increasing littoral biomass, which develops gradual siltation at the root of this prolific flora on surface water. It reduces water clarity and increase shallowness (Li et al., 2018 ), interrupts the oxygen availability for aquatic organisms (Yang et al., 2016 ). The ‘trophic’ is a multidimensional concept which includes nutrient concentration, productivity, floral and faunal diversity (Schindler et al., 2008 ). Lakes are often influenced by anthropogenic activities including industrial, agricultural, recreational, religious, washing, and etc. activities, solid and sewage waste disposal (Zhong et al., 2019 ). Therefore, the trophic status shown the level of eutrophication and ecological deterioration due to gradual siltation and growing of aquatic weeds on dry bed of lake extent. 3.3.1 Nitrogen and Total Phosphorus concentration Nitrogen and phosphorus are often identified as important limiting factors for algal biomass. The excess input of nutrient pollutants results in the proliferation of planktonic alga and which disrupts the entire aquatic environment. Orthophosphate is one of the forms of P that autotrophs can be assimilate. Excessive production of autotrophs, especially algae and cyanobacteria can lead to eutrophication which pose very serious effect on overall water quality including trophic relationships. The study showed that the Total Phosphorus and Nitrate were recorded highly during summer due to low water level remained after the evaporation and hence high toxicity concentration appeared. Whereas moderate concentration found during winter due low evaporation and huge water remained from rainfall, and low concentration measured during rainy due to dilute the toxicity with huge amount of rainy water in the Chilua Lake. This could be occurred due to anthropogenic influences (sewage source from the city area, washing activity and ceremonies like religious offerings) at C1. The concentration of nutrients pollutants load (TP and NO 3 in mg/L) moderately found at C2 site due to agricultural activity on lake during dry season and along the lake shore. But low concentration of nutrient pollutants (TP and NO 3 ) was recorded at C3 site due to lack of any specific kind of anthropogenic interferences (Fig. 8 ). In winter season, the level of Total Phosphorus a bit moderate relatively less amount of these components entering to the lake. Also, the algal biomass starts to develop algal blooms and algal mats as a layer on the surface of water. In summer season the orthophosphate level declined further due to still excessive use by primary producers together. The concentrations of TP in mg/L were; 1.10 (winter), 1.47 (summer), 0.99 (rainy) at site C1; 0.015 (winter), 0.045 (summer), 0.009 (rainy) at site C3; 0.93 (winter), 1.24 (summer), 0.87 (rainy) at site C2; respectively (Fig. 7 and Table 4 ). Nitrate is also following the same trend of Dissolve reactive Phosphorus. In the similar way, the values of Nitrate were 7.37 (winter), 8.92 (summer), 7.09 (rainy) at site C1; 6.33 (winter), 7.89 (summer), 6.12 (rainy) at site C2; 1.78 (winter), 2.01 (summer), 1.63 (rainy) at site C3; respectively in rural surrounding Lake Chilua (Fig. 8 and Table 4 ). Tropical lake has been severely influenced by anthropogenic activities which degrade the water quality and also the aesthetic values (Wade, 1999 ) at site C1 due to receive large quantity of untreated domestic effluents from city region, detergent from washing activity, residue from ceremonies like religious offerings along the lake shore. Whereas agricultural (cereal and vegetable crops) activity done on dry bed of lake extent during summer and winter (Fig. 11 ) at site C2. Whereas mesotrophic level recorded at C3 due to less anthropogenic activity (Fig. 8 ). 3.3.2 Biological Oxygen Demand and Dissolved Oxygen level The BOD refers to demand of oxygen for decomposing the organic matter waste through biologically (bacteria) active of living organisms in aquatic ecosystems. In this study BOD level was high in summer due presence of massive algal bloom in the lake. The oxygen is used in decomposition of nutrient pollutant. During rainy season the BOD level remains moderate due to rainfall mediated dilution of organic waste. In winter season the BOD remains low because biodegradation of waste material through bacteria occurs on spatial scale. The concentration of BOD was recorded in mg/L as 11.92 (winter), 12.89 (summer), 12.06 (rainy) at site C1; 4.98 (winter), 5.96 (summer), 5.24 (rainy) at site C3; 10.28 (winter), 12.07 (summer), 11.53 (rainy) at site C2 respectively (Fig. 8 and Table 6). As expected, the DO showed a trend opposite to BOD. It was found to be 5.88 (winter), 5.0 (summer) and 5.34 (rainy) at site C1; 7.98 (winter), 6.33 (summer), 7.14 (rainy) at site C3; 6.09 (winter), 5.09 (summer) and 5.41 (rainy) in mg/L at site C2 respectively in lake Chilua (Fig. 8 and Table 4.1). The dissolved oxygen (DO) in water ensures survival of living organism in aquatic ecosystem. It is needed for respiration of fish and other organism in aquatic system. The D.O. enters in freshwater after diffusion from atmosphere and by-product of photosynthesis by algae and other plants. However, epiliminetic waters and shallow lake progressively equilibrate with the atmospheric oxygen concentration. The Lake Chilua is deep lake but low IBP promote the shallow lake beds with huge coverage of aquatic weeds. In this lake, DO was high in winter due to high oxygen holding capacity of water and also rate of decomposing waste. The DO was moderate in rainy season due to dilution effect and high in late summer due to presence of algal mat in lake water. In summer to over-saturation of algal bloom and low oxygen holding capacity of water reduces the DO level and cause problem to surviving biota and may result in fish kill (Singh 2020 ). The DO inversely relates BOD, and accordingly the former is high in winter and moderate in rainy and less in summer season (Fig. 8 ). 3.3.3 Chlorophyll and Gross Primary Production The amount of chlorophyll in urban lake was high in winter due to conducive condition including nutrients whereas in rainy season chlorophyll declined due to dilution effect from rainy water. But it is recorded low concentration in summer due to decomposition of living organism by excess temperature. The concentration of chlorophyll is low in sewage water due to high turbidity coupled less penetration of light. Away from these polluted sites and due to presence of high amount of nutrient the algal bloom grows and proliferate resulting eutrophication condition seen in the lake. Very far away from sewage site and less anthropogenic influences such as the chlorophyll was found low at site C2. The declining nutrient concentration caused reduction in chlorophyll biomass (up to 41.4%) and primary productivity (up to 32.2%) reflecting a reversal of eutrophic status towards oligotrophic. The GPP showed similar trend as Chl a with rapidly declining trend in lake water. The values of Chlorophyll in mg/L were 19.11 (winter), 10.92 (summer) and 4.09 (rainy) at site C1; 6.89 (winter), 4.01 (summer) and 2.1 (rainy) at site C3; 14.79 (winter), 6.73 (summer) and 4.09 (rainy) at site C2 respectively (Fig. 8 and Table 4.1). The GPP followed a similar cause effect relationship and the trends were similar to chlorophyll concentration. In this way, 6.12, 4.43 and 3.9 at site C1; 1.1, 1.02 and 0.9 at C3; 5.48, 3.9 and 3.5 in mg/L at C2 in winter, summer and rainy respectively (Fig. 8 and Table 4.1). Secchi depth was high in rainy season and low in summer and moderate in winter. It was recoded as 0.66 (winter), 0.73 (summer) and 0.42 (rainy) at site C1; 1.02 (winter), 1.19 (summer), 0.81 (rainy) at site C3; 0.57 (winter), 0.65 (summer), 0.3 cm (rainy) at site C2 in Chiua lake (Fig. 8 and Table 4.1). The increasing concentration of TDS and Chlorophyll represent the decreasing concentration of Secchi depth because it shows the presence of anthropogenic influences (domestic sludge, detergent, residue from ceremonies like religious offerings, etc.). 3.3.4 Salinity and Chloride : The range of salinity which determines the range of chloride in aquatic system is also affected by domestic and industrial effluents. In the Chilua Lake, moderate concentration of chloride as well as salinity could be linked to sewage from city region. Temporally, it was high in rainy due to catchment inflow from surroundings into lake through rainy water. Whereas in summer, chloride and salinity amount was high due to less dilution effect, but it is least recorded in winter due to moderate level of water availability and lack of catchment inflow into lake. Chloride concentration followed a declining trend from sewage water towards remote location (lesser influence of human activity). It was high to low in rainy, summer, and then in winter. The concentration of Chloride in mg/L was found to be 56.81 (winter), 67.43 (summer) and 63.38 (rainy) at site C1; 48.4 (winter), 53.89 (summer) and 50.27 (rainy) at site C3; 51.41 (winter), 58.29 (summer) and 55.21 (rainy) at site C2 respectively (Fig. 9 and Table 4.2). As expected, the Salinity showed a similar trend to Chloride. It was found to be 196, 200, and 198 NTU at site C1; 165, 162, 169 NTU at site C3; 186, 197 and 181 NTU at site C2 in winter, summer, and rainy respectively (Fig. 9 and Table 4.2). 3.3.5 Total Dissolved Solids, Electrical conductivity, pH, and Surface Temperature The TDS, electrical conductivity, pH, and surface water temperature all remain high in summer followed by rainy and winter respectively (Fig. 9 and Table 4.2). The TDS recorded low at dredging site C1 (321, 426 and 400). Towards north-east, the value increased (109, 126 and 118 at C3; 344, 443 and 423 mg/L at site C2 in winter, summer and rainy respectively. Large amount of suspended particulate matter enters freely into the lake through catchment inflow during rainy season and it is severely affecting the lake beds due to lack of any embankment which prevent the surface runoff from surroundings. Electrical conductivity also followed a similar trend. The values were detected in µs about 506 (winter), 525 (summer) and 516 (rainy); at site C1; 303 (winter), 416 (summer), and 400 (rainy) at site C3; 428, 445 and 433 µs; at site C2 respectively (Fig. 9 and Table 4.2). Therefore, the residue from anthropogenic activity sewage effluents came through seasonal runoff into the lake catchment and increase the concentration of Electrical Conductivity. It is reduced towards the lesser influenced sites by human activity. The pH values again match with these above trends. The pH did appear at 7.21 (winter), 7.25 (summer) and 7.2 (rainy) at site C1; 7.11 (winter), 7.15 (summer), 7.09 (rainy) at site C3; 7.16 (winter), 7.21 (summer), and 7.17 (rainy) at site C2 respectively (Fig. 9 and Table 4.2). This was probably due to the presence of a variety of nutrient pollutants by agricultural runoff, surface runoff, and one sewage runoff from city region. The surface water temperature is recorded in ℃ with very little variation among site and due to sample collection from each site at very small-time interval. Low to high temperature recorded followed the atmospheric temperature trend. Surface temperature was recorded 19.6, 27.7 and 24.3 at site C1; 20.5, 28.6 and 25.7 at site C2; 20.6, 28.9 and 25.9 ℃ at site C3 in winter, summer and rainy season respectively (Fig. 9 ). 3.4. Responsible factors of siltation in Chilua Lake The lake water also mixed with sewage and municipal solid wastes. In the lake bed, some places suffer from high concentration of nutrient pollutants and silts due to dumping of city’s solid waste and agricultural activities. The responsible factors of spread out of siltation in the Chilua Lake bed, observed from GIS analysis and field investigation are: (i) Natural and anthropogenic runoff : The rural lake is fed by surface runoff, surplus water of Rohini river during flood (Fig. 2 ), agricultural runoff (Singh 2020 ) and also by the anthropogenic effluents from one sewage entering point (Fig. 10 ). Dumping the sewage waste into lake is easiest option available to local city dwellers and authorities because the residential soak pits are less successful due to the high ground water level in Tarai region. One sewage source enters near sample site C1 and freely into lake and carried the city area wastes. (ii) Lack of concrete embankment : Water stored in shallow lake in all seasons largely depend on the embankment. Chilua Lake has become gradually shallow, and water remains only in patches and rill like channels due to lack of any kind of kachha or pacca embankment which holds the water storage and also prevents lake shore from erosion and checks the entry of the amount of eroded soil (Figs. 5 and 11 ) in lake bottom as silt (Singh 2022 ). (iii) Encroachment : The extent of Chilua Lake is reduced up 27.75% in 97 years from 1922 to 2019. Reduction in lake shore is the result of lack of proper boundary demarcation or proper construction of embankment and gradual silt deposition. Hence, the shallow lake bed is filled and covered by aquatic weed (Fig. 7 and Table 1 ). (iv) Circumference of the lake : circumference is the way to measure the lake's openness (Lakewatch 2001 ). A larger circumference has the larger potential for allowing entry of eroded material or fine silt into the lake zone due to large boundary. Lake Chilua has large circumference (68387.78 m) and poses huge potential of silts deposition through surface runoff due to highly irregular distorted shore (Fig. 3 , Table 2.1 and 3 ). (v) Land uses/Landcover changes in surrounds : Lakes are normally healthy, and fruitful for all aquatic organism and many livelihoods for people like agriculture, vegetable cropping, irrigation, cattle bathing, ceremonies like religious offerings, vermiculture and use as drinking water etc. offered which have been catering to the anthropogenic, ecological, and environmental needs in the surrounding. Moreover, some potential uses of lakes are also prominent like forest surrounding the lake, development of aquatic biota, sink for temperature control, polluted water and soil and healthy aquifer. However, as time goes on from 1980 to 2019 and human activity increases, these usefulness changes. In 1980, fishing in Chilua Lake was moderate, but as the population density around the lake expanded, fishing continued to be appropriate untill 2019, but it was not commercially viable due to inadequate government support. There is plenty of space for irrigation around Chilua Lake, but it is primarily used locally due to its mild irrigation. The lake bed region is used to cultivate a range of crops in the winter, such as wheat, mustard, and various vegetables like cauliflower, potatoes, peas, carrots, and more. A total of 60 respondents (100%) confirmed vegetable cropping and agricultural production. They produce for both personal and business purposes. Due to a lack of private or governmental concern about the park, hotel, restaurant, etc., recreational opportunities were extremely limited and utilized exclusively by locals. Locals and others in the vicinity used the lake extensively for ceremonies purpose like religious offerings including Chhat puja, marriage and other social rituals, idol immersion (Fig. 11 ) during numerous festivals, etc. (Singh 2020 ). Because the livelihood and way of life of the surrounding people depended on natural resources. Dumping sites area on the lake bed increased with the increasing of population number where municipal solid wastes largely dumped from city's outskirts. As a result, 65 percent dumping activity increased within 39 years. Forty-two people (70%) agreed that there was a lot of cattle bathing on the lake area. Boats were used in Chilua Lake for fishing, gathering fodder crops, and other purposes. The use of washing in Chilua Lake was decrease by local due to increasing shallowness. Brick chimneys set up along the lake and use the sediment deposits of the lake bed. Vermiculture, such as earthworms, thrives and is used by the locals as biofertilizer on agricultural land from the early years (Table 6). (vi) Increasing built-up activities around the lake : In the buffer of 500 m, built-up activities are prohibited as per the National Green Tribunal’s guidelines (Kasture 2022 ). Despite this fact, built-up activities including residential, commercial, administrative buildings and other infrastructural development are increasing in the lake zone. These encroachments depict congestion, and pressure of human interference on the lake due to uncontrolled and unplanned development processes. In 500-meter buffer (Fig. 12 ) Chilua Lake is covered by a total area of 9975504.46 m² and 1.31 per cent area is encroached by built-up activities. (vii) Lack of Monitoring and management of lake : The safe guard measures of stewardship such as development of embankment, harvesting of aquatic weeds (Hansson et al., 2018), dredging out of silts, and afforestation rejuvenate the lake from its shallow character. Although some steps of stewardship are initiated in Chilua Lake, significant remedial actions had not been taken yet in any parts of lake zone. Therefore, lake is neglected and keeps on suffering from excess shallowness and littoral plant coverage (Singh 2020 and 2024). (viii) Increasing eutrophication in lake water : Continuous nutrient buildup as underlying silt speeds up aquatic weed growth, causing eutrophication, which is measured by the TP, SD, Chl a, etc. (Fig. 13 ). Because of the shallow epilimnion lake's high turbidity, TSI values ranging from 60 to 84 were measured based on Secchi depth. Due to the intake of agricultural fertilizer through free surface runoff, the TSI ranged from 40 to 80 based on TP. Because of the flowery cover on the lake's bottom floor, 30 to 60 TSI were observed based on Chl a (Fig. 13 ). Anthropogenic activities (agricultural, recreational, religious, washing, etc.) that increase nutrient content, productivity, and floral and faunal diversity in lake water (Schindler et al., 2008 ). Because of the slow siltation and the growth of aquatic weeds on the dry bed of the lake extent, the trophic status thus indicated the degree of eutrophication and ecological degradation. 4. Discussion 4.1. lake Stewardship and potential uses In recent years, there had been a growing concern over the increasing nutrient pollutant loads and eutrophication in freshwater lakes (Beklioglu 1999 ; Pandey and Pandey 2013 ). These changes lead to continuously decline in the amenity, aesthetic enjoyment, recreational value, and quality of freshwater lakes (Sondergaard et al., 2000). Urban rapid development not only increased the rates of sewage discharge and sediment delivery but also encroached the riparian corridors. Surrounding the lake and streamside, mini forest is being developed for the stream stabilization, protection of banks and bed from erosion (Booth et al., 1996). A number of approaches have been examined and proposed all over the world to control eutrophication. Widely accepted method focuses on controlling external nutrients input to control eutrophication (Jeppesen et al., 1999). This approach has been proved effective mostly for deep lakes although less effective for shallow lakes (Beklioglu 1999 ). In recent time, sediment dredging has been used effective approach and tool to bring down the internal flushing of surface to bottom nutrients in shallow lakes (Sondergaard et al., 2000; Pandey and Verma 2005). Sediment dredging removes accumulated nutrients specially phosphate from the bottom layer sediment and supports internal flushing (Jeppesen et al., 1999; Sondergaard et al., 2001) and progressive reversal of the lake health from eutrophic stage to Oligotrophic stage. Sewage treatment plants add phosphorus into surface water bodies (APHA 1985 and 1998). Normally, an adult excretes (getting rid of solid waste material from human body) 1.3–1.5 gm of phosphorus every day. Primary treatment removes 10% phosphorus only from the sewage waste; secondary treatment removes 30% only and remaining is discharged freely into water body (Harper 1992 ; Rhodes 2013 ). Thus, tertiary treatment is essentially required to remove phosphorus from the water. In total, immediate actions are required to conserve and restore the lake ecosystem and its aquatic resources. Protecting existing grassed area and trees in the catchment prevents erosion. Proper treatment of domestic wastes and safe application of fertilizers reduce nutrient’s entry into the lake. Other techniques of stewardship are followings: 4.2 Basin lake management techniques (BLMT) include: Basin lake management techniques (BLMT) involves (1) Removing excess sediments in lakes which can help eliminate nutrients and aquatic weed growth, deepen area for recreational uses and remove toxic or other contaminated substances (2) Adding aluminium sulphates to lakes which can help to control algae by making phosphorus and the nutrients that drives algal blooms, unavailable for use (3) Stabilizing lake shorelines can decrease sediment’s load and turbid conditions in lakes (4) Mechanical removal of excessive grown aquatic plant which increases areas available for recreation, navigation, irrigation and helps removing the source of nutrients released by decaying plants, which can in turn, decrease algal blooms (5) Adding oxygen to a lake through aeration devices which can prevent fish kills, create conditions unfavourable for algal blooms and improve the taste and colour of water (Bronmark 2018 ). Specific research for such individual lake for further protection and management of the lakes are needed. In this way, the immediate effect on integrated lake basin management will be seen after implement of Triple-‘P’ model. Hence, the Chilua Lake will be comes out from the category of shallow deteriorated eutrophic lake. However, some negative impact can develop after implementation of BLMT for specific lake. Such as, it might be promoting lake beautification as well as visitors’ attraction and then noticed some solid wastes surrounds lake (Sheergojri et al., 2023 ). 4.3 Triple- ‘p’ model For restoring of lakes in the study area, ‘Triple- P’ model prevention, protection and promotion can be used for holistic stewardship. 27 indicators of this model (Ban on solid waste dump, detergent use, idol immersion, built up activity surroundings 50 m, make proper embankment, promote afforestation are formulated to steward the lake in the study area (Table 5). Acknowledging the importance of lakes for the living organism, as well as for maintaining the ecological balance for environmental sustainability, the deterioration of lentic ecosystems is matter of concern (Hanazato 2001) due to population pressure and unplanned economic, developmental, and other human activities. The study finds out that the Chilua Lake is largely affected by intense agricultural activities, built-up land encroachment, solid waste dumping, and sewage entry in lake catchment. The study presents a comprehensive understanding of the degradation of Chilua Lake's ecosystem, emphasizing the multifaceted factors contributing to its current status. It delves into various aspects such as morphometric features, reduction in lake area , land uses on the dry bed, siltation, responsible factors of siltation, and stewardship and potential uses of the lake to understand the complexity of natural processes and human activities shaping the current state of the lake. 5. Conclusion The study identifies natural and anthropogenic runoff, lack of embankments, encroachment of surface extent, large lake circumference, land uses of lake bed, trophic status of lake water and lack of monitoring and management as key factors contributing to siltation in Chilua Lake. The accumulation of silt leads to the shallowing of the lake bed and the proliferation of aquatic weeds, pushing the lake ecology towards extinction based on less than 1 IBP and more than 1 DV. The morphometric features of the lake are analysed, revealing a decrease in depth and volume over time. These measurements indicate a shallower body of water, which is more vulnerable to environmental stress. Additionally, the reduction in lake area over the 97 years is observed, with urbanization, land-use changes, and lack of management strategies being identified as key drivers. This reduction has significant implications for biodiversity, eutrophic status of water quality, and overall ecological balance of the Chilua Lake. The utilization of the dry bed of Chilua Lake for various activities such as farming, settlements, and infrastructure development exacerbates the degradation of the lake ecosystem, further threatening its sustainability. Siltation emerges as a major issue affecting the lake. This study underscores the urgent need for immediate actions to conserve and restore the lake ecosystem. Recommendations include protecting catchment area , treating domestic wastes, dredging excess sediments, stabilizing shorelines through embankment, and implementing lake management techniques to control aquatic weeds and improve water quality. Overall, the study provides valuable insights into the challenges facing Chilua Lake and other freshwater ecosystems. It advocates the implementation of holistic management approach. By implementing Tripple-P model, basin lake management techniques (BLMT) and engaging local communities, policymaking can be done to work towards preserving and restoring these vital natural resources for future generations. 6. Research Limitations A key limitation of this study is the unavailability of historical data for the year 1922, which significantly constrained the analysis of Chilua Lake’s morphometric characteristics during that period. Since direct observation or measurement is not feasible for historical conditions, it was not possible to obtain primary data for 1922. Furthermore, no secondary sources were found to contain essential morphometric information such as average depth or volume of the lake. Consequently, critical parameters such as DV, IBP, and average depth could not be calculated for the year 1922. Additionally, the unavailability of boats and poor navigability due to the shallowness of bed of the lake made it impossible to measure depth and the thickness of silt at multiple locations except the three locations during this research study. Declarations Acknowledgment The datasets analyzed here were combined with funding from the University Grant Commission, India and laboratory experimentation done in Department of Botany, Banaras Hindu University. We are thankful to all the organizations and people involved in this research work and data collection. Disclosure statement No potential conflict of interest was reported by the authors. Clinical trial number : not applicable in this manuscript. Ethics, Consent to Participate, and Consent to Publish declarations: not applicable in this manuscript. Funding This work was supported by the University Grants Commission Data availability statement Data will be made available if asked and required. References Adamczuk M, Pawlik-Skowrońska B, & Solis M (2020) Do anthropogenic hydrological alterations in shallow lakes affect the dynamics of plankton? Ecological Indicators, 114, 106312. Anonymous (2001) State of Environment Report, India Chapter, United Nations Environment Programme Publications. Ansari AA, Gill SS, & Khan FA (2011) Eutrophication: threat to aquatic ecosystems. Eutrophication: causes, consequences and control, 143-170, DOI 10.1007/978-90-481-9625-8 APHA (1985) Standard Methods for the Examination of Water and Wastewater. — American Public Health Association. Washington DC. 268 pp. APHA: Standard methods for the examination of water and wastewater, 20th edition, APHA, AWWA, WEF (1998). Beklioglu M (1999) A review on the control of eutrophication in deep and shallow lakes, Turkish Journal of Zoology, (23), pp. 327-336. Booth DB, & Jackson CR (1997) Urbanization of aquatic systems: degradation thresholds, stormwater detection, and the limits of mitigation 1. JAWRA Journal of the American Water Resources Association, 33(5), 1077-1090. Bronmark C, Hansson LA (2018) The biology of lakes and ponds, 3rd edn. Oxford University Press, Oxford Carlson RE, (1977) A trophic state index for lakes, Limnology, and oceanography, 22(2), pp. 361-369. Cunha DGF, do Carmo Calijuri M, & Lamparelli MC (2013) A trophic state index for tropical/subtropical reservoirs (TSItsr). Ecological Engineering, 60, 126-134. Downing J A, McClain M, Twilley R, Melack J M, Elser J, Rabalais N N, & Howarth RW (1999) The impact of accelerating land-use change on the N-cycle of tropical aquatic ecosystems: current conditions and projected changes. New Perspectives on Nitrogen Cycling in the Temperate and Tropical Americas: Report of the International SCOPE Nitrogen Project, 109-148. Galvez-Cloutier R, and Sanchez M (2007) Trophic status evaluation for 154 lakes in Quebec, Canada: monitoring and recommendations, The Water Quality Research Journal of Canada, 42(4), pp. 252-268. Hanazato T, Arakawa T, Sakuma M, Chang K-H, Okino T (2001) Zooplankton community in Lake Suwa: Community structure and its role in the ecosystem (in Japanese). Jpn J Limnol 62:151–167 Harper DM (1992) Eutrophication of freshwaters (p. 327). London: Chapman & Hall. Hoyer MV, Frazer TK, Notestein SK, Canfield J, and Daniel E (2002) Nutrient, chlorophyll, and water clarity relationships in Florida’s nearshore coastal waters with comparisons to freshwater lakes, Canadian Journal of Fisheries and Aquatic Sciences, (59), pp. 1024–1031. Hutchinson GE (1957) A treatise on limnology: Geography, physics and Chemistry, Volume 1, Wiley, New York, Chapman & Hall, London. pp. 108-114. Jeppesen E, Søndergaard M, & Liu Z (2017) Lake restoration and management in a climate change perspective: an introduction. Water, 9(2), 122. Jorgensen S, Tundisi JG, and Tundisi TM (2013) Handbook of Inland aquatic Ecosystem Management, Applied ecology and environment management, Taylor and Francis group, ISBN- 13: 978-1-4398-4526-4, pp. 1-421. Kalff J (2002) Limnology. Inland water Ecosystem, Mc Gill University, prentice Hall, pp. 1- 536. Karmakar, S., & Musthafa, O. M. (2020). Lakes and reservoirs: Pollution. In Managing Water Resources and Hydrological Systems (pp. 65-80). CRC Press. Kasture, R. (2022). Critical study of role and functions of national green tribunal in protection of environment in India. Journal Homepage: http://ijmr. net. in, 10(2). Lakewatch F (2001) A Beginner’s guide to water management-Lake Morphometry. Information Circular, 104. Lambin EF, Turner BL II, Geist HJ, Agbola S, Angelsen A, Bruce JW, Coomes O, Dirzo R, Fischer G, Folke C, George PS, Homewood K, Imbernon J, Leemans R, Li X, Moran EF, Mortimore M, Ramakrishnan PS, Richards JF, Skånes H, Steffen W, Stone GD, Svedin U, Veldkamp T, Vogel C, Xu J (2001) The causes of land-use and land-cover change – Moving beyond the myths Global Environmental Change, Human and Policy Dimensions, Vol. 11 (4), pp. 261-269. Laudise JE, Laudise RA, Graedel JE, and Barns RL (1994) Water quality analysis of Twin Lakes PA, 1965-1993, A unique database, Journal of Pennsylvania Academy of Science, 68(2), 67-76 (1994). Li J, Hansson LA, & Persson KM (2018) Nutrient control to prevent the occurrence of cyanobacterial blooms in a eutrophic lake in Southern Sweden, used for drinking water supply. Water, 10(7), 919. Liu Y, Chen W, Li D, Shen Y, Li G, and Liu Y (2006) First report of aphantoxins in China—waterblooms of toxigenic aphanizomenon flos-aquae in Lake Dianchi, Ecotoxicology and Environmental Safety, Elsevier, (65), pp. 84–92. Ohle W (1937) Kolloid Gele als Nahrstoff regu- latoren der Gewasser, Naturwissenschaf ten, 29, pp. 471-474. Purmalis O, Kļaviņš L, & Arbidans L (2019) Ecological quality of freshwater lakes and their management applications in urban territory. Proceedings of the Research for Rural Development, 1, 103-110. Paerl HW, Xu H, Hall NS, Rossignol KL, Joyner AR, Zhu G, and Qin B (2015) Nutrient limitation dynamics examined on a multi-annual scale in Lake Taihu, China: Implications for controlling eutrophication and harmful algal blooms, Journal of Freshwater Ecology, (30), pp. 5–24. Pandey J, and Verma A (2004) The influence of catchment on chemical and biological characteristics of two freshwater tropical lakes of southern Rajasthan, Journal of Environmental Biology, 25(1), pp. 81-87. Pandey J, and Yaduvanshi MS (2005) Sediment Dredging as a Restoration Tool in Shallow Tropical Lakes: Cross Analysis of Three Freshwater Lakes of Udaipur, India, Environmental Control in Biology, 43 (4), pp. 275-281. Pandey J (2011) The Influence of Atmospheric Deposition of Pollutants in Cross-Domain Causal Relationships, as for Three Freshwater Lakes in India, Lakes & Reservoirs: Research and Management, Blackwell Publishing Asia Pty Ltd, DOI: 10.1111/j. 1440-1770.2011. 00456.x, pp 113-121. Pandey U, and Pandey J (2013) Impact of DOC trends resulting from Changing Climatic Extremes and Atmospheric Deposition Chemistry on Periphyton Community of a Freshwater Tropical Lake of India, Biogeochemistry, Springer Science, DOI 10.1007/s 10533-012-9747-7, pp. 537-553. Parparov A, Hambright KD (2007) Composite water quality: evaluation and management feedback, Water Quality Research Journal of Canada 42 (1), pp. 18–23. Parparov A, Hambright KD, Hakanson L, Ostapenia A (2006) Water quality Quantification: Basics and Implementation, Hydrobiologia 560(1) pp. 227-237. DOI: 10.1007/s10750-005-1642-y. Pearl HW, Fulton RS, Moisander PH, & Dyble J (2001) Harmful Freshwater Algal Blooms, With an Emphasis on Cyanobacteria, The Scientific World, 1, pp. 76-113. doi: 10.1100/tsw.2001.16 Ramachandran K (2001) Assessment of contamination of Natural Resource using GIS and Remote Sensing – a study of Hyderabad region, GIS India, pp. 8 –13. Rhazi LP, Grillas AM, Toure and TanHam L (2001) Impact of land use in catchment and human activities on water, sediment and vegetation of Mediterranean temporary pools, Comptes rendus Académie Sciences, Paris (Life Science), 324, pp. 165-177. Rhodes CJ (2013) Peak phosphorus–peak food? The need to close the phosphorus cycle. Science Progress , 96 (2), pp.109-152. Sahai R, and Sinha AB (1969) Investigation on Bio-ecology of Inland water of Gorakhpur (U.P.) India, Hydrobiologia, (Springer), Volume 34 Issue 3-4, Pp 433-447, Doi.org/10.1007/BF00045402. Salman MA, Nomaan MSS, Sayed S, Saha A, & Rafiq MR (2021) Land use and land cover change detection by using remote sensing and gis technology in Barishal District, Bangladesh. Earth Sci Malaysia, 5(1), 33-40. Sánchez E, Colmenarejo MF, Vicente J, Rubio A, Garcia MG, Travieso L, Borja R (2007) Use of the water quality index and dissolved oxygen deficit as simple indicators of watersheds pollution, Ecological Indicators, Elsevier, 7, pp. 315–328, doi: 10.1016/j.ecolind.2006.02.005. Sawyer CN (1954) Factors involved in disposal of sewage effluents to lakes, Sewage, and Industrial Wastes, 26: 317-325. Schindler DW, Hecky R, Findlay D, Stainton M, Parker B, Paterson M, Kasian S (2008) Eutrophication of lakes cannot be controlled by reducing nitrogen input: results of a 37-year whole-ecosystem experiment, Proceedings of the National Academy of Sciences, 105(32), pp. 11254-11258. Sheergojri, I. A., Rashid, I., Aneaus, S., Rashid, I., Qureshi, A. A., & Rehman, I. U. (2023). Enhancing the social-ecological resilience of an urban lake for sustainable management. Environment, Development and Sustainability , 1-26. Singh, A and Sharma, V.N. (2018), A Stewardship of Ramgarh Lake in Gorakhpur District: Uses, Problems and Management, Transaction, Indian Institute of Geographers, Vol. 40, No. 1, pp. 33-43. Singh, A. and Sharma, V.N. (2019), A comparative assessment of anthropogenic pressure and Trophic Levels of urban (Ramgarh lake) and rural (Chilua lake) lakes of Gorakhpur District, U.P., National Geographical Journal of India, Vol. 65 No. 4, pp. 340-349. Singh A, & Sharma VN (2022) Anthropogenic impacts on lakes and measurement of Trophic Level: A comparative study of Ramgarh (Urban) and Chilua (Rural) Lakes of Gorakhpur District, UP. National Geographical Journal of India, 65(4), 340-349. Singh A, and Sharma VN (2020) An empirical comparative study of changing utilization pattern and problems of rural and urban lakes of Gorakhpur, India, National Geographical Journal of India, DOI: 10.48008/ngji.1748. Singh A, Sharma VN, & Rana NK (2024) Analysis of morphological change of lentic water bodies by using spatial vulnerability index (SVI) in Tarai region of Rapti river plains, India. Geology, Ecology, and Landscapes, 1-11. Søndergaard M, Jeppesen E, & Fjord Aaser H (2000) Neomysis integer in a shallow hypertrophic brackish lake: distribution and predation by three-spined stickleback (Gasterosteus aculeatus). Hydrobiologia, 428, 151-159. Srinath EG, and Pillai SC (1966) Phosphorus in Sewage, Polluted Waters, Sludges, and Effluents, The Quarterly Review of Biology, Vol. 41, No. 4, pp. 384-407. Taube CM (2000) Instructions for winter lake mapping, Chapter 12 in Schneider, James, C., (ed.), (2000), Manual of fisheries survey methods II: with periodic updates, Michigan Department of Natural Resources, Fisheries Special Report 25, Ann Arbor. Wade PM (1999) The impact of human activity on the aquatic macroflora of Llangorse Lake, South Wales, Aquatic Conservation Marine Freshwater Ecosystem, pp. 441-459 (1999). Webster CJ (1995) Urban Morphological Fingerprints, Environment, and planning, (22) pp. 279-297. Weng Q (2001) A remote sensing–GIS evaluation of urban expansion and its impact on surface temperature in the Zhujiang Delta, China, International Journal of Remote Sensing, vol. 22, no. 10, pp. 1999–2014. Wetzel RG (1992) Gradient-dominated ecosystems: sources and regulatory functions of dissolved organic matter in freshwater ecosystems. Hydrobiologia , 229 , 181-198. Wetzel RG (2001) Limnology, Lake, and River Ecosystems. Academic Press, New York, pp 1006, 3rd Edition - ISBN: 9780127447605. Williams WD (1999) Salinization: A major threat to water resources in the arid and semi-arid regions of the world, Lakes Reservation, Research Management, 4, pp. 85-91. Li X, Sha J, & Wang ZL (2017) Chlorophyll-a prediction of lakes with different water quality patterns in China based on hybrid neural networks. Water, 9(7), 524. Yadav A and Pandey J (2017) Contribution of point sources and non-point sources to nutrient and carbon loads and their influence on the trophic status of the Ganga River at Varanasi, India, Environmental Monitoring Assessment, Springer, pp. 189-475, DOI 10.1007/s10661-017-6188-8. Yang J, Lv H, Liu L, Yu X, & Chen H (2016) Decline in water level boosts cyanobacteria dominance in subtropical reservoirs. Science of the Total Environment, 557, 445-452: doi:10.1016/j.scitotenv.2016.03.094. Yang S, Lu J, Chen X, Hou X, Wei Z, and Wu J (2023) Unraveling environmental influences on the spatial and temporal dynamics of cyanobacterial blooms in Lake Erhai during its early stage of eutrophication. Geo-Spatial Information Science, pp.1-19. Yeh AG, and Li X (2001) The measurement and monitoring of urban sprawl in a rapidly growing region using entropy, Photogrammetric Engineering & Remote sensing, vol. 67, No.1, pp. 88-90. Zhong S, Geng Y, Qian Y, Chen W, & Pan H (2019) Analyzing ecosystem services of freshwater lakes and their driving forces: the case of Erhai Lake, China. Environmental Science and Pollution Research, 26, 10219–10229. doi:10.1007/s11356-019-04476-9. Zou W, Zhu G, Cai Y, Xu H, Zhu M, Gong Z, ... & Qin B (2020) Quantifying the dependence of cyanobacterial growth to nutrient for the eutrophication management of temperate-subtropical shallow lakes. Water Research, 177: 115806. doi:10.1016/j.watres.2020.115806. Table 4 and 5 Table 4 and 5 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table4and5.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 18 Jul, 2025 Reviews received at journal 28 Jun, 2025 Reviewers agreed at journal 10 Jun, 2025 Reviews received at journal 09 Jun, 2025 Reviewers agreed at journal 08 Jun, 2025 Reviewers agreed at journal 08 Jun, 2025 Reviewers invited by journal 08 Jun, 2025 Editor assigned by journal 16 May, 2025 Submission checks completed at journal 16 May, 2025 First submitted to journal 24 Apr, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6523182","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":468352019,"identity":"4e9c8d96-7e35-465f-a83a-bc81b46407e6","order_by":0,"name":"Dr. Alka Singh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABFElEQVRIiWNgGAWjYDACdjYgYQBEEjwMDAkVEnIgwQMP8GlhRtby4IyFMVhLAkEtDBAtjA/bKhIbQDx8Wvib2RI//ii4Y7dduveYRAKbRPr8sMMPgbbYyek2YNcicZjtsDSPwbPknXPOpUkk8EjkbrydZgDUkmxsdgCHNYfZG6QZDA4nG9zIMZNIkABqmZ0A0nIgcRsOLfKH2Zt//oBrMZBIN5yd/gGvFoPDbMckeAwO20G0JEgkyEvn4LfF8DBbmjVQS4LBnTPGFgkHJAw3SOcUHEgwwO0XueNtxjd//Dlsb3C7x/Dmz3918vKz0zd/+FBhJ4fT+1AAiQ6wU8EqDfArBwF7OEu+AbeqUTAKRsEoGJkAAAgVY6RedAajAAAAAElFTkSuQmCC","orcid":"","institution":"National Council of Educational Research and Training","correspondingAuthor":true,"prefix":"Dr.","firstName":"Alka","middleName":"","lastName":"Singh","suffix":""},{"id":468352020,"identity":"6f2dcee5-5908-4f62-9d73-8eb80c1ba942","order_by":1,"name":"Prof. Vishawambhar Nath Sharma","email":"","orcid":"","institution":"Banaras Hindu University","correspondingAuthor":false,"prefix":"","firstName":"Prof.","middleName":"Vishawambhar Nath","lastName":"Sharma","suffix":""},{"id":468352021,"identity":"1910ab56-1c0c-4929-b0e0-f6ef18f22362","order_by":2,"name":"Prof. Narendra Kumar Rana","email":"","orcid":"","institution":"Banaras Hindu University","correspondingAuthor":false,"prefix":"","firstName":"Prof.","middleName":"Narendra Kumar","lastName":"Rana","suffix":""},{"id":468352022,"identity":"ddd8fed7-c04d-4242-a315-855bb22ec019","order_by":3,"name":"Ms. Ku Shiwani","email":"","orcid":"","institution":"Banaras Hindu University","correspondingAuthor":false,"prefix":"Ms.","firstName":"Ku","middleName":"","lastName":"Shiwani","suffix":""},{"id":468352023,"identity":"88f5bcc7-fe4b-4371-a6a9-a8948eec9d51","order_by":4,"name":"Mr. Chandrakesh Maury","email":"","orcid":"","institution":"Banaras Hindu University","correspondingAuthor":false,"prefix":"Mr.","firstName":"Chandrakesh","middleName":"","lastName":"Maury","suffix":""}],"badges":[],"createdAt":"2025-04-24 18:38:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6523182/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6523182/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84365981,"identity":"fdf95333-ec3c-4c87-8424-16f43d9cebf6","added_by":"auto","created_at":"2025-06-11 06:07:11","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":871955,"visible":true,"origin":"","legend":"\u003cp\u003eLocation of Chilua Lake in Indian sub-continent and sample sites\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/f99d16e7e1e01de18a52aa70.png"},{"id":84366901,"identity":"90513498-3222-4eb6-86c3-e0aa1304f26c","added_by":"auto","created_at":"2025-06-11 06:15:11","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":497935,"visible":true,"origin":"","legend":"\u003cp\u003eRivers surrounds Chilua Lake in Tarai region, India\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/3c20d47600624741f90c579e.png"},{"id":84365984,"identity":"3ac9e55a-886a-4691-962c-5236b8294eb4","added_by":"auto","created_at":"2025-06-11 06:07:11","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1243885,"visible":true,"origin":"","legend":"\u003cp\u003eMorphometric features of the lake: area, circumference, average depth, fetch volume, maximum length, and maximum width.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/25cf1492fa41e915e78d6ca2.png"},{"id":84367921,"identity":"e3e265ed-eb6f-4510-bd76-ff41a4585569","added_by":"auto","created_at":"2025-06-11 06:31:11","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":276920,"visible":true,"origin":"","legend":"\u003cp\u003eReduction in Extent of Chilua Lake over the years 1922 –2019\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/d1134b1403344f3978694f63.png"},{"id":84367227,"identity":"587f8470-6c95-4e3a-94f3-f5dcd1e09efc","added_by":"auto","created_at":"2025-06-11 06:23:11","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2047076,"visible":true,"origin":"","legend":"\u003cp\u003eEncroachment in extent of Chilua Lake. Images captured by authors during field visit (a, b), and Google earth image (c).\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/22be870033ab5e4b888bb277.png"},{"id":84365996,"identity":"8f26cbef-4f7d-41cd-b869-37b475b1b447","added_by":"auto","created_at":"2025-06-11 06:07:12","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":2178101,"visible":true,"origin":"","legend":"\u003cp\u003eChange in Extent of Chilua Lake during pre-monsoon and post-monsoon, 2019\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/23596e8d46f36659462d6baf.png"},{"id":84365989,"identity":"56018e55-7a98-4bc9-9693-bb73d4a2f593","added_by":"auto","created_at":"2025-06-11 06:07:11","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1265721,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/0b0a17609b30f3f5eb5b8155.png"},{"id":84365991,"identity":"33edfad3-be4f-48b3-aca0-564599878fd2","added_by":"auto","created_at":"2025-06-11 06:07:11","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1582333,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/b93598f4d984099dbe320a56.png"},{"id":84366911,"identity":"c06f5521-d23b-49a6-93ac-82d58903b6b3","added_by":"auto","created_at":"2025-06-11 06:15:12","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":1147042,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/fdc0fa984eedf65d30cfbc9b.png"},{"id":84366909,"identity":"0688f70d-5c43-4dcc-95d8-dd9bb3dae1a7","added_by":"auto","created_at":"2025-06-11 06:15:12","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":1651708,"visible":true,"origin":"","legend":"\u003cp\u003eSewage enter point location in Chilua lake\u003cstrong\u003e (\u003c/strong\u003eGPS location during field observation, 2019 and mapped in GIS environment)\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/c74039dd494bdca83ef6e68b.png"},{"id":84366000,"identity":"086fbcec-8039-4b30-86fb-c009b93481ba","added_by":"auto","created_at":"2025-06-11 06:07:12","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":2498213,"visible":true,"origin":"","legend":"\u003cp\u003eEconomic activities (farming and boating) and religious ceremonies along and on the bed of Chilua Lake by local people (Images captured by authors during field visit)\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/7b0b34cbba3053b22d737ef7.png"},{"id":84366914,"identity":"f864c62c-7443-45bd-9567-cfd50e238981","added_by":"auto","created_at":"2025-06-11 06:15:13","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":525366,"visible":true,"origin":"","legend":"\u003cp\u003eBuilt-up activities on 500 meters buffer zone around Chilua Lake within 15 years (2004 -2019) and prepared by researchers from Google Earth Image 2019 in GIS environment\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/868355d3fcdceb14f33596fb.png"},{"id":84366912,"identity":"bb2ad947-ab8a-45fc-8ec7-be8a9090e1c6","added_by":"auto","created_at":"2025-06-11 06:15:12","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":221744,"visible":true,"origin":"","legend":"\u003cp\u003eLevel of Eutrophication into Chilua Lake water (Trophic Status Index based on Secchi depth, Chlorophyll and Total phosphorus)\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/2ed50ea544c177c25baa3219.png"},{"id":84368700,"identity":"ca0a5aed-ffd0-4180-b1c6-e3bc43b58b61","added_by":"auto","created_at":"2025-06-11 06:39:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":23857746,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/463230e5-16d1-42f2-861b-30413f0882dc.pdf"},{"id":84365980,"identity":"88bdb2b8-53d8-4144-b466-f2d81d753d77","added_by":"auto","created_at":"2025-06-11 06:07:11","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":24735,"visible":true,"origin":"","legend":"","description":"","filename":"Table4and5.docx","url":"https://assets-eu.researchsquare.com/files/rs-6523182/v1/fc1c3317da7a51de3933af3c.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Using Geographic Information Systems (GIS) to Assess Lake Morphometry, Siltation-Induced Ecological Deterioration, and Land Use/ land cover practices on the Dry Bed of Chilua Lake, Tarai Region, India","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eLakes provide water for domestic use, drinking, agriculture, industry, and energy generation (Hyangya et al., 2021), and act as sinks for sediment and contaminants, thereby protecting downstream areas (Oskars et al., 2019). Most human communities surrounding lakes in developing countries are heavily dependent on lake biota (Jeppesen et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) and the natural processes of lakes for water, food, fibre, and livelihoods. However, as populations grow, lake resources come under increasing pressure (International Lake Environment Committee, 2005). In the age of climate change and rapid urbanisation, porous land surfaces such as bare soil and lake ponds are being transformed into impervious concrete surfaces. This transformation blocks the infiltration process, reducing groundwater recharge and increasing surface runoff (Albert et al., 2021). These changes are the by-products of deforestation and soil compaction caused by the covering of bare soil. Due to both natural and human causes, gradual siltation on the lake bottom has increased (Birk et al., 2020), limiting the lake\u0026rsquo;s capacity to store water year-round. Often, the dry lake bed is used for various natural and anthropogenic practices, which increases the potential for encroachment (Singh et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Large amounts of silt deposition affect the morphometric properties of lakes. As a result, lakes gradually develop shallower depths, reduced extents, lower basin volumes (Meza et al., 2022), and an increasing shoreline development index (DL). Nutrients deposited along with silt are a consequence of human activities such as urbanization, agriculture, and industrialisation (Ansari et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Downing et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). Continuous nutrient accumulation in surface water bodies accelerates algae and aquatic weed growth, leading to eutrophication (Alcocer, 2025; Pearl et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Eutrophication results from the fertilization of aquatic ecosystems (Zou et al., \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Its most common feature is increased algal biomass, which often appears as layers of green algae on the water surface (Heino et al., 2021). This growth reduces water clarity (Li et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), interferes with oxygen mixing, and limits oxygen availability for aquatic organisms (Yang et al., \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Trophic status is a multidimensional concept that includes nutrient concentration, nutrient loading, productivity, floral and faunal diversity, and morphometric characteristics of water bodies (Schindler et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Lakes are often affected by abrupt environmental changes caused by anthropogenic activities including industrial, agricultural, recreational, religious, and washing activities, along with solid and sewage waste disposal (Zhong et al., \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Remote sensing and Geographic Information Systems (GIS) techniques are useful in analyzing Google Earth images to study seasonal use of lake beds through classification, mapping, monitoring, and spatio-temporal assessment (Salman et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The uncontrolled growth of the human population has placed severe pressure on lakes, rendering them non-potable, deteriorating water quality, impairing absorption capacity, disrupting aquatic biodiversity, and ultimately leading to the extinction of water bodies (Yang et al., \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The shrinking, pollution, and disappearance of these surface water bodies threaten sustainability, reduce water availability for human use, and endanger wildlife (Ramsankaran et al., 2023). Eventually, the extinction of these water bodies diminishes groundwater recharge (Ramchandran, 2001). Many water bodies\u0026mdash;rivers, lakes, ponds, and canals\u0026mdash;have lost their identity due to unregulated urbanization, lack of embankments, poor coordination among government agencies, and limited public participation in maintenance programs (Peker et al., 2019). In recent decades, water bodies in the Tarai region have suffered severe degradation in both water quality and watershed area. Consequently, communities around lakes experience acute problems like waterlogging and disease outbreaks during the rainy season. Lake shallowness has become a common issue due to surface runoff, stormwater runoff, agricultural runoff, flooding, and mismanagement of sewage systems in residential and remote regions (Jian et al., 2025). Aquatic weed overgrowth and human encroachment, such as constructing built-up areas on dry lake beds, further deteriorate such lake\u0026rsquo;s physical appearance and ecological health (Martin, 2014). Therefore, this study aims to examine the degradation in extent and water quality of Chilua Lake and the increasing built-up and encroachment activities in its surroundings. The major objectives of the study are: (1) To analyze changes in Chilua Lake\u0026rsquo;s morphometry from1922 to 2019 (2) To measure seasonal changes in the extent of the lake (3) To analyze land use practices on the dry bed of the lake (4) To examine the physicochemical status of lake water at various sites based on the level of anthropogenic interference, and (5) To discuss the key factors responsible for ecological deterioration in Chilua Lake.\u003c/p\u003e"},{"header":"2. Material and methods","content":"\u003cdiv id=\"Sec3\"\u003e\n \u003ch2\u003e2.1. Study Lake\u003c/h2\u003e\n \u003cp\u003eChilua Lake (26\u0026deg;49\u0026apos;15\u0026apos;\u0026apos; to 26\u0026deg;56\u0026apos;50\u0026apos;\u0026apos;; 83\u0026deg;20\u0026apos;9\u0026apos;\u0026apos; to 83\u0026deg;25\u0026apos;56\u0026apos;\u0026apos;) is an oxbow lake of the Rapti River in the northeastern region (Singh 2020) of Uttar Pradesh, India (Fig. 1). It is fed by the Chilua Nadi (river) and extends approximately 19,000 meters through a narrow channel. Typically, the lake remains dry throughout the year due to insufficient embankments and shallowness of the basin, except during the monsoon season. The Chilua River, which traverses through the Chilua Lake, originates from the southern foothills of the Himalayas and ultimately discharges into the Rohini River. The genesis of Chilua Lake is associated with complex fluvial processes that have resulted in significant morphometric alterations over time. The Rohini River subsequently converges with the Rapti River, which in turn merges with the Ghaghra River, forming a part of the larger Gangetic River system. Chilua Lake functions as a natural reservoir, playing a crucial role in the temporary storage of excess monsoonal runoff, particularly during flood events in the Rohini and Rapti Rivers. During such events, surplus water from the Rohini River flows into the Chilua Nadi, contributing to the accumulation of water in the basin. This process causes annual bank erosion along the Chilua River, gradually reshaping the terrain and expanding the shallow basin, which eventually led to the formation and growth of Chilua Lake. Other significant streams in the area include Kuwano and Ami (Fig. 2).\u003c/p\u003e\n \u003cp\u003eThe lake is situated in the Himalayan foothills of Indian subcontinent at an elevation of 84 meters above mean sea level (Singh 2018, 2019). Chilua Lake receives approximately 1138.37 mm of rainfall during the rainy season, with a monthly average temperature of 22\u0026deg;C (approximately 11\u0026deg;C in winter and 31\u0026deg;C in summer), and an average relative humidity of 68%. These weather conditions clearly depict the humid Tarai region. In the Himalayan foothills, the Bhabar zone consists of coarse debris that allows water to percolate into the ground, whereas in the Tarai zone, finer soil causes groundwater to reappear at the surface. This results in high groundwater levels and frequent waterlogging problems in the region. The lake serves as a vital resource for local livelihoods, providing a rich habitat for diverse fish species and supplying water for agricultural activities, domestic consumption, and irrigation.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\"\u003e\n \u003ch2\u003e2.2. Acquisition of Lake Morphometric Parameters\u003c/h2\u003e\n \u003cp\u003eThe morphometric characteristics of lentic ecosystems, including surface area, average depth, maximum depth, circumference, volume, maximum length, and maximum width are significant parameters for assessing the physical and ecological status of lakes (Wetzel, 1992; Kalff, 2002). The surface area of a lake defines its horizontal extent (Jorgensen, 2013). Average depth provides insights into the productivity and biological communities of a lake, as shallow lakes typically support more aquatic organisms than deeper ones. Circumference delineates the boundary between the lake and its surrounding environment and serves as an indicator of potential siltation from surface runoff. Lake volume, calculated as the product of average depth and surface area (Taube, 2000), indicates the lake\u0026apos;s capacity to dilute incoming materials. Maximum length and width describe the lake\u0026apos;s spatial dimensions, influencing wave dynamics and sediment resuspension (Wetzel, 1992). The \u003cem\u003emaximum length\u003c/em\u003e is the maximum distance between any two distant points on the \u003cem\u003eshoreline\u003c/em\u003e without intersecting a landmass. The larger the \u003cem\u003emaximum length\u003c/em\u003e, the larger the waves, and the greater the potential for mixing and disruption of bottom sediments. Maximum width is measurement of the maximum wideness between two points on the \u003cem\u003eshoreline\u003c/em\u003e (Wetzel 1992).\u003c/p\u003e\n \u003cp\u003eThe surface area change in Chilua Lake over a 97-year period (1922\u0026ndash;2019) was determined by the comparing the digitized layers of lake area from Survey of India toposheets of the year 1922 on (toposheet no. 63 N on scale of 1: 250000) and 2004 (toposheet no. 63N/5, and 63N/6 on the scale of 1: 50000), and from Google Earth Pro (www.googleearth.com) for the year 2019 in QGIS 3.10 software using WGS 1984 datum and Universal Transverse Mercator (UTM) Projection. L\u003cem\u003eake extent, circumference, maximum length, and maximum width\u003c/em\u003e and the parameters such as \u003cem\u003elake volume, shoreline development and volume development\u003c/em\u003e were calculated using standard formulae within the QGIS Field Calculator. The depth of the lake was measured through an instrumental survey using a boat, a distance measuring tape, and a plumb-bob. Measurements were taken during both May (dry season) and September (wet season), and the final average depth was calculated using the following equation:\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eAverage depth of lake = (Max\u003c/strong\u003e \u003csub\u003e\u0026nbsp;\u003cstrong\u003edepth\u003c/strong\u003e\u0026nbsp;\u003c/sub\u003e \\(\\:+\\:\\)\u003cstrong\u003eMin\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003edepth\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e)\u003c/strong\u003e\u003cstrong\u003e/2\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;. Eq.\u0026nbsp;1\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eWhere, \u003cem\u003eMax\u003c/em\u003e\u003csub\u003e\u003cem\u003edepth\u003c/em\u003e\u003c/sub\u003e: \u003cem\u003eMaximum depth\u003c/em\u003e (m) and \u003cem\u003eMin\u003c/em\u003e\u003csub\u003e\u003cem\u003edepth\u003c/em\u003e\u003c/sub\u003e: \u003cem\u003eMinimum depth\u003c/em\u003e (m).\u003c/p\u003e\n \u003cp\u003eDepth measurements were further validated through responses from sixty local residents whose livelihoods depend on the lake for various purposes (Table 2.2).\u0026nbsp;\u003c/p\u003e\u0026nbsp;The volume of the lake (m\u0026sup3;) was measured using Eq. 2 (Taube, 2000):\u003cp\u003e\u003cstrong\u003eVolume\u0026thinsp;=\u0026thinsp;Surface extent of lake water \u0026times; Mean depth of lake\u003c/strong\u003e \u0026hellip;\u0026hellip;\u0026hellip;. Eq. 2\u003c/p\u003e\n \u003cp\u003eThe \u003cstrong\u003eshoreline development index (D\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eL\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e)\u003c/strong\u003e reflects the degree of shoreline irregularity compared to a perfect circle (Hutchinson, 1957). Lakes with higher D\u003csub\u003eL\u003c/sub\u003e values are more likely to accumulate silt through surface runoff. It is calculated using lake extent and circumference as follows (Table 2.1 and 3):\u003c/p\u003e\n \u003cdiv\u003e\n \u003cp\u003e\u003cstrong\u003eTable 1.\u0026nbsp;\u003c/strong\u003eSurface Extent of Chilua Lake from 1922 to 2019\u003c/p\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"600\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eTime\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eArea (meter\u0026sup2;)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eChange in area (meter\u0026sup2;)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eEncroachment of extent (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e1922\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e13801204.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026hellip;\u0026hellip;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e2004\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11683340.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2117864.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e15.37\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e2019\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e9975504.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1707835.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e11.31\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003eSource: Computed by authors from the digitization of the lake in GIS environment\u003c/p\u003e\n \u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 2.1\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eShoreline Development (D\u003csub\u003eL\u003c/sub\u003e) of Lake Chilua (2019)\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eName of lake\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eArea in m2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eL (circumference)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2\u0026pi;A\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eD\u003csub\u003eL\u003c/sub\u003e= L/2 ѵ\u0026pi;A\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChilua\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9975504.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e68387.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11193.11798\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.109648887\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003eSource: Computed by authors from the digitization of the lake in GIS environment\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003ctable border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 2.2\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eVolume Development (D\u003csub\u003eL\u003c/sub\u003e) of Lake Chilua (2019)\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eName of lake\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eArea in m2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage depth in meter\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum depth in meter\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eZa\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e(0.33Zm) A\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDv\u0026thinsp;=\u0026thinsp;zA/(0.33Zm) A\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChilua\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9975504.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.7432\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.572\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e27332880.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15669233.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.744366234\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cdiv\u003e\n \u003cp\u003e\u003cstrong\u003eTable 2.3\u0026nbsp;\u003c/strong\u003eIndex of Basin Permanence (IBP) of Lake Chilua (2019)\u003c/p\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"717\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eName of lake\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSL (Shorelength)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAverage depth\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eArea in m2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eVolume (Av. depth*Area)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eIBP= V/SL\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eChilua\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e68387.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.7432\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e9975504.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e28489515.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.416587815\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eSource: Computed by authors from the digitization of the lake in GIS environment\u003c/p\u003e\n \u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 3\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eChanges in the morphometric parameters of the lake over the years 1922\u0026ndash;2019\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eChilua lake\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eArea in m2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCircumference in meter\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMax. length in meter\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMax. width in meter\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eShoreline Development (D\u003csub\u003eL\u003c/sub\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1922\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13801204.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e60302.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6344.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1072.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.580175013\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePre-monsoon in 2019\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9975504.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e68387.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6113.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1043.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.109648887\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePost- monsoon in 2019\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18335403.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e85988.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7289.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2328.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.666276956\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\"\u003eSource: Computed by authors from the digitization of the lake in GIS environment\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cimg src=\"data:image/png;base64,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\"\u003e\u003c/p\u003e\n \u003cp\u003eWhere \u003cem\u003eL\u003c/em\u003e is the \u003cstrong\u003ecircumference (m)\u003c/strong\u003e and \u003cem\u003eA\u003c/em\u003e is the \u003cstrong\u003elake area (m\u0026sup2;)\u003c/strong\u003e.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTable 6.\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eUtilization pattern of rural (Chilua) and urban (Ramgarh) lake (1980, 2004, 2019)\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"375\" class=\"fr-table-selection-hover\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eActivities in Chilua Lake\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e1980\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2004\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2019\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eFishing\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e83.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eIrrigation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e53.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e91.66\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eRecreation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e85\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eReligious Activities\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e66.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eDumping Sites\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e31.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e65\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eCattle bathing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e85\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eBoating\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e28.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e53.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eCereals cropping\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e66.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e91.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eVegetable cropping\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eWashing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e53.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e11.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003ecooking and Drinking\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e8.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eSilt use\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e33.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e46.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eVermiculture\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 50px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e16.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 68px;\"\u003e\n \u003cp\u003e23.33\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eSource: People\u0026apos;s responses in percent during field survey (2019)\u003c/p\u003e\n \u003cp\u003eVolume development (DV) is an indicator used to assess the deviation of a lake basin\u0026rsquo;s shape from a conical form to a flat, shallow basin. It is calculated using the maximum depth (Zmax) and the average depth (z) of the lake. For most lakes, DV\u0026thinsp;\u0026gt;\u0026thinsp;1 indicates a deviation from the ideal conical shape, representing a more irregular or flattened basin (Hutchinson, 1957). DV values are typically higher in shallow lakes with flat bottoms (Table 2.1). The parameter is calculated using Eq.\u0026nbsp;4:\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eDV\u0026thinsp;=\u0026thinsp;Za/(0.33\u0026times;Zm) A\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;Eq 4\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eWhere Dv\u0026thinsp;=\u0026thinsp;Volume development, Zm max\u0026thinsp;=\u0026thinsp;Maximum depth, Za\u0026thinsp;=\u0026thinsp;Average depth, A\u0026thinsp;=\u0026thinsp;Area of lake surface.\u003c/p\u003e\n \u003cp\u003eThe Index of Basin Permanence (IBP) is a morphometric parameter that reflects the influence of the littoral zone on the volume of the lake basin. Lakes with an IBP value less than 0.1 are typically dominated by rooted aquatic plants, indicating excessive shallowness, deep green water color, and high concentrations of Total Phosphorus (Kerekes, 1977). IBP values ranging from 0 to 1 indicate the lake\u0026rsquo;s proximity to senescence (Kerekes, 1977). The IBP (Table 2.3) is calculated using the volume of the lake and its shoreline development, as shown in Eq. 5:\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eIBP\u0026thinsp;=\u0026thinsp;V / SL \u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip; Eq.\u0026nbsp;5\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eWhere, V\u0026thinsp;=\u0026thinsp;Volume of the lake (m\u0026sup3;) and SL\u0026thinsp;=\u0026thinsp;Shoreline development of the lake.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\"\u003e\n \u003ch2\u003e2.3. Land use/land cover changes\u003c/h2\u003e\n \u003cp\u003eThe dried bed of Chilua Lake has been significantly impacted by agricultural expansion, vermi-culture, and residential encroachment, while the remaining parts of the lake are heavily infested with aquatic weeds, contributing to ecological degradation. To evaluate this deterioration, land use patterns within the dried lakebed were identified and mapped. The process is included identifying distinct land use/ land cover categories, classifying and digitizing them, and analysing their spatial distribution relative to the lake\u0026rsquo;s topography. Land use/Landcover classes were identified by field survey and the identified layer of various classes were digitized from Google Earth Pro (www.googleearth.com) for the year 2004, and 2019 in QGIS software. The results have been further validated using ground truthing, GPS coordinates, and enquiry from local community, providing critical insights into the accuracy and relevance of the findings.\u003c/p\u003e\n \u003cp\u003eLand use change, particularly expansion of settlement was examined through buffer-based encroachment analysis using satellite imageries of 2004 and 2019 within a GIS environment. Data visualization and analysis were carried out using software tools including QGIS, Google Earth Pro, SigmaPlot, and MS Excel. Key indicators such as lake extent encroachment, habitat transformation, and the trophic status of the lake were mapped and assessed.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\"\u003e\n \u003ch2\u003e2.4. Lake Water Quality Assessment\u003c/h2\u003e\n \u003cp\u003eIn Chilua Lake, three sites were selected for water sample collection, each chosen for representing different degrees of anthropogenic influence and assigned symbolic nomenclature (C1, C2, C3). Location 1, the Maheshra Bridge, located in the southwestern part of the lake, was designated as site C1. This site is significantly influenced by anthropogenic activities. It receives sewage from nearby urban areas, detergents from washing activities, and solid waste from religious offerings such as paper, flowers, cloth, and plastic, generated during marriage ceremonies and other socio-cultural rituals (Fig. 11). Location 2 or C2 is characterized by agricultural activities, including paddy, vegetable, and mustard farming (Fig. 11). In contrast, Location 3 or C3, on the other hand, shows minimal or no human interference (Fig. 1). However, due to the absence of embankments along the shoreline, silt through surface runoff freely enters into the lake. As a result, each location is substantially affected by nutrient pollutants and fine silt particles, which gradually increase the thickness of the underlying silt layer. This has led to a progressive shallowing of the lake, accompanied by the spread of littoral aquatic weeds.\u003c/p\u003e\n \u003cp\u003eThe Trophic State Index (TSI) was used to assess the level of eutrophication in the lake, based on Carlson\u0026rsquo;s Index (Carlson, 1977), which incorporates measurements of Secchi depth (SD), Total Phosphorus (TP), and Chlorophyll-a (Chl-a). Total Phosphorus was analyzed using the Olsen method.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eTSI (SD)\u0026thinsp;=\u0026thinsp;10 (6- ln SD/ln 2)\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;.\u0026hellip;.Eq.\u0026nbsp;6\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eTSI (Chl a)\u0026thinsp;=\u0026thinsp;10 (6- 2.04-0.68 lnChl/ln 2)\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;.Eq.\u0026nbsp;7\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eTSI(TP)\u0026thinsp;=\u0026thinsp;10{6-ln(48/TP)/ln2}\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;.Eq.\u0026nbsp;8\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eThe concentration of chemical parameters in the lake water was analyzed to assess the influx of nutrient pollutants and the increasing chlorophyll concentration in aquatic flora. The physio-chemical parameters were examined included TP, Nitrate (NO₃⁻), Biological Oxygen Demand (BOD), Dissolved Oxygen (DO), Chlorophyll-a (Chl a), Gross Primary Productivity (GPP), Chloride, Salinity, Total Dissolved Solids (TDS), Electrical Conductivity (EC), pH, SD, and Surface Water Temperature (Figs. 8 and 9). Water samples were collected in triplicates using pre-sterilized bottles between 07:30 and 10:30 a.m. at three sampling sites (Fig. 3).\u003c/p\u003e\n \u003cp\u003eDissolved oxygen was measured from sub-surface water samples using the modified Winkler method (APHA, 1998), while BOD was determined using an incubator. Phosphate-P was analyzed using the Olsen method, and Nitrate-N was determined using the brucine-sulphanilic acid method. GPP was assessed through the light and dark bottle method combined with the Winkler technique. Chlorophyll-a concentration was measured using standard spectrophotometric procedures (2004). EC, pH, salinity, and TDS were measured using a digital multi-parameter tester (model WA-2017SD).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eThe sequential development of human civilization has led to the deterioration of lake ecosystems across the planet. Silt deposition from surface runoff, agricultural runoff, and sewage sources has gradually reduced lake depth. As a result, many lakes are becoming increasingly shallow and are overrun by aquatic weeds such as water hyacinth, bulrush, and salvinia. This has caused distortions in morphometric parameters, degradation of water quality, and has pushed many lakes toward extinction (Adamczuk et al., \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). The conversion of lakebeds for vegetable and cereal farming, solid waste dumping, and encroachment due to infrastructural development act as contributing factors to the extinction.\u003c/p\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Changes in the morphometric parameters of the lake during 1922\u0026ndash;2019\u003c/h2\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1.a \u003cstrong\u003eMorphometric Analysis\u003c/strong\u003e\u003c/h2\u003e\n \u003cp\u003eThe surface area of Lake Chilua has shifted approximately 100 to 200 meters over a century, from 1922 to 2019. Generally, the course of the oxbow river or channel has also changed. Notably, there has been a remarkable alteration in the extent of surface water in Lake Chilua. This morphometric change is attributed to the Chilua Nadi, which historically converged with the Rohini River. Prolonged seasonal erosion has been observed in the Chilua Nadi during floods from the Rapti and Rohini Rivers, which has altered the course of the Chilua Nadi and shaped the oxbow configuration of the Chilua lentic ecosystem. Currently, the Chilua Nadi feeds into Lake Chilua, and the lake\u0026apos;s outlet reconnecting with the Rohini River as it did in the past (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). The unique morphology of this lake is maintained by the perennial presence of water, creating a rill-like channel that connects Lake Chilua throughout the year (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea and b). However, the current state of these water bodies supports its classification as a lake primarily due to the post-monsoon coverage of surface water. Consequently, the surface area of Lake Chilua is accurately assessed during the post-monsoon period, while it significantly diminishes during the pre-monsoon phase (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e). Surface water extent of lake Chilua in pre-monsoon is measured as 9975504.46 meter square while it is incraesed during rainy and calculated as 18335403.02 meter square. A huge difference observed from post-monsoon to pre-monsoon (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). This fluctuation indicates a morphometric imbalance and excessive shallowness of the lake in the Tarai region. Such morphometric discrepancies lead to serious concerns regarding the lake\u0026apos;s water quality. Several factors contribute to this issue in the shallow lake, particularly nutrient pollutants like total phosphorus (TP) and nitrate (NO3), which enter the lake from the unembanked shoreline via runoff, leading to silt accumulation. This results in rampant growth of aquatic weeds on the lake bed (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea), further degrading the lake\u0026apos;s ecology as eutrophication levels increase (Karmakar, \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). Therefore, The reducing values of IBP (0.42 which indicate less than 1) and the rise in eutrophication (60 to 80 TSI based on TP and SD) in Lake Chilua indicate ecological degradation (Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e, Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2.3\u003c/span\u003e), characterized by morphometric alterations, which is a significant concern due to the lake\u0026apos;s unique origin. This transformation occurred as the lotic ecosystem of Chilua Nadi transitioned into a lentic ecosystem, namely Chilua Lake, as a result of annual flooding from the nearby Rohini River. Consequently, the irregularities along the shoreline facilitated runoff, allowing nutrient pollutants to enter the lake. As a result, a substantial proliferation of aquatic weeds has been observed on the lake bed, accompanied by a eutrophic to hyper eutrophic status (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1.b. Reduction in lake extent\u003c/h2\u003e\n \u003cp\u003eIn 1922, the area of Chilua Lake was 13801204.56 m\u0026sup2;, and in 2019, the area has decreased to 9975504.46 m\u0026sup2;. There is a noticeable reduction in the extent of Chilua Lake from 1922 to 2019. The decrease suggests a change in the physical size of the lake over the observed period. The loss of area, the difference between the lake\u0026apos;s extent in 1922 and 2019, is 3825700.10 m\u0026sup2; (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) which shows encroachment experienced by the lake bed. 15.37 Percent reduction of lake bed measured in 87 years and 11.31 percent reduction calculated in 15 years. It is clearly shown the anthropogenic pressure or nearby developed urban region on lake zone with the increasing of time period. The encroachment represents the portion of the lake that has undergone changes, potentially due to factors such as urbanization (Fig. \u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e), seasonal land-use/landcover changes (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea and b), or other environmental influences. Such alterations in the lake\u0026apos;s extent can have environmental consequences, affecting ecosystems, aquatic life, biodiversity, water quality and the overall ecological balance of the lake. The reasons behind the reduction in lake area, factors such as human effluents and solid waste dumping (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea), climate change, land-use alterations, and local policies should be considered to better comprehend the dynamics influencing Chilua Lake. It might also be indicative of environmental changes, including issues such as sedimentation, urbanization, or climate-related impacts.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e3.1.c. Current Scenario\u003c/strong\u003e: The morphometric features of the lentic ecosystem (surface extent of lake water, average depth, maximum depth, circumference, volume, maximum length, and maximum width) are measured (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e) to find the deterioration (Wetzel \u003cspan class=\"CitationRef\"\u003e1992\u003c/span\u003e and Kalff \u003cspan class=\"CitationRef\"\u003e2002\u003c/span\u003e). The extent of lake Chilua is 9975504.46 m\u0026sup2;. The average depth of the lake is 2.29 m which reflects that the lake is shallow. The circumference of the lake is 68387.78 m and the volume is 22804003.2 m3. The shoreline development is 6.12. Maximum length is 6113.41m and maximum width of the lake is 1043.12 m whereas fetch of the lake is 3578.26 m (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Lake with larger volume of water, low shoreline and volume development has more remarkable ability to dilute nutrient materials coming into the lake water. The maximum length and maximum with of this lake is also greater in the year of 1922 than in 2019 as well as greater value also calculated during post monsoon then pre monsoon (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eLess than 1 shows more circular and lesser shoreline in distance. Hence, least potential to siltation through surface runoff while greater than 1 reflects larger circumference in in length and more irregular like elliptical, lunate shape of lake occurred. Shoreline development of lake Chilua was measured by 6.109. It clearly shows the shallowed lake basin due to larger circumference and huge distorted from a circular shape. Therefore lake bed has huge potential to enter surface runoff and silt deposition gradually filled the lake basin hence, a blue landscape change into grey and green landscape due to natural as well as anthropogenic actions. Moreover, D\u003csub\u003eL\u003c/sub\u003e of Chliua lake is calculated as 4.580175013 and 6.109648887 (pre-monsoon) in the year of 1922 and 2019 respectively while 5.666276956 measured in post monsoon in 2019. This kind measurement is clearly depicted in earlier time the shoreline distortion is lower than present and potential of siltation through runoff is also lower than present time. As well as increasing value of D\u003csub\u003eL\u003c/sub\u003e found during rainy season (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2.1\u003c/span\u003e). A positive relation is found between shoreline distortion and potential of siltation through runoff. Less than 1 shows the conical volumetric shape of lake basin while the greater than 1 reflects shallow lake. Volume development of lake Chilua was measured by 1.744 (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2.2\u003c/span\u003e). It clearly shows the shallowed lake basin due to distorted shoreline development. This situation of lake invited the huge amount of silt deposition hence, aquatic weeds covered the lake bed and in this way a aquatic habitats altered into terrestrial habitats due to natural and anthropogenic actions (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. Catchment, buffer zone and dry bed land use/land cover\u003c/h2\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2.a. Land uses on the dry bed of Chilua Lake\u003c/h2\u003e\n \u003cp\u003eThe water is available for only few months in the entire lake bed. For 6 to 8 months, the lake goes dry out and the water left behind in patches. Thus, the dried patches are being engaged in various activities by the local people. \u003cem\u003eExtent\u003c/em\u003e of lake bed is covered by (a) stream like storage (20%) in which water is available in all seasons, (b) water left in patches during dry season (15%), (c) littoral plant coverage (45%), (d) farming (11%), (e) dry lake bed (10%), (f) and built-up area (0.3%) (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea and b).\u003c/p\u003e\n \u003cp\u003eThis study explores levels of deterioration in the lake caused by either thick layer of silt deposition (both by natural run off and anthropogenic affluents) or encroachment by locals on lake bed. The lake, being shallow, holds water everywhere from shore to core for 2 to 3 months in rainy season and only 35 percent (15% \u003cem\u003earea\u003c/em\u003e for water bodies and 20% for streams) water remains on lake bed for 8 to 9 months (except rainy season). 75 percent of the lake \u003cem\u003earea\u003c/em\u003e is suffering from spread of littoral plants, anthropogenic encroachment for various activities (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea and b). The growing aquatic littoral floral (water hyacinth, water lily, etc. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e) and siltation are preliminary factors which are gradually pushing the lake ecology towards extinction.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2.b. Spread out of siltation on Chilua Lake bed\u003c/h2\u003e\n \u003cp\u003eThe Chilua Lake is largely influenced by gradual siltation due to natural surface runoff from surroundings, lack of proper embankment, and lack of dredging activity. In the lake basin, vertical siltation also occurs but focused on a major problem which is identified as the horizontal accumulation of silt and severely deteriorating the lake ecology. People have successfully encroached the shallow \u003cem\u003earea\u003c/em\u003e of the lake by agricultural activities, residential encroachment, infrastructural development, etc. and as well as naturally covered through littoral plants on shallow lake beds (Yang et al., \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). The lake zone is filled with water in the rainy season for two or three months but during the remaining month\u0026apos;s lake dry out and thus used for crop and vegetable production, settlement encroachment, some part of land dries out, coverage of aquatic weeds and water in lake remained as patches like water bodies and rill like a channel from source to discharge point in the lake basin (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea and b).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3. Lake Water Quality\u003c/h2\u003e\n \u003cp\u003eNutrients load in deposited silts into lake Chilua are consequence of human activities (Singh et al., 2020), such as increasing urbanization, agriculture, and industrialisation (Downing et al., \u003cspan class=\"CitationRef\"\u003e1999\u003c/span\u003e). Continuous accumulation of nutrients as underlying silt accelerates the production of aquatic weeds, leading to eutrophication (Carlson, \u003cspan class=\"CitationRef\"\u003e1977\u003c/span\u003e and Zou et al., \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e) and analyzed by the BOD, BO, TP, NO\u003csub\u003e3\u003c/sub\u003e, SD, TDS, pH, EC, GPP, Chla, etc. (Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e). The essential feature of eutrophication is increasing littoral biomass, which develops gradual siltation at the root of this prolific flora on surface water. It reduces water clarity and increase shallowness (Li et al., \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e), interrupts the oxygen availability for aquatic organisms (Yang et al., \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). The \u0026lsquo;trophic\u0026rsquo; is a multidimensional concept which includes nutrient concentration, productivity, floral and faunal diversity (Schindler et al., \u003cspan class=\"CitationRef\"\u003e2008\u003c/span\u003e). Lakes are often influenced by anthropogenic activities including industrial, agricultural, recreational, religious, washing, and etc. activities, solid and sewage waste disposal (Zhong et al., \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). Therefore, the trophic status shown the level of eutrophication and ecological deterioration due to gradual siltation and growing of aquatic weeds on dry bed of lake extent.\u003c/p\u003e\n \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\n \u003ch2\u003e3.3.1 Nitrogen and Total Phosphorus concentration\u003c/h2\u003e\n \u003cp\u003eNitrogen and phosphorus are often identified as important limiting factors for algal biomass. The excess input of nutrient pollutants results in the proliferation of planktonic alga and which disrupts the entire aquatic environment. Orthophosphate is one of the forms of P that autotrophs can be assimilate. Excessive production of autotrophs, especially algae and cyanobacteria can lead to eutrophication which pose very serious effect on overall water quality including trophic relationships. The study showed that the Total Phosphorus and Nitrate were recorded highly during summer due to low water level remained after the evaporation and hence high toxicity concentration appeared. Whereas moderate concentration found during winter due low evaporation and huge water remained from rainfall, and low concentration measured during rainy due to dilute the toxicity with huge amount of rainy water in the Chilua Lake. This could be occurred due to anthropogenic influences (sewage source from the city area, washing activity and ceremonies like religious offerings) at C1. The concentration of nutrients pollutants load (TP and NO\u003csub\u003e3\u003c/sub\u003e in mg/L) moderately found at C2 site due to agricultural activity on lake during dry season and along the lake shore. But low concentration of nutrient pollutants (TP and NO\u003csub\u003e3\u003c/sub\u003e) was recorded at C3 site due to lack of any specific kind of anthropogenic interferences (Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e). In winter season, the level of Total Phosphorus a bit moderate relatively less amount of these components entering to the lake. Also, the algal biomass starts to develop algal blooms and algal mats as a layer on the surface of water. In summer season the orthophosphate level declined further due to still excessive use by primary producers together.\u003c/p\u003e\n \u003cp\u003eThe concentrations of TP in mg/L were; 1.10 (winter), 1.47 (summer), 0.99 (rainy) at site C1; 0.015 (winter), 0.045 (summer), 0.009 (rainy) at site C3; 0.93 (winter), 1.24 (summer), 0.87 (rainy) at site C2; respectively (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e and Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). Nitrate is also following the same trend of Dissolve reactive Phosphorus. In the similar way, the values of Nitrate were 7.37 (winter), 8.92 (summer), 7.09 (rainy) at site C1; 6.33 (winter), 7.89 (summer), 6.12 (rainy) at site C2; 1.78 (winter), 2.01 (summer), 1.63 (rainy) at site C3; respectively in rural surrounding Lake Chilua (Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). Tropical lake has been severely influenced by anthropogenic activities which degrade the water quality and also the aesthetic values (Wade, \u003cspan class=\"CitationRef\"\u003e1999\u003c/span\u003e) at site C1 due to receive large quantity of untreated domestic effluents from city region, detergent from washing activity, residue from ceremonies like religious offerings along the lake shore. Whereas agricultural (cereal and vegetable crops) activity done on dry bed of lake extent during summer and winter (Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e) at site C2. Whereas mesotrophic level recorded at C3 due to less anthropogenic activity (Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e\n \u003ch2\u003e3.3.2 Biological Oxygen Demand and Dissolved Oxygen level\u003c/h2\u003e\n \u003cp\u003eThe BOD refers to demand of oxygen for decomposing the organic matter waste through biologically (bacteria) active of living organisms in aquatic ecosystems. In this study BOD level was high in summer due presence of massive algal bloom in the lake. The oxygen is used in decomposition of nutrient pollutant. During rainy season the BOD level remains moderate due to rainfall mediated dilution of organic waste. In winter season the BOD remains low because biodegradation of waste material through bacteria occurs on spatial scale.\u003c/p\u003e\n \u003cp\u003eThe concentration of BOD was recorded in mg/L as 11.92 (winter), 12.89 (summer), 12.06 (rainy) at site C1; 4.98 (winter), 5.96 (summer), 5.24 (rainy) at site C3; 10.28 (winter), 12.07 (summer), 11.53 (rainy) at site C2 respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and Table\u0026nbsp;6). As expected, the DO showed a trend opposite to BOD. It was found to be 5.88 (winter), 5.0 (summer) and 5.34 (rainy) at site C1; 7.98 (winter), 6.33 (summer), 7.14 (rainy) at site C3; 6.09 (winter), 5.09 (summer) and 5.41 (rainy) in mg/L at site C2 respectively in lake Chilua (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and Table\u0026nbsp;4.1). The dissolved oxygen (DO) in water ensures survival of living organism in aquatic ecosystem. It is needed for respiration of fish and other organism in aquatic system. The D.O. enters in freshwater after diffusion from atmosphere and by-product of photosynthesis by algae and other plants. However, epiliminetic waters and shallow lake progressively equilibrate with the atmospheric oxygen concentration. The Lake Chilua is deep lake but low IBP promote the shallow lake beds with huge coverage of aquatic weeds. In this lake, DO was high in winter due to high oxygen holding capacity of water and also rate of decomposing waste. The DO was moderate in rainy season due to dilution effect and high in late summer due to presence of algal mat in lake water. In summer to over-saturation of algal bloom and low oxygen holding capacity of water reduces the DO level and cause problem to surviving biota and may result in fish kill (Singh \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). The DO inversely relates BOD, and accordingly the former is high in winter and moderate in rainy and less in summer season (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e\n \u003ch2\u003e3.3.3 Chlorophyll and Gross Primary Production\u003c/h2\u003e\n \u003cp\u003eThe amount of chlorophyll in urban lake was high in winter due to conducive condition including nutrients whereas in rainy season chlorophyll declined due to dilution effect from rainy water. But it is recorded low concentration in summer due to decomposition of living organism by excess temperature. The concentration of chlorophyll is low in sewage water due to high turbidity coupled less penetration of light. Away from these polluted sites and due to presence of high amount of nutrient the algal bloom grows and proliferate resulting eutrophication condition seen in the lake. Very far away from sewage site and less anthropogenic influences such as the chlorophyll was found low at site C2. The declining nutrient concentration caused reduction in chlorophyll biomass (up to 41.4%) and primary productivity (up to 32.2%) reflecting a reversal of eutrophic status towards oligotrophic. The GPP showed similar trend as Chl a with rapidly declining trend in lake water.\u003c/p\u003e\n \u003cp\u003eThe values of Chlorophyll in mg/L were 19.11 (winter), 10.92 (summer) and 4.09 (rainy) at site C1; 6.89 (winter), 4.01 (summer) and 2.1 (rainy) at site C3; 14.79 (winter), 6.73 (summer) and 4.09 (rainy) at site C2 respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and Table\u0026nbsp;4.1). The GPP followed a similar cause effect relationship and the trends were similar to chlorophyll concentration. In this way, 6.12, 4.43 and 3.9 at site C1; 1.1, 1.02 and 0.9 at C3; 5.48, 3.9 and 3.5 in mg/L at C2 in winter, summer and rainy respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and Table\u0026nbsp;4.1). Secchi depth was high in rainy season and low in summer and moderate in winter. It was recoded as 0.66 (winter), 0.73 (summer) and 0.42 (rainy) at site C1; 1.02 (winter), 1.19 (summer), 0.81 (rainy) at site C3; 0.57 (winter), 0.65 (summer), 0.3 cm (rainy) at site C2 in Chiua lake (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and Table\u0026nbsp;4.1). The increasing concentration of TDS and Chlorophyll represent the decreasing concentration of Secchi depth because it shows the presence of anthropogenic influences (domestic sludge, detergent, residue from ceremonies like religious offerings, etc.).\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e3.3.4 Salinity and Chloride\u003c/em\u003e: The range of salinity which determines the range of chloride in aquatic system is also affected by domestic and industrial effluents. In the Chilua Lake, moderate concentration of chloride as well as salinity could be linked to sewage from city region. Temporally, it was high in rainy due to catchment inflow from surroundings into lake through rainy water. Whereas in summer, chloride and salinity amount was high due to less dilution effect, but it is least recorded in winter due to moderate level of water availability and lack of catchment inflow into lake. Chloride concentration followed a declining trend from sewage water towards remote location (lesser influence of human activity). It was high to low in rainy, summer, and then in winter.\u003c/p\u003e\n \u003cp\u003eThe concentration of Chloride in mg/L was found to be 56.81 (winter), 67.43 (summer) and 63.38 (rainy) at site C1; 48.4 (winter), 53.89 (summer) and 50.27 (rainy) at site C3; 51.41 (winter), 58.29 (summer) and 55.21 (rainy) at site C2 respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e and Table\u0026nbsp;4.2). As expected, the Salinity showed a similar trend to Chloride. It was found to be 196, 200, and 198 NTU at site C1; 165, 162, 169 NTU at site C3; 186, 197 and 181 NTU at site C2 in winter, summer, and rainy respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e and Table\u0026nbsp;4.2).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e\n \u003ch2\u003e3.3.5 Total Dissolved Solids, Electrical conductivity, pH, and Surface Temperature\u003c/h2\u003e\n \u003cp\u003eThe TDS, electrical conductivity, pH, and surface water temperature all remain high in summer followed by rainy and winter respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e and Table\u0026nbsp;4.2). The TDS recorded low at dredging site C1 (321, 426 and 400). Towards north-east, the value increased (109, 126 and 118 at C3; 344, 443 and 423 mg/L at site C2 in winter, summer and rainy respectively. Large amount of suspended particulate matter enters freely into the lake through catchment inflow during rainy season and it is severely affecting the lake beds due to lack of any embankment which prevent the surface runoff from surroundings. Electrical conductivity also followed a similar trend. The values were detected in \u0026micro;s about 506 (winter), 525 (summer) and 516 (rainy); at site C1; 303 (winter), 416 (summer), and 400 (rainy) at site C3; 428, 445 and 433 \u0026micro;s; at site C2 respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e and Table\u0026nbsp;4.2). Therefore, the residue from anthropogenic activity sewage effluents came through seasonal runoff into the lake catchment and increase the concentration of Electrical Conductivity. It is reduced towards the lesser influenced sites by human activity. The pH values again match with these above trends. The pH did appear at 7.21 (winter), 7.25 (summer) and 7.2 (rainy) at site C1; 7.11 (winter), 7.15 (summer), 7.09 (rainy) at site C3; 7.16 (winter), 7.21 (summer), and 7.17 (rainy) at site C2 respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e and Table\u0026nbsp;4.2). This was probably due to the presence of a variety of nutrient pollutants by agricultural runoff, surface runoff, and one sewage runoff from city region. The surface water temperature is recorded in ℃ with very little variation among site and due to sample collection from each site at very small-time interval. Low to high temperature recorded followed the atmospheric temperature trend. Surface temperature was recorded 19.6, 27.7 and 24.3 at site C1; 20.5, 28.6 and 25.7 at site C2; 20.6, 28.9 and 25.9 ℃ at site C3 in winter, summer and rainy season respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4. Responsible factors of siltation in Chilua Lake\u003c/h2\u003e\n \u003cp\u003eThe lake water also mixed with sewage and municipal solid wastes. In the lake bed, some places suffer from high concentration of nutrient pollutants and silts due to dumping of city\u0026rsquo;s solid waste and agricultural activities. The responsible factors of spread out of siltation in the Chilua Lake bed, observed from GIS analysis and field investigation are:\u003c/p\u003e\n \u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(i) Natural and anthropogenic runoff\u003c/strong\u003e: The rural lake is fed by surface runoff, surplus water of Rohini river during flood (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e), agricultural runoff (Singh \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e) and also by the anthropogenic effluents from one sewage entering point (Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e). Dumping the sewage waste into lake is easiest option available to local city dwellers and authorities because the residential soak pits are less successful due to the high ground water level in Tarai region. One sewage source enters near sample site C1 and freely into lake and carried the city area wastes.\u003c/p\u003e \u003cspan\u003e\n \u003cp\u003e\u003cem\u003e(ii)\u003c/em\u003e \u003cstrong\u003eLack of concrete embankment\u003c/strong\u003e: Water stored in shallow lake in all seasons largely depend on the embankment. Chilua Lake has become gradually shallow, and water remains only in patches and rill like channels due to lack of any kind of kachha or pacca embankment which holds the water storage and also prevents lake shore from erosion and checks the entry of the amount of eroded soil (Figs. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e) in lake bottom as silt (Singh \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\n \u003c/span\u003e \u003cspan\u003e\n \u003cp\u003e\u003cem\u003e(iii)\u003c/em\u003e \u003cstrong\u003eEncroachment\u003c/strong\u003e: The \u003cem\u003eextent\u003c/em\u003e of Chilua Lake is reduced up 27.75% in 97 years from 1922 to 2019. Reduction in lake shore is the result of lack of proper boundary demarcation or proper construction of embankment and gradual silt deposition. Hence, the shallow lake bed is filled and covered by aquatic weed (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e and Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003c/span\u003e \u003cspan\u003e\n \u003cp\u003e\u003cstrong\u003e(iv) Circumference of the lake\u003c/strong\u003e: circumference is the way to measure the lake\u0026apos;s openness (Lakewatch \u003cspan class=\"CitationRef\"\u003e2001\u003c/span\u003e). A larger circumference has the larger potential for allowing entry of eroded material or fine silt into the lake zone due to large boundary. Lake Chilua has large circumference (68387.78 m) and poses huge potential of silts deposition through surface runoff due to highly irregular distorted shore (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, Table \u003cspan class=\"InternalRef\"\u003e2.1\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n \u003c/span\u003e \u003cspan\u003e\n \u003cp\u003e\u003cstrong\u003e(v) Land uses/Landcover changes in surrounds\u003c/strong\u003e:\u003c/p\u003e\n \u003c/span\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eLakes are normally healthy, and fruitful for all aquatic organism and many livelihoods for people like agriculture, vegetable cropping, irrigation, cattle bathing, ceremonies like religious offerings, vermiculture and use as drinking water etc. offered which have been catering to the anthropogenic, ecological, and environmental needs in the surrounding. Moreover, some potential uses of lakes are also prominent like forest surrounding the lake, development of aquatic biota, sink for temperature control, polluted water and soil and healthy aquifer. However, as time goes on from 1980 to 2019 and human activity increases, these usefulness changes. In 1980, fishing in Chilua Lake was moderate, but as the population density around the lake expanded, fishing continued to be appropriate untill 2019, but it was not commercially viable due to inadequate government support. There is plenty of space for irrigation around Chilua Lake, but it is primarily used locally due to its mild irrigation. The lake bed region is used to cultivate a range of crops in the winter, such as wheat, mustard, and various vegetables like cauliflower, potatoes, peas, carrots, and more. A total of 60 respondents (100%) confirmed vegetable cropping and agricultural production. They produce for both personal and business purposes. Due to a lack of private or governmental concern about the park, hotel, restaurant, etc., recreational opportunities were extremely limited and utilized exclusively by locals. Locals and others in the vicinity used the lake extensively for ceremonies purpose like religious offerings including Chhat puja, marriage and other social rituals, idol immersion (Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e) during numerous festivals, etc. (Singh \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). Because the livelihood and way of life of the surrounding people depended on natural resources. Dumping sites area on the lake bed increased with the increasing of population number where municipal solid wastes largely dumped from city\u0026apos;s outskirts. As a result, 65 percent dumping activity increased within 39 years. Forty-two people (70%) agreed that there was a lot of cattle bathing on the lake area. Boats were used in Chilua Lake for fishing, gathering fodder crops, and other purposes. The use of washing in Chilua Lake was decrease by local due to increasing shallowness. Brick chimneys set up along the lake and use the sediment deposits of the lake bed. Vermiculture, such as earthworms, thrives and is used by the locals as biofertilizer on agricultural land from the early years (Table\u0026nbsp;6).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(vi) Increasing built-up activities around the lake\u003c/strong\u003e:\u003c/p\u003e\n \u003cp\u003eIn the buffer of 500 m, built-up activities are prohibited as per the National Green Tribunal\u0026rsquo;s guidelines (Kasture \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). Despite this fact, built-up activities including residential, commercial, administrative buildings and other infrastructural development are increasing in the lake zone. These encroachments depict congestion, and pressure of human interference on the lake due to uncontrolled and unplanned development processes. In 500-meter buffer (Fig. \u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e) Chilua Lake is covered by a total area of 9975504.46 m\u0026sup2; and 1.31 per cent area is encroached by built-up activities.\u003c/p\u003e\n \u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(vii) Lack of Monitoring and management of lake\u003c/strong\u003e: The safe guard measures of stewardship such as development of embankment, harvesting of aquatic weeds (Hansson et al., 2018), dredging out of silts, and afforestation rejuvenate the lake from its shallow character. Although some steps of stewardship are initiated in Chilua Lake, significant remedial actions had not been taken yet in any parts of lake zone. Therefore, lake is neglected and keeps on suffering from excess shallowness and littoral plant coverage (Singh \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e and 2024).\u003c/p\u003e \u003cspan\u003e\n \u003cp\u003e\u003cstrong\u003e(viii) Increasing eutrophication in lake water\u003c/strong\u003e: Continuous nutrient buildup as underlying silt speeds up aquatic weed growth, causing eutrophication, which is measured by the TP, SD, Chl a, etc. (Fig. \u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e). Because of the shallow epilimnion lake\u0026apos;s high turbidity, TSI values ranging from 60 to 84 were measured based on Secchi depth. Due to the intake of agricultural fertilizer through free surface runoff, the TSI ranged from 40 to 80 based on TP. Because of the flowery cover on the lake\u0026apos;s bottom floor, 30 to 60 TSI were observed based on Chl a (Fig. \u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e). Anthropogenic activities (agricultural, recreational, religious, washing, etc.) that increase nutrient content, productivity, and floral and faunal diversity in lake water (Schindler et al., \u003cspan class=\"CitationRef\"\u003e2008\u003c/span\u003e). Because of the slow siltation and the growth of aquatic weeds on the dry bed of the lake extent, the trophic status thus indicated the degree of eutrophication and ecological degradation.\u003c/p\u003e\n \u003c/span\u003e\n\n\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e4.1. lake Stewardship and potential uses\u003c/h2\u003e \u003cp\u003eIn recent years, there had been a growing concern over the increasing nutrient pollutant loads and eutrophication in freshwater lakes (Beklioglu \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Pandey and Pandey \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). These changes lead to continuously decline in the amenity, aesthetic enjoyment, recreational value, and quality of freshwater lakes (Sondergaard et al., 2000). Urban rapid development not only increased the rates of sewage discharge and sediment delivery but also encroached the riparian corridors. Surrounding the lake and streamside, mini forest is being developed for the stream stabilization, protection of banks and bed from erosion (Booth et al., 1996). A number of approaches have been examined and proposed all over the world to control eutrophication. Widely accepted method focuses on controlling external nutrients input to control eutrophication (Jeppesen et al., 1999). This approach has been proved effective mostly for deep lakes although less effective for shallow lakes (Beklioglu \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). In recent time, sediment dredging has been used effective approach and tool to bring down the internal flushing of surface to bottom nutrients in shallow lakes (Sondergaard et al., 2000; Pandey and Verma 2005). Sediment dredging removes accumulated nutrients specially phosphate from the bottom layer sediment and supports internal flushing (Jeppesen et al., 1999; Sondergaard et al., 2001) and progressive reversal of the lake health from eutrophic stage to Oligotrophic stage. Sewage treatment plants add phosphorus into surface water bodies (APHA \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1985\u003c/span\u003e and 1998). Normally, an adult excretes (getting rid of solid waste material from human body) 1.3\u0026ndash;1.5 gm of phosphorus every day. Primary treatment removes 10% phosphorus only from the sewage waste; secondary treatment removes 30% only and remaining is discharged freely into water body (Harper \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Rhodes \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Thus, tertiary treatment is essentially required to remove phosphorus from the water. In total, immediate actions are required to conserve and restore the lake ecosystem and its aquatic resources. Protecting existing grassed area and trees in the catchment prevents erosion. Proper treatment of domestic wastes and safe application of fertilizers reduce nutrient\u0026rsquo;s entry into the lake. Other techniques of stewardship are followings:\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Basin lake management techniques (BLMT) include:\u003c/h2\u003e \u003cp\u003eBasin lake management techniques (BLMT) involves (1) Removing excess sediments in lakes which can help eliminate nutrients and aquatic weed growth, deepen area for recreational uses and remove toxic or other contaminated substances (2) Adding aluminium sulphates to lakes which can help to control algae by making phosphorus and the nutrients that drives algal blooms, unavailable for use (3) Stabilizing lake shorelines can decrease sediment\u0026rsquo;s load and turbid conditions in lakes (4) Mechanical removal of excessive grown aquatic plant which increases areas available for recreation, navigation, irrigation and helps removing the source of nutrients released by decaying plants, which can in turn, decrease algal blooms (5) Adding oxygen to a lake through aeration devices which can prevent fish kills, create conditions unfavourable for algal blooms and improve the taste and colour of water (Bronmark \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Specific research for such individual lake for further protection and management of the lakes are needed. In this way, the immediate effect on integrated lake basin management will be seen after implement of Triple-\u0026lsquo;P\u0026rsquo; model. Hence, the Chilua Lake will be comes out from the category of shallow deteriorated eutrophic lake. However, some negative impact can develop after implementation of BLMT for specific lake. Such as, it might be promoting lake beautification as well as visitors\u0026rsquo; attraction and then noticed some solid wastes surrounds lake (Sheergojri et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Triple- \u0026lsquo;p\u0026rsquo; model\u003c/h2\u003e \u003cp\u003eFor restoring of lakes in the study area, \u003cem\u003e\u0026lsquo;Triple- P\u0026rsquo;\u003c/em\u003e model \u003cem\u003eprevention, protection and promotion\u003c/em\u003e can be used for holistic stewardship. 27 indicators of this model (Ban on solid waste dump, detergent use, idol immersion, built up activity surroundings 50 m, make proper embankment, promote afforestation are formulated to steward the lake in the study area (Table\u0026nbsp;5).\u003c/p\u003e \u003cp\u003eAcknowledging the importance of lakes for the living organism, as well as for maintaining the ecological balance for environmental sustainability, the deterioration of lentic ecosystems is matter of concern (Hanazato 2001) due to population pressure and unplanned economic, developmental, and other human activities. The study finds out that the Chilua Lake is largely affected by intense agricultural activities, built-up land encroachment, solid waste dumping, and sewage entry in lake catchment. The study presents a comprehensive understanding of the degradation of Chilua Lake's ecosystem, emphasizing the multifaceted factors contributing to its current status. It delves into various aspects such as morphometric features, reduction in lake \u003cem\u003earea\u003c/em\u003e, land uses on the dry bed, siltation, responsible factors of siltation, and stewardship and potential uses of the lake to understand the complexity of natural processes and human activities shaping the current state of the lake.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThe study identifies natural and anthropogenic runoff, lack of embankments, encroachment of surface extent, large lake circumference, land uses of lake bed, trophic status of lake water and lack of monitoring and management as key factors contributing to siltation in Chilua Lake. The accumulation of silt leads to the shallowing of the lake bed and the proliferation of aquatic weeds, pushing the lake ecology towards extinction based on less than 1 IBP and more than 1 DV. The morphometric features of the lake are analysed, revealing a decrease in \u003cem\u003edepth\u003c/em\u003e and \u003cem\u003evolume\u003c/em\u003e over time. These measurements indicate a shallower body of water, which is more vulnerable to environmental stress. Additionally, the reduction in lake \u003cem\u003earea\u003c/em\u003e over the 97 years is observed, with urbanization, land-use changes, and lack of management strategies being identified as key drivers. This reduction has significant implications for biodiversity, eutrophic status of water quality, and overall ecological balance of the Chilua Lake. The utilization of the dry bed of Chilua Lake for various activities such as farming, settlements, and infrastructure development exacerbates the degradation of the lake ecosystem, further threatening its sustainability. Siltation emerges as a major issue affecting the lake. This study underscores the urgent need for immediate actions to conserve and restore the lake ecosystem. Recommendations include protecting catchment \u003cem\u003earea\u003c/em\u003e, treating domestic wastes, dredging excess sediments, stabilizing shorelines through embankment, and implementing lake management techniques to control aquatic weeds and improve water quality. Overall, the study provides valuable insights into the challenges facing Chilua Lake and other freshwater ecosystems. It advocates the implementation of holistic management approach. By implementing Tripple-P model, basin lake management techniques (BLMT) and engaging local communities, policymaking can be done to work towards preserving and restoring these vital natural resources for future generations.\u003c/p\u003e"},{"header":"6. Research Limitations","content":"\u003cp\u003eA key limitation of this study is the unavailability of historical data for the year 1922, which significantly constrained the analysis of Chilua Lake\u0026rsquo;s morphometric characteristics during that period. Since direct observation or measurement is not feasible for historical conditions, it was not possible to obtain primary data for 1922. Furthermore, no secondary sources were found to contain essential morphometric information such as average depth or volume of the lake. Consequently, critical parameters such as DV, IBP, and average depth could not be calculated for the year 1922. Additionally, the unavailability of boats and poor navigability due to the shallowness of bed of the lake made it impossible to measure depth and the thickness of silt at multiple locations except the three locations during this research study.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets analyzed here were combined with funding from the University Grant Commission, India and laboratory experimentation done in Department of Botany, Banaras Hindu University. We are thankful to all the organizations and people involved in this research work and data collection.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDisclosure statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo potential conflict of interest was reported by the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u003c/strong\u003e: not applicable in this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics, Consent to Participate, and Consent to Publish declarations:\u003c/strong\u003e not applicable in this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the University Grants Commission\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData will be made available if asked and required.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAdamczuk M, Pawlik-Skowrońska B, \u0026amp; Solis M (2020) Do anthropogenic hydrological alterations in shallow lakes affect the dynamics of plankton? Ecological Indicators, 114, 106312.\u003c/li\u003e\n\u003cli\u003eAnonymous (2001) State of Environment Report, India Chapter, United Nations Environment Programme Publications.\u003c/li\u003e\n\u003cli\u003eAnsari AA, Gill SS, \u0026amp; Khan FA (2011) Eutrophication: threat to aquatic ecosystems. Eutrophication: causes, consequences and control, 143-170, DOI 10.1007/978-90-481-9625-8\u003c/li\u003e\n\u003cli\u003eAPHA (1985) Standard Methods for the Examination of Water and Wastewater. \u0026mdash; American Public Health Association. Washington DC. 268 pp.\u003c/li\u003e\n\u003cli\u003eAPHA: Standard methods for the examination of water and wastewater, 20th edition, APHA, AWWA, WEF (1998). \u003c/li\u003e\n\u003cli\u003eBeklioglu M (1999) A review on the control of eutrophication in deep and shallow lakes, Turkish Journal of Zoology, (23), pp. 327-336.\u003c/li\u003e\n\u003cli\u003eBooth DB, \u0026amp; Jackson CR (1997) Urbanization of aquatic systems: degradation thresholds, stormwater detection, and the limits of mitigation 1. JAWRA Journal of the American Water Resources Association, 33(5), 1077-1090.\u003c/li\u003e\n\u003cli\u003eBronmark C, Hansson LA (2018) The biology of lakes and ponds, 3rd edn. Oxford University Press, Oxford\u003c/li\u003e\n\u003cli\u003eCarlson RE, (1977) A trophic state index for lakes, Limnology, and oceanography, 22(2), pp. 361-369.\u003c/li\u003e\n\u003cli\u003eCunha DGF, do Carmo Calijuri M, \u0026amp; Lamparelli MC (2013) A trophic state index for tropical/subtropical reservoirs (TSItsr). Ecological Engineering, 60, 126-134.\u003c/li\u003e\n\u003cli\u003eDowning J A, McClain M, Twilley R, Melack J M, Elser J, Rabalais N N, \u0026amp; Howarth RW (1999) The impact of accelerating land-use change on the N-cycle of tropical aquatic ecosystems: current conditions and projected changes. New Perspectives on Nitrogen Cycling in the Temperate and Tropical Americas: Report of the International SCOPE Nitrogen Project, 109-148.\u003c/li\u003e\n\u003cli\u003eGalvez-Cloutier R, and Sanchez M (2007) Trophic status evaluation for 154 lakes in Quebec, Canada: monitoring and recommendations, The Water Quality Research Journal of Canada, 42(4), pp. 252-268.\u003c/li\u003e\n\u003cli\u003eHanazato T, Arakawa T, Sakuma M, Chang K-H, Okino T (2001) Zooplankton community in Lake Suwa: Community structure and its role in the ecosystem (in Japanese). Jpn J Limnol 62:151\u0026ndash;167\u003c/li\u003e\n\u003cli\u003eHarper DM (1992) \u003cem\u003eEutrophication of freshwaters\u003c/em\u003e (p. 327). London: Chapman \u0026amp; Hall.\u003c/li\u003e\n\u003cli\u003eHoyer MV, Frazer TK, Notestein SK, Canfield J, and Daniel E (2002) Nutrient, chlorophyll, and water clarity relationships in Florida\u0026rsquo;s nearshore coastal waters with comparisons to freshwater lakes, Canadian Journal of Fisheries and Aquatic Sciences, (59), pp. 1024\u0026ndash;1031.\u003c/li\u003e\n\u003cli\u003eHutchinson GE (1957) A treatise on limnology: Geography, physics and Chemistry, Volume 1, Wiley, New York, Chapman \u0026amp; Hall, London. pp. 108-114.\u003c/li\u003e\n\u003cli\u003eJeppesen E, S\u0026oslash;ndergaard M, \u0026amp; Liu Z (2017) Lake restoration and management in a climate change perspective: an introduction. Water, 9(2), 122.\u003c/li\u003e\n\u003cli\u003eJorgensen S, Tundisi JG, and Tundisi TM (2013) Handbook of Inland aquatic Ecosystem Management, Applied ecology and environment management, Taylor and Francis group, ISBN- 13: 978-1-4398-4526-4, pp. 1-421.\u003c/li\u003e\n\u003cli\u003eKalff J (2002) Limnology. Inland water Ecosystem, Mc Gill University, prentice Hall, pp. 1- 536.\u003c/li\u003e\n\u003cli\u003eKarmakar, S., \u0026amp; Musthafa, O. M. (2020). Lakes and reservoirs: Pollution. In Managing Water Resources and Hydrological Systems (pp. 65-80). CRC Press.\u003c/li\u003e\n\u003cli\u003eKasture, R. (2022). Critical study of role and functions of national green tribunal in protection of environment in India. Journal Homepage: http://ijmr. net. in, 10(2). \u003c/li\u003e\n\u003cli\u003eLakewatch F (2001) A Beginner\u0026rsquo;s guide to water management-Lake Morphometry. Information Circular, 104.\u003c/li\u003e\n\u003cli\u003eLambin EF, Turner BL II, Geist HJ, Agbola S, Angelsen A, Bruce JW, Coomes O, Dirzo R, Fischer G, Folke C, George PS, Homewood K, Imbernon J, Leemans R, Li X, Moran EF, Mortimore M, Ramakrishnan PS, Richards JF, Sk\u0026aring;nes H, Steffen W, Stone GD, Svedin U, Veldkamp T, Vogel C, Xu J (2001) The causes of land-use and land-cover change \u0026ndash; Moving beyond the myths Global Environmental Change, Human and Policy Dimensions, Vol. 11 (4), pp. 261-269.\u003c/li\u003e\n\u003cli\u003eLaudise JE, Laudise RA, Graedel JE, and Barns RL (1994) Water quality analysis of Twin Lakes PA, 1965-1993, A unique database, Journal of Pennsylvania Academy of Science, 68(2), 67-76 (1994).\u003c/li\u003e\n\u003cli\u003eLi J, Hansson LA, \u0026amp; Persson KM (2018) Nutrient control to prevent the occurrence of cyanobacterial blooms in a eutrophic lake in Southern Sweden, used for drinking water supply. Water, 10(7), 919.\u003c/li\u003e\n\u003cli\u003eLiu Y, Chen W, Li D, Shen Y, Li G, and Liu Y (2006) First report of aphantoxins in China\u0026mdash;waterblooms of toxigenic aphanizomenon flos-aquae in Lake Dianchi, Ecotoxicology and Environmental Safety, Elsevier, (65), pp. 84\u0026ndash;92.\u003c/li\u003e\n\u003cli\u003eOhle W (1937) Kolloid Gele als Nahrstoff regu- latoren der Gewasser, Naturwissenschaf ten, 29, pp. 471-474.\u003c/li\u003e\n\u003cli\u003ePurmalis O, Kļaviņ\u0026scaron; L, \u0026amp; Arbidans L (2019) Ecological quality of freshwater lakes and their management applications in urban territory. Proceedings of the Research for Rural Development, 1, 103-110.\u003c/li\u003e\n\u003cli\u003ePaerl HW, Xu H, Hall NS, Rossignol KL, Joyner AR, Zhu G, and Qin B (2015) Nutrient limitation dynamics examined on a multi-annual scale in Lake Taihu, China: Implications for controlling eutrophication and harmful algal blooms, Journal of Freshwater Ecology, (30), pp. 5\u0026ndash;24.\u003c/li\u003e\n\u003cli\u003ePandey J, and Verma A (2004) The influence of catchment on chemical and biological characteristics of two freshwater tropical lakes of southern Rajasthan, Journal of Environmental Biology, 25(1), pp. 81-87.\u003c/li\u003e\n\u003cli\u003ePandey J, and Yaduvanshi MS (2005) Sediment Dredging as a Restoration Tool in Shallow Tropical Lakes: Cross Analysis of Three Freshwater Lakes of Udaipur, India, Environmental Control in Biology, 43 (4), pp. 275-281.\u003c/li\u003e\n\u003cli\u003ePandey J (2011) The Influence of Atmospheric Deposition of Pollutants in Cross-Domain Causal Relationships, as for Three Freshwater Lakes in India, Lakes \u0026amp; Reservoirs: Research and Management, Blackwell Publishing Asia Pty Ltd, DOI: 10.1111/j. 1440-1770.2011. 00456.x, pp 113-121.\u003c/li\u003e\n\u003cli\u003ePandey U, and Pandey J (2013) Impact of DOC trends resulting from Changing Climatic Extremes and Atmospheric Deposition Chemistry on Periphyton Community of a Freshwater Tropical Lake of India, Biogeochemistry, Springer Science, DOI 10.1007/s 10533-012-9747-7, pp. 537-553.\u003c/li\u003e\n\u003cli\u003eParparov A, Hambright KD (2007) Composite water quality: evaluation and management feedback, Water Quality Research Journal of Canada 42 (1), pp. 18\u0026ndash;23.\u003c/li\u003e\n\u003cli\u003eParparov A, Hambright KD, Hakanson L, Ostapenia A (2006) Water quality Quantification: Basics and Implementation, Hydrobiologia 560(1) pp. 227-237. DOI: 10.1007/s10750-005-1642-y.\u003c/li\u003e\n\u003cli\u003ePearl HW, Fulton RS, Moisander PH, \u0026amp; Dyble J (2001) Harmful Freshwater Algal Blooms, With an Emphasis on Cyanobacteria, The Scientific World, 1, pp. 76-113. doi: 10.1100/tsw.2001.16\u003c/li\u003e\n\u003cli\u003eRamachandran K (2001) Assessment of contamination of Natural Resource using GIS and Remote Sensing \u0026ndash; a study of Hyderabad region, GIS India, pp. 8 \u0026ndash;13.\u003c/li\u003e\n\u003cli\u003eRhazi LP, Grillas AM, Toure and TanHam L (2001) Impact of land use in catchment and human activities on water, sediment and vegetation of Mediterranean temporary pools, Comptes rendus Acad\u0026eacute;mie Sciences, Paris (Life Science), 324, pp. 165-177.\u003c/li\u003e\n\u003cli\u003eRhodes CJ (2013) Peak phosphorus\u0026ndash;peak food? The need to close the phosphorus cycle. \u003cem\u003eScience Progress\u003c/em\u003e, \u003cem\u003e96\u003c/em\u003e(2), pp.109-152.\u003c/li\u003e\n\u003cli\u003eSahai R, and Sinha AB (1969) Investigation on Bio-ecology of Inland water of Gorakhpur (U.P.) India, Hydrobiologia, (Springer), Volume 34 Issue 3-4, Pp 433-447, Doi.org/10.1007/BF00045402.\u003c/li\u003e\n\u003cli\u003eSalman MA, Nomaan MSS, Sayed S, Saha A, \u0026amp; Rafiq MR (2021) Land use and land cover change detection by using remote sensing and gis technology in Barishal District, Bangladesh. Earth Sci Malaysia, 5(1), 33-40.\u003c/li\u003e\n\u003cli\u003eS\u0026aacute;nchez E, Colmenarejo MF, Vicente J, Rubio A, Garcia MG, Travieso L, Borja R (2007) Use of the water quality index and dissolved oxygen deficit as simple indicators of watersheds pollution, Ecological Indicators, Elsevier, 7, pp. 315\u0026ndash;328, doi: 10.1016/j.ecolind.2006.02.005.\u003c/li\u003e\n\u003cli\u003eSawyer CN (1954) Factors involved in disposal of sewage effluents to lakes, Sewage, and Industrial Wastes, 26: 317-325.\u003c/li\u003e\n\u003cli\u003eSchindler DW, Hecky R, Findlay D, Stainton M, Parker B, Paterson M, Kasian S (2008) Eutrophication of lakes cannot be controlled by reducing nitrogen input: results of a 37-year whole-ecosystem experiment, Proceedings of the National Academy of Sciences, 105(32), pp. 11254-11258.\u003c/li\u003e\n\u003cli\u003eSheergojri, I. A., Rashid, I., Aneaus, S., Rashid, I., Qureshi, A. A., \u0026amp; Rehman, I. U. (2023). Enhancing the social-ecological resilience of an urban lake for sustainable management. \u003cem\u003eEnvironment, Development and Sustainability\u003c/em\u003e, 1-26.\u003c/li\u003e\n\u003cli\u003eSingh, A and Sharma, V.N. (2018), A Stewardship of Ramgarh Lake in Gorakhpur District: Uses, Problems and Management, Transaction, Indian Institute of Geographers, Vol. 40, No. 1, pp. 33-43.\u003c/li\u003e\n\u003cli\u003eSingh, A. and Sharma, V.N. (2019), A comparative assessment of anthropogenic pressure and Trophic Levels of urban (Ramgarh lake) and rural (Chilua lake) lakes of Gorakhpur District, U.P., National Geographical Journal of India, Vol. 65 No. 4, pp. 340-349.\u003c/li\u003e\n\u003cli\u003eSingh A, \u0026amp; Sharma VN (2022) Anthropogenic impacts on lakes and measurement of Trophic Level: A comparative study of Ramgarh (Urban) and Chilua (Rural) Lakes of Gorakhpur District, UP. National Geographical Journal of India, 65(4), 340-349.\u003c/li\u003e\n\u003cli\u003eSingh A, and Sharma VN (2020) An empirical comparative study of changing utilization pattern and problems of rural and urban lakes of Gorakhpur, India, National Geographical Journal of India, DOI: 10.48008/ngji.1748.\u003c/li\u003e\n\u003cli\u003eSingh A, Sharma VN, \u0026amp; Rana NK (2024) Analysis of morphological change of lentic water bodies by using spatial vulnerability index (SVI) in Tarai region of Rapti river plains, India. Geology, Ecology, and Landscapes, 1-11.\u003c/li\u003e\n\u003cli\u003eS\u0026oslash;ndergaard M, Jeppesen E, \u0026amp; Fjord Aaser H (2000) Neomysis integer in a shallow hypertrophic brackish lake: distribution and predation by three-spined stickleback (Gasterosteus aculeatus). Hydrobiologia, 428, 151-159.\u003c/li\u003e\n\u003cli\u003eSrinath EG, and Pillai SC (1966) Phosphorus in Sewage, Polluted Waters, Sludges, and Effluents, The Quarterly Review of Biology, Vol. 41, No. 4, pp. 384-407.\u003c/li\u003e\n\u003cli\u003eTaube CM (2000) Instructions for winter lake mapping, Chapter 12 in Schneider, James, C., (ed.), (2000), Manual of fisheries survey methods II: with periodic updates, Michigan Department of Natural Resources, Fisheries Special Report 25, Ann Arbor.\u003c/li\u003e\n\u003cli\u003eWade PM (1999) The impact of human activity on the aquatic macroflora of Llangorse Lake, South Wales, Aquatic Conservation Marine Freshwater Ecosystem, pp. 441-459 (1999).\u003c/li\u003e\n\u003cli\u003eWebster CJ (1995) Urban Morphological Fingerprints, Environment, and planning, (22) pp. 279-297.\u003c/li\u003e\n\u003cli\u003eWeng Q (2001) A remote sensing\u0026ndash;GIS evaluation of urban expansion and its impact on surface temperature in the Zhujiang Delta, China, International Journal of Remote Sensing, vol. 22, no. 10, pp. 1999\u0026ndash;2014.\u003c/li\u003e\n\u003cli\u003eWetzel RG (1992) Gradient-dominated ecosystems: sources and regulatory functions of dissolved organic matter in freshwater ecosystems. \u003cem\u003eHydrobiologia\u003c/em\u003e, \u003cem\u003e229\u003c/em\u003e, 181-198.\u003c/li\u003e\n\u003cli\u003eWetzel RG (2001) Limnology, Lake, and River Ecosystems. Academic Press, New York, pp 1006, 3rd Edition - ISBN: 9780127447605.\u003c/li\u003e\n\u003cli\u003eWilliams WD (1999) Salinization: A major threat to water resources in the arid and semi-arid regions of the world, Lakes Reservation, Research Management, 4, pp. 85-91.\u003c/li\u003e\n\u003cli\u003eLi X, Sha J, \u0026amp; Wang ZL (2017) Chlorophyll-a prediction of lakes with different water quality patterns in China based on hybrid neural networks. Water, 9(7), 524.\u003c/li\u003e\n\u003cli\u003eYadav A and Pandey J (2017) Contribution of point sources and non-point sources to nutrient and carbon loads and their influence on the trophic status of the Ganga River at Varanasi, India, Environmental Monitoring Assessment, Springer, pp. 189-475, DOI 10.1007/s10661-017-6188-8.\u003c/li\u003e\n\u003cli\u003eYang J, Lv H, Liu L, Yu X, \u0026amp; Chen H (2016) Decline in water level boosts cyanobacteria dominance in subtropical reservoirs. Science of the Total Environment, 557, 445-452: doi:10.1016/j.scitotenv.2016.03.094.\u003c/li\u003e\n\u003cli\u003eYang S, Lu J, Chen X, Hou X, Wei Z, and Wu J (2023) Unraveling environmental influences on the spatial and temporal dynamics of cyanobacterial blooms in Lake Erhai during its early stage of eutrophication. Geo-Spatial Information Science, pp.1-19.\u003c/li\u003e\n\u003cli\u003eYeh AG, and Li X (2001) The measurement and monitoring of urban sprawl in a rapidly growing region using entropy, Photogrammetric Engineering \u0026amp; Remote sensing, vol. 67, No.1, pp. 88-90.\u003c/li\u003e\n\u003cli\u003eZhong S, Geng Y, Qian Y, Chen W, \u0026amp; Pan H (2019) Analyzing ecosystem services of freshwater lakes and their driving forces: the case of Erhai Lake, China. Environmental Science and Pollution Research, 26, 10219\u0026ndash;10229. doi:10.1007/s11356-019-04476-9.\u003c/li\u003e\n\u003cli\u003eZou W, Zhu G, Cai Y, Xu H, Zhu M, Gong Z, ... \u0026amp; Qin B (2020) Quantifying the dependence of cyanobacterial growth to nutrient for the eutrophication management of temperate-subtropical shallow lakes. Water Research, 177: 115806. doi:10.1016/j.watres.2020.115806.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table 4 and 5","content":"\u003cp\u003eTable 4 and 5 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-geoscience","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Geoscience](https://www.springer.com/journal/44288)","snPcode":"44288","submissionUrl":"https://submission.nature.com/new-submission/44288","title":"Discover Geoscience","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Lake morphometric, land use, shallow lake, trophic status index, ecological deterioration, stewardship","lastPublishedDoi":"10.21203/rs.3.rs-6523182/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6523182/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAquatic ecosystems regulate and play great ecological roles, for instance, provide habitats for flora and fauna, nutrient cycles, maintain stream flow, climatic control, and support livelihood security through fisheries, recreational activity etc. However, anthropogenic activities have dramatically deteriorated the aquatic ecosystem. Geospatial techniques are significant for the extraction of morphometric features of lake. An analysis of 97 years (from 1922 toposheets to Google Earth Images, 2019) of Chilua Lake in \u003cem\u003eTarai region\u003c/em\u003e, revealed deterioration scenario. The extent of Chilua Lake is reduced up 27.75% in 97 years from 1922 to 2019. As per the 500 m buffer analysis surrounds of lake Chilua, 1.3% built-up area increased around the lake within 15 years (from 2004 to 2019). For 6 to 8 months, the lake goes dry out and the water left behind in patches and engaged in various activities by the locals. Lake bed is covered by stream like storage (20%) and water is available during all seasons, water left in patches during dry season (15%), littoral plant coverage (45%), farming (11%), dry lake bed (10%), and built-up area (0.3%). Increasing built-up, farming on dry bed, dumping of solid waste and sewage entry have contributed directly pushed towards eutrophic status lake ecology at C1 (sewage entering sources) and C3 (agricultural practices) based on the BOD, BO, TP, NO\u003csub\u003e3\u003c/sub\u003e, SD, GPP, Chla, etc. This study investigates factors of lake deterioration and suggest the practices of Stewardship in the way of basin lake management techniques (BLMT) and Tripple-P model.\u003c/p\u003e","manuscriptTitle":"Using Geographic Information Systems (GIS) to Assess Lake Morphometry, Siltation-Induced Ecological Deterioration, and Land Use/ land cover practices on the Dry Bed of Chilua Lake, Tarai Region, India","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-11 06:07:06","doi":"10.21203/rs.3.rs-6523182/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-18T20:31:42+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-29T03:07:46+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"306160154986357596783381093712824217736","date":"2025-06-10T10:12:42+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-09T04:42:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"33682421196663097511637090365734620111","date":"2025-06-09T02:18:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"280033078029677910785887670181729753751","date":"2025-06-09T02:02:40+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-08T22:37:14+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-16T04:22:58+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-16T04:22:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Geoscience","date":"2025-04-24T18:35:44+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-geoscience","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Geoscience](https://www.springer.com/journal/44288)","snPcode":"44288","submissionUrl":"https://submission.nature.com/new-submission/44288","title":"Discover Geoscience","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"39258233-baa2-4905-ac19-9d4a2d003e05","owner":[],"postedDate":"June 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-10-23T05:08:16+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-11 06:07:06","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6523182","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6523182","identity":"rs-6523182","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}