Assessing the impacts of climate change on the vulnerability of coastal aquifers to the seawater intrusion

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Climate change effects, such as the sea-level rise and rainfall change are the climatic factors affecting the saltwater intrusion into groundwater. This study examines the vulnerability of the Abdan-Lamidan coastal aquifer to the intrusion of Persian Gulf saline waters under different hydrological conditions. First, the SIMCLIM model was used to calculate the regional sea-level rise of the Gulf under 24 future AOGCMs projections. The results showed that the increase in water level under the ensemble of AOGCM models and two RCP2.6 and RCP8.5 scenarios is 6.7 and 7.8 cm in 2050 compared to 2013. Then, the GALDIT vulnerability index was used to assess the vulnerability of the aquifer under the current condition and future scenarios. The results showed that parts of the aquifer that are currently at lower levels would be more vulnerable to sea-level rise in the future periods. Aquifer vulnerability Climate change Coastal aquifer GALDIT index Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Climate change is causing significant environmental damage, including rising temperatures, changing rainfall and rising sea levels, destroying natural habitats and biodiversity [ 1 ]. Groundwater in most coastal areas, as the most important source of freshwater, is affected by seawater intrusion [ 2 ]. The most important environmental hazard to coastal aquifers is the seawater intrusion into coastal aquifers [ 3 , 4 ]. The saltwater intrusion into the coastal aquifer is a natural phenomenon that occurs due to the difference in density between seawater and groundwater [ 2 , 5 ]. The salinity condition of coastal aquifers will be worse by increasing demand for freshwater in the coastal areas (water extraction from the aquifer), and predictions of rising sea levels of 0.1 to 2 m by the end of the year 2100 [ 2 , 6 – 8 ]. The climate change impacts, such as rising sea levels and rainfall changes which lead to changes in the aquifer recharge rate, are the climatic factors that affect saltwater intrusion. Therefore, this issue has investigated by previous studies [ 9 – 16 ]. As the sea level rise in the near future is a serious threat and controversial issue for coastal [ 17 , 18 ], therefore the estimate of sea level rise in the future periods is necessary. Permanent and temporary flooding, erosion of coastlines, destructive storms and the seawater intrusion into freshwater aquifers are the physical effects of sea level rise [ 19 ]. Various studies were investigated the extent of sea level changes and its effects on coastal ecosystems. Sea level increase in the future which results in various coastal damages was approved by these studies [ 20 – 25 , 2 , 16 ]. Sea-level changes are affected by two significant factors: the change in volume caused by changes in water density and mass change due to water exchanges between the atmosphere and the earth through precipitation, evaporation, river runoff and ice melting [ 19 , 26 ]. According to the IPCC-AR5 reports, in the 21st century, global mean sea levels will increase as a result of the thermal expansion of the oceans and the melting of polar ice sheets and glaciers. Based on the global sea level rise scenarios, sea level will rise by 26 to 82 centimeters over the next 100 years [ 27 , 28 ]. On the other hand, studies have shown that regional sea level changes are different from global sea level changes [ 28 ]. Therefore, the application of global mean sea level rises in coastal aquifers vulnerability calculation under seawater influences will result in uncertainties. Therefore, some researches have been conducted to calculate the precise level of regional sea level rise [ 20 , 28 ]. In order to estimate the local sea level changes, some researchers have defined the hypothetical scenarios of water level increases [ 21 – 24 , 29 , 13 , 30 ] and others used the results of AOGCM simulations [ 20 , 14 , 31 , 25 ]. Aquifer vulnerability is a relative, non-dimensional, and unmeasurable property and depends on the characteristics of the aquifer, its geological environment, and hydrogeology [ 32 ]. The vulnerability of the aquifer is defined as the ease and possibility of infiltration and dispersion of the pollution from the surface to the aquifer. Several methods have been proposed to determine vulnerability: PI [ 33 ], DRASTIC [ 34 , 35 ], SINTACS [ 36 , 14 ], EPIK [ 37 ], IRISH [ 38 ], AVI [ 39 , 14 ], GOD [ 40 ], GALDIT [ 41 – 43 ] and VESPA [ 44 , 45 ]. Each of these methods is achieved regarding specific conditions and different data. The vulnerability of seawater intrusion in coastal aquifers for the first time evaluated by Chachadi and Lobo-Ferreira to assess the level of aquifer contamination and the seawater intrusion into coastal aquifers (GALDIT) [ 41 ]. The GALDIT model is based on the development of the DRASTIC model which is introduced by Aller in 1987. The DRASTIC model uses seven hydrogeological parameters in order to calculate the vulnerability of groundwater under seawater infiltration in the regional scale [ 46 , 47 ]. However, the GALDIT model uses six hydrogeological parameters to calculate the vulnerability of seawater intrusion in larger scales [ 48 ]. Although models such as DRASTIC can be used to estimate the vulnerability of aquifers, the GALDIT model examines the vulnerability of aquifer under seawater intrusion influences in wider scales, especially in coastal areas [ 48 ]. The GALDIT can assess the degree of vulnerability to seawater intrusion in different conditions, such as sea level changes, changes in recharging rates influenced by climate change and groundwater discharge to the sea. The model uses a combination of various hydrological components in order to assess the vulnerability of aquifers under different conditions [ 16 ]. The widespread application of the groundwater vulnerability index (GALDIT) confirms the ability of the model to estimate vulnerability changes more accurately [ 9 , 22 , 3 , 14 , 49 – 55 ]. Application of the global mean sea level rise values in coastal vulnerability calculations will not provide accurate results. Therefore, in this study, the SIMCLIM model [ 56 ], was used to calculate the sea level rise in the Persian Gulf region. Moreover, seawater intrusion into coastal freshwater aquifers which is influenced by the increase of Persian Gulf level and groundwater discharge is a serious threat to the coastal groundwater resources in the study area. Therefore, in this study, the vulnerability of the coastal aquifers of Bushehr province (located in southern Iran) has been evaluated by considering the seawater intrusion due to climate change using GALDIT model. 2. Materials and Methods 2.1. Study Area The study area of ​​this research is located in the Bushehr province in southern Iran, along with the northern coast of the Persian Gulf. The aquifer area of ​​the study is at an east-east distance of 52° 8 '10 ” East to 51° 42'50 ” and a latitude of 27° 46' 10 " to 28° 6' 20 " (Fig. 1 a, b,c). Abdan Lamidan aquifer with a total area of ​​285.5 km 2 has 52 observation wells. Total 16 wells data were used for vulnerability assessment regarding hydraulic conductivity. The hydraulic conductivity experiment of three wells in 2002 and 13 other wells in 2007 was carried out by Step-Drawdown Pumping Test methods, respectively. In this research, groundwater level information of 46 wells of the year 2010–2011 has been used. In order to analyze the salinity of aquifer under the influence of seawater intrusion, carbonate, bicarbonate and chlorine data of 111 operational and observational wells of the aquifer (deep and semi-deep) for the year 2013 were used. The aquifer thickness data was for the period 2010–2011. The thickness of the aquifer is increased from 100 to 145 meters from north to south. Based on the report of the National Water Resources Management Company (2011), annual Abdan-Lamidan aquifer groundwater discharge was 35.57 million cubic meters. The results of aquifer budget assessment report in this area indicate that the total output of the aquifer in the past few years has been much higher than the inputs to the aquifer. As a result, the groundwater level is constantly decreasing in such a way that in the southern parts of Abdan-Lamidan aquifer, the groundwater level is 10 meters below the sea level. Figure 1 The location of the study area in the south of Iran(a), the location of the Abdan-Lamidan aquifer in the Bushehr province, relative to the Persian Gulf (b), the position of the observation wells in the Abedan-Lamidan aquifer area to the Persian Gulf coast (c) 2.2. Simulation of regional sea level changes under climate change The vulnerability assessment of the of the Abdan-Lamidan coastal aquifer to the intrusion of Persian Gulf seawater in the future periods requires simulation and estimation of the regional sea level rise. In this research, the SIMCLIM model was used to investigate the level of changes in the Gulf water regime under climate change impacts. SIMCLIM is a tool designed to facilitate the assessment of climate change impacts. SIMCLIM uses the latest CMIP5 climatic models (CLIMsystems 2013). In the SIMCLIM model, seawater level changes over time are estimated based on the increase in air temperature, which leads to thermal expansion and increased polar ice melting [ 20 , 57 ]. The global and regional spatial resolution of the model is about 2.5°×2.5° and 0.1°, respectively [ 56 ]. SIMCLIM was run for 24 AOGCMs presented in Table 1 under two climate change scenario RCP 2.6 and RCP 8.5 from 1955 to 2050. Table 1 Characteristics of the 24 AOGCM models for the fifth Assessment report (AR5) used in this study. Model Research center Scenario Spatial resolution for ocean variable (longitude*latitude) Spatial resolution for atmospheric variable (longitude*latitude) BCC-CSM1-1 BCC (China) RCP2.6 3.6° × 2.32° 1.28°×0.64 ° BCC-CSM1-1-m BCC (China) RCP2.6، RCP4.5، RCP6.0، RCP8.5 3.6° × 2.32° 3.2°×1.6° CanESM2 CCCma (Canada) RCP2.6,RCP4.5,RCP8.5 2.56°×1.92° 1.28°×0.64° CCSM4 NCAR(USA) RCP2.6، RCP4.5، RCP6.0، RCP8.5 3.2°×3.84° 2.88°×1.92° CMCC-CM CMCC (Italy) RCP4.5, RCP8.5 1.82°×1.49° 4.8°×2.4° CMCC-CMS CMCC (Italy) RCP4.5, RCP8.5 1.82°×1.49° 1.92°×0.96° CNRM-CM5 CNRM-CERFACS(France) RCP2.6, RCP4.5, RCP8.5 3.62°×2.92° 2.56°×1.28° CSIRO-Mk3-6-0 ABM(Australia) RCP2.6، RCP4.5، RCP6.0، RCP8.5 1.92°×1.89° 1.92°×0.96° GFDL-CM3 NOAA GFDL (USA) RCP2.6، RCP4.5، RCP6.0، RCP8.5 3.6°×2° 1.44°×0.9° GFDL-ESM2G NOAA GFDL (USA) RCP2.6، RCP4.5، RCP6.0، RCP8.5 3.6°×2.1° 1.44°×0.9° GFDL-ESM2M NOAA GFDL (USA) RCP2.6، RCP4.5، RCP6.0، RCP8.5 3.6°×2° 1.44°×0.9° GISS-E2-R NASA/GISS (USA) RCP2.6، RCP4.5، RCP6.0، RCP8.5 2.88°×1.8° 1.44°×0.9° GISS-E2-R-CC NASA/GISS (USA)) RCP2.6، RCP4.5، RCP6.0، RCP8.5 2.88°×1.8° 1.44°×0.9° HadGEM2-CC MOHC (UK) RCP4.5, RCP8.5 3.6°×2.16° 1.92°×1.45° HadGEM2-ES INPE (UK) RCP2.6, RCP4.5, RCP8.5 3.6°×2.16° 1.92°×1.45° INMCM4 INM (Russia) RCP4.5, RCP8.5 3.6°×3.4° 1.8°×1.2° MIROC5 MIROC (Japan) RCP2.6، RCP4.5، RCP6.0، RCP8.5 2.56°×2.24° 2.56°×1.28° MIROC-ESM MIROC (Japan) RCP2.6، RCP4.5، RCP6.0، RCP8.5 2.56°×1.92° 1.28°×0.64° MIROC-ESM-CHEM MIROC (Japan) RCP2.6، RCP4.5، RCP6.0، RCP8.5 2.56°×1.92° 1.28°×0.64° MPI-ESM-LR MPI-M (Germany) RCP2.6, RCP4.5, RCP8.5 2.56°×2.2° 1.92°×0.96° MPI-ESM-MR MPI-M (Norway) RCP2.6, RCP4.5, RCP8.5 8.02°×4.04° 1.92°×0.96° MRI-CGCM3 MRI (Japan) RCP2.6، RCP4.5، RCP6.0، RCP8.5 3.6°×3.68° 3.2°×1.6° NorESM1-M NCC (Norway) RCP2.6، RCP4.5، RCP6.0، RCP8.5 3.2°×3.84° 1.44°×0.96° NorESM1-ME NCC (Norway) RCP2.6، RCP4.5، RCP6.0، RCP8.5 3.2°×3.84° 1.44°×0.96° *RCP: Representative concentration pathways are four greenhouse gas concentration (not emissions) trajectories adopted by the IPCC for its fifth assessment Report (AR5) in 2013 [ 59 ] The RCP 2.6 is representative of scenarios that lead to very low greenhouse gas concentration levels. It is a “peak-and-decline” scenario; its radiative forcing level first reaches a value of 3.1 W m − 2 by mid-century and returns to 2.6 W m − 2 by 2100. To reach such radiative forcing levels, greenhouse gas emissions are reduced substantially over time. The RCP 8.5 is characterized by increasing greenhouse gas emissions over time that lead to high greenhouse gas concentration levels. It is a “rising” scenario; its radiative forcing level continuously rises to 8.5 W m − 2 by 2100 [28; 58–60]. Table 1 Characteristics of the 24 AOGCM models for the fifth Assessment report (AR5) used in this study. 2.3. Coastal aquifer vulnerability assessment The evaluation of the aquifer's vulnerability to the saltwater intrusion was carried out using a GALDIT approach. This index, is based on the nature of the aquifer (G), the hydraulic conductivity (A), the level of groundwater above the sea (L), the distance of the aquifer from the sea (D), the magnitude and extent of saltwater intrusion into the aquifer, (I) and the aquifer thickness (T) [41; 54]. These parameters are the essential components of seawater intrusion to coastal aquifers [ 42 ]. Type of aquifer (G): According to the layout of the geological layers, there are different types of aquifers (unconfined, confined or under pressure, leaky aquifer, and perched). The expansion of the saltwater intrusion depends on natural properties and the type of aquifer [ 61 – 63 ]. Therefore, in unconfined aquifers, the lowest layer has a significant effect on the interference of seawater with fresh water. On the other hand, confined aquifers are more sensitive due to larger loss cone during the pumping time. Hydraulic conductivity (A): The magnitude of salinity intrusion in the aquifer is influenced by the hydraulic conductivity of the aquifer formation. Larger hydraulic conductivity causes more significant seawater intrusion to the coastal aquifer [ 42 ]. The hydraulic conductivity of the aquifer is estimated based on the flow velocity in the aquifer layers. Hydraulic conductivity is the ability of the aquifer to transfer water, which is the result of effective porosity in sediments and aquifer constituents. The high hydraulic conductivity increases the surface of the drop cone during pumping. In this study, first, transmittance coefficient was estimated using the results of geophysical experiments, and then the hydraulic conductivity was calculated by dividing the raster layer of the transmittance coefficient into the aquifer layer thickness in the region. The height of the groundwater level above sea level (L): the ratio of groundwater table to mean sea level is one of the most important parameters in assessing the susceptibility to saltwater intrusion. This parameter is dynamic and primarily related to the piezometric conditions of the coastal aquifer due to its spatial variability. The lower the water table in comparison to the sea level, there is more vulnerability to increase the water level, as well as contamination through the saltwater intrusion into aquifers. Distance from the seashore (D): The closer parts of the aquifer to the coast experience highest impact of seawater intrusion. The aquifer classification is considered based on the aquifer distance from the seashore, according to the classification presented in Table 2 . Different aquifer classes are weighted according to their distance from the coast, with numbers 2.5, 5, 7.5 and 10. The effect of seawater and waves advancement (as a wave motion) toward the coast has a range of decreasing effect. When the distance from the coast increases, the vulnerability of the aquifer decreases. In this study, classification and weighting were done by ArcGIS software. Table 2 Parameters of GALDIT method Indicator Importance rating 2.5 5 7.5 10 Very low Low Medium High 1 2 3 4 Weight Groundwater occurrence/aquifer type 1 Bounded aquifer (Recharge and/or impervious boundary aligned parallel to the coast) Leaky confined Aquifer Unconfined aquifer Confined aquifer Aquifer hydraulic conductivity (m day − 1 ) 3 < 5 5–10 10–40 40 2 1.5-2 1-1.5 1> Distance from shore/ high tide (m) 4 > 1000 750–1000 500–750 < 500 Impact status of existing seawater intrusion 1 2 Aquifer thickness (Saturated) (m) 2 10 [ 41 , 48 ] Impact of the existing status of seawater intrusion (I): The effect of saltwater intrusion is measured based on the concentration of chlorine, carbonate and bicarbonate anions (Eq. 1 ) [ 41 ]. The data are obtained from observational wells and local exploration wells. Due to the hydraulic gradient balance distribution between seawater and freshwater, the chlorine concentration in observation wells increases relative to carbonate and bicarbonate concentrations. Selection of the mentioned anions, especially chlorine, has been proposed based on the fact that this parameter is predominant in groundwater in coastal areas. (Revelle 1941) recommended the ratio of Cl / [ HCO 3 + CO 3 ] as a criterion to identify the extent of seawater intrusion into the coastal aquifers. $$\:I=\:\frac{{CL}^{-}}{{CO}_{3}^{2-}+\:{HCO}_{3}^{-}}$$ 1 Aquifer thickness (T): The aquifer thickness or the aquifer saturation zone is between the water table and the impermeable layer. The difference between the water table and the bedrock layer is considered as the thickness of the aquifer. The thickness of the aquifer varies in spatial scales; larger aquifers are more vulnerable [ 41 , 64 , 54 ]. Aquifers with a thickness of more than 10 meters are entirely exposed to severe seawater infiltration vulnerability. After GALDIT index parameter estimation, the model parameters should be weighed. Each of the GALDIT index parameters has a weight which is indicated by W in Eq. 2 . The details of the GALDIT index parameters and the weight of each parameter, regarding its importance, in the probability of occurrence of the saltwater infiltration, are given in Table 2 [ 41 ]. The weighting of the parameters is carried out depending on the importance of each of the parameters (based on the assigned weight). The GALDIT index after estimating the maps for each of its components is estimated using the weight of 6 parameters (Eq. 2 ). $$\:GALDIT=\:\frac{\sum\:_{i=1}^{6}{W}_{i}{\times\:R}_{i}}{\sum\:_{i=1}^{6}{W}_{i}}$$ 2 Table 2 Parameters of GALDIT method 2.4. Climate change impact on coastal aquifer vulnerability As the sea level rises due to climate change, the coastline advances to coastal aquifers and occupies part of the aquifer. Among the different parameters of the GALDIT index, it is expected that two parameters of the groundwater table above seawater level and distance from the seashore (L and D) will be varied due to changes in the water balance in the future periods. In this study, the hydraulic conductivity, type of aquifer, the thickness of the aquifer’s saturation zone and the magnitude of infiltrated saltwater parameters are assumed to be constant in the aquifer in the future in comparison with the current condition. After calculating the sea level changes under climate change, the flooding of the aquifer was calculated in 2050 (parameter D). To calculate coastal flooding, seawater level changes based on average of AOGCM models were considered under averages of RCP2.6 and RCP8.5 scenarios in 2050. Because of the slight difference in the amount of sea level rise in 2050 under different RCP scenarios, the mean values ​​of RCP2.6 and RCP8.5 (as the best-worst-case scenario) in the year 2050 was considered. After calculating the coastal flooding due to changes in sea level and coastline advance relative to Abdan-Lamidan aquifer boundary, the aquifer classification was carried out based on aquifer distance from the coastline using the buffer order in ArcGIS software. Additionally, the change in the parameter of aquifer distance from the coast (D) was calculated in 2050 relative to the baseline period. The height of the groundwater level above sea level (L) is another parameter of the GALDIT index which will vary with sea level changes. This parameter may be affected by various factors such as an increase in seawater levels under climate change and drop in aquifer water levels due to excess capacity extractions or other factors. In this research, the impact of climate change on sea level rise and natural water loss of aquifer due to extraction has been investigated. Climate change projections show that water level increases under different RCP scenarios in the future. The changes in water level are not significantly different under different scenarios in 2050. Therefore, the sea level rise is calculated based on the changes in the water level under average RCP2.6 and RCP8.5 scenarios. The level of aquifer loss in the future periods is calculated based on aquifer water level changes during the past periods. To obtain (L), the water level values ​​in observation wells under the combined effects of climate change and water loss during the water extraction from Abdan-Lamidan aquifer was considered. This was done through the representative hydrograph of the aquifer over a period of 12 years from 2004 to 2015, and the calculation of the annual water level loss rate for the aquifer. Additionally, it is assumed that the aquifer's current condition is continued regarding groundwater balance. It is assumed that the calculated annual water loss rate in the future will continue at the same rate. Therefore, the difference in water level in observation wells is calculated relative to the sea level rise under climate change impact as well as the level of water loss in the aquifer in 2050. 3. Results 3.1. Aquifer vulnerability under current condition scenario Figure 2 shows the status of the various parameters of the GALDIT index in the recent scenario. Figure 2 a shows the vulnerability of the Abdan-Lamidan aquifer based on the aquifer type (G). Since the Abdan-Lamidan aquifer is unconfined, according to Table (2), the aquifer is placed in the same class regarding the parameter (G). As shown in (Fig. 2 a), the aquifer is in the middle-class vulnerability. The vulnerability of the Abdan-Lamidan aquifer based on the hydraulic conductivity parameter (A) is shown in (Fig. 2 b). According to the hydraulic conductivity of the aquifer, which varies from 2.67 to 50 m day − 1 , the aquifer is classified into four classes regarding vulnerability according to Table 2 . According to Table 2 , about 41.3, 34.67, 233.21, and 13.12 square kilometers of the area of the aquifer has very low, low, moderate and high vulnerability, respectively. On the other hand, about 1.2%, 12.19%, 82% and 4.6% of the aquifer area have very low, low, moderate and high levels of vulnerability. The results showed that the hydraulic conductivity values ​​of the aquifer in the coastal areas are less than the values ​​in the northern region. Therefore, the aquifer's ability to transfer salinity in parts near the sea is lower than other parts of the aquifer. Figure 2 c represents the vulnerability of the Abdan-Lamidan aquifer based on the Height of groundwater level above sea level (L). Groundwater tables above sea level of Abdan-Lamidan aquifer are located in the observation wells at a distance of -0.52 to 23.30 meters. According to the results, the water level in the observation wells increases compared to the mean sea level with the distance from the coast. Based on available water levels data, the groundwater table above the sea level is classified into four classes (Table 2 ). According to L values, 66.71, 0.62, 0.62, 32.05% of the aquifer has very low, low, moderate and high vulnerability, respectively. It is expected that the effect of this parameter (L) on the output of the GALDIT index is significant due to the high weight of this parameter in calculating the final vulnerability index. In (Fig. 2 d) the vulnerability of the Abdan-Lamidan aquifer is shown based on the distance from the seashore parameter (D). According to the table (2), the aquifer is classified into four classes regarding the parameter of distance from the aquifer. The Abdan-Lamidan aquifer southern parts are located on the tangent to the coastline and northern parts are in distance of more than 10 kilometers from the coastline. The large part of the aquifer is exposed to very low vulnerability due to the position of the aquifer relative to the coastline. This parameter has a significant effect on final vulnerability and GALDIT index calculation of the aquifer. According to D values, about 275.27, 3.55, 3.23 and 4.85 square kilometers of aquifer area has very low, low, moderate and high vulnerability. In other words, about 95.94%, 1.24%, 1.13% and 1.69% of the aquifer has very low, low, moderate and high vulnerability, respectively. The vulnerability of the Abdan-Lamidan aquifer based on the current state of the aquifer to seawater infiltration parameter (I) is presented in (Fig. 2 e). Based on the amount of carbonate, bicarbonate, and chlorine recorded in the aquifer utilization and observation wells, according to the classification of Table (2), the entire aquifer was classified into one class. The values of this parameter in the aquifer vary from a minimum value of 1.875 to 175. According to the classification guide, the aquifer is severely vulnerable. Figure 6 f shows the vulnerability of the Abdan-Lamidan aquifer based on the thickness of the aquifer saturation zone parameter (T). The saturation zone of the aquifer is more than 10 meters thick. Thus, according to the table (2), the northern parts to the coastal areas were divided into one class. The entire Abdan-Lamidan aquifer is subject to severe vulnerability with regards to the thickness of the saturation zone. Figure 2 Abdan-Lamidan vulnerability under six vulnerability indicators in the current condition, Aquifer Type(a), Hydraulic conductivity(b), Height of groundwater level above sea level(c), Distance from the shore(d), Impact of existing of status of seawater intrusion(e), Thickness of aquifer(f) After estimating and weighing the parameters of the GALDIT index, the index was calculated based on the importance of each parameter. The vulnerability results based on the GALDIT index are presented in (Fig. 3 ). As shown in (Fig. 3 ), in areas close to the coast, areas with lower water levels in the aquifer, and areas with a high hydraulic conductivity have a higher degree of vulnerability than other parts. Based on this index, 168.59, 92.13 and 11.63 km 2 of the aquifer are under low, medium and high vulnerability. In other words, about 61.89%, 33.82% and 4.27% of the aquifer have a low, moderate and severe vulnerability. Figure 3 Abdan-Lamidan vulnerability based on GALDIT index in the current condition scenario 3.2. Aquifer vulnerability under climate change impact Figure 4 shows the increasing trend in seawater level in the study area under the impacts of an ensemble of AOGCM models in the future. Results show that water levels will increase under the different RCP scenarios. The regional sea level changes under different RCP scenarios in 2050 is not significantly different in the study area. Based on the average scenario of RCP2.6 and RCP8.5, the water level will increase by about 25.5 cm in 2050 compared to 2013. As a result of sea level rise, coastline advancement occurs relative to the aquifer boundary. The sea level rise in 2050 compared to 2013 will lead to changes in the groundwater table above sea level parameter (L) and more flooding of the Abdan-Lamidan aquifer. Figure 4 Sea level changes of Persian Gulf under different RCP scenarios until 2050 Based on the calculated flooding due to the increase in seawater levels under climate change in 2050, approximately 17.20 km 2 of coastal zone will be flooded. This amount of flooding does not only cover about 10 km along the coast of the Persian Gulf region (the least sloping areas) but also covers about 0.7 km 2 of the Abdan-Lamidan area (Fig. 6 b). Therefore, the coastal distance from the aquifer boundary parameter (D) also varies under flooding conditions. Based on this parameter, 86.85, 2.7, 2.88 and 7.81% of the aquifer are under very low, low, medium and high vulnerability, respectively. Thus, the percentage of areas of the aquifer that are more vulnerable in the base period increases. Other parts of the aquifer, which are less vulnerable are reduced and classified in more vulnerable class. As a result of sea level rise, about 9.36 percent of the area of the aquifer, which was previously in a very low vulnerable class, is subjected to more vulnerability. In other words, the area of ​​the aquifer, which is in a very low vulnerable class, is reduced by 9.36 percent. Therefore, the percentage of aquifer area in low, moderate and severe vulnerability classes increased by 1.46%, 1.75%, and 6.12%, respectively. In order to calculate the parameter L of the GALDIT index under climate change, the annual water level loss rate was first calculated using the representative hydrograph of the aquifer over a period of 12 years, from 2004 to 2015. The amount of water level loss over the last 12 years is about 14 cm y − 1 (Fig. 5 ). Assuming that the current aquifer condition regarding water budget continues in the future, it is expected that in 2050 the aquifer's water level would have dropped by about 18.5 meters compared to 2013. By applying the effects of water level loss of the aquifer and sea level rise (Fig. 6 a), in 2050, about 56.18, 1.68, 0.85 and 41.19% of the aquifer were under very low, low, medium and severe vulnerability. Thus, the percentage of areas of the aquifer that are more vulnerable in the base period increases. Other parts of the aquifer, which are less vulnerable are reduced and classified in more vulnerable class. As a result of water level rise, about 10.53 percent of the area of the aquifer, which was previously in a very low vulnerable class, is subjected to more vulnerability. Therefore, the percentage of aquifer area in low, moderate and severe vulnerability classes increased by 1.06%, 0.23% and 9.14%, respectively. Figure 5 Water level loss trend in the study area in 2004–2015 Figure 6 Study area vulnerability under Height of groundwater level above sea level (a), Distance from the shore(b) in 2050 By running the GALDIT model for 2050 and taking into account the effects of the parameters of D and L under climate change about 51.14% (139.16 km 2 ), 34.66% (94.32 km 2 ) and 14.15% (38.5 km 2 ) of the area of the aquifer would be under low, moderate and severe vulnerability (Fig. 7 ). Figure 7 GALDIT model results under sea level rise and water level loss scenarios in 2050 The comparison of the application of GALDIT vulnerability index in the current condition scenario and the future scenario shows that due to sea level rise, parts of the aquifer which are low vulnerable in the present time will be more vulnerable in the future. In fact, with sea level rise in the future, more extensive parts of the aquifer will be severely vulnerable. Therefore, the area of the aquifer which will be severely vulnerable will be 3.3 times relative to the current condition scenario (Table 3 , Fig. 3 , Fig. 7 ). Table 3 Vulnerability variations of the Abdan-Lamidan aquifer under current and future condition scenarios Vulnerable areas (%) Class Low vulnerability Moderate vulnerability High vulnerability 2 3 4 Period (year) 2013 61.89 33.82 4.27 2050 51.14 34.66 14.15 Table 3 Vulnerability variations of the Abdan-Lamidan aquifer under current and future condition scenarios 4. Discussions Coastal aquifers are one of the most important sources of freshwater water in most of the coastal areas of the planet. These aquifers are threatened by the seawater intrusion due to sea level rise under climate change in the future. In this research, the GALDIT index is used to investigate climate change impacts on the vulnerability of Abdan-Lamidan coastal aquifer under two scenarios (current condition (2013) and the future scenario (2050)). The GALDIT model was run based on the values ​​of six variables of hydraulic conductivity, type of aquifer, the thickness of the aquifer saturation zone, Impact of the existing status of seawater intrusion, Height of groundwater level above sea level and the aquifer distance from the shore in the present condition (2013). According to the results of the GALDIT model, under the current condition scenario, about 61.89%, 33.82% and 4.27% of the aquifer are a low, moderate and severe vulnerability, respectively. In order to investigate the effects of climate change on the vulnerability of the study area in 2050, it was assumed that the hydraulic conductivity, type of aquifer, the thickness of the aquifer saturation zone and the impact of existing status of seawater intrusion parameters in 2050 were constant relative to the existing conditions. However only two parameters of the height of the groundwater level above sea level and the aquifer distance from the seashore were varied. In this regard, the height of groundwater level above sea level parameter was simulated under the impacts of sea level rise and the loss of water level in aquifers due to factors such as climate change and overcapacity extraction in 2050. Climate change impact results on water level changes revealed that the water level would increase about 25.5 cm in 2050 in the region compared to 2013 based on the average of the AOGCM models under the two scenarios RCP2.6 and RCP8.5. On the other hand, by assuming that the current aquifer conditions will continue in the future, the water level will fall by 14 cm annually and about 18.5 m in 2013–2050. Other researchers, for instance, Santha Sophiya and Syed (2013), also indicated an increase in the vulnerability of coastal aquifers as a result of seawater intrusion, due to the increase in water levels in 2050. In addition, according to Ebert et al. (2016) research on the effect of water level increase under climate change in future periods on the percentage of wells located in the coastal zone and affected by seawater intrusion, showed that 2 meters increase in the Baltic Sea water level about 99 km 2 (about 3 percent) of the coast of the Gotland Island in Sweden will flood. This flooding will cause salinity in 231 wells out of 7354 wells. By running the GALDIT model based on the changes in two parameters of the groundwater table above the sea and the distance of the aquifer from seashore approximately 14.15%, 34.66% and 51.14% of the aquifer will be under low, moderate and severe vulnerability in 2050. The vulnerability comparisons obtained from the GALDIT vulnerability index in the current condition to the future scenarios indicate that parts of the aquifer that are currently low vulnerable will be more vulnerable in the future. In fact, with sea level rise in the future, more areas of the aquifer will be severely vulnerable. Therefore, the area of the aquifer which will be severely vulnerable will be 3.3 times relative to the current condition scenario. GALDIT index results show that 14.15% of the aquifer is under severe vulnerability in 2050, while only 4.27% of the aquifer was severely vulnerable in 2013. Recinos (2015(was shown that based on the GALDIT index results in 1992 and 2004, the aquifer's vulnerability increased during the 13-year period. The vulnerability was 60% of the aquifer in 2004, while only 45% of the aquifer was severely vulnerable and other areas were moderate in 1992. Based on the projected conditions in future periods, proper management of water harvesting from the aquifer to maintain a balance between salt and fresh water levels and the implementation of artificial feeding plans in parts of the aquifer will improve the status of the aquifer. Considering the more significant impact of water discharge relative to the effect of climate change, in changes of groundwater table above sea level parameter, providing effective solutions to improve water management in coastal areas, have a more significant impact on environmental risk reduction of seawater intrusion into freshwater. Declarations Acknowledgment The authors thank the Ministry of Energy (MOE) for collaborating on providing the necessary information (information on groundwater parameters) in conducting research. Additionally, authors thank the SIMCLIM 2013 software development team for providing the software and sea level data set for future forecasts of sea level (the Persian Gulf and Oman). Competing Interests statement: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding statement: We have no conflict of interest to declare. “No funding was obtained for this study”. Declarations statement: All authors have read, understood, and have complied as applicable with the statement on "Ethical responsibilities of Authors" as found in the Instructions for Authors. The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request. Data availability statements: The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request. References Roohi M, Faeli M, Jamshidi F, Ghasroddashti AP. Snow parameters modeling using remote sensing techniques and HEC-HMS hydrological modeling—case study: Kan Basin. Environ Monit Assess. 2023;195(6):684. Kuan WK, Jin G, Xin P, Robinson C, Gibbes B, Li L. Tidal influence on seawater intrusion in unconfined coastal aquifers. Water Resour Res. 2012;48(2). doi:10.1029/2011WR010678. 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07:41:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4771890/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4771890/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":63041636,"identity":"bf5f3871-f418-4d0b-b4f7-1d2be4fc310d","added_by":"auto","created_at":"2024-08-22 11:38:59","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1713282,"visible":true,"origin":"","legend":"\u003cp\u003eThe location of the study area in the south of Iran(a), the location of the Abdan-Lamidan aquifer in the Bushehr province, relative to the Persian Gulf (b), the position of the observation wells in the Abedan-Lamidan aquifer area to the Persian Gulf coast (c)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4771890/v1/185601f91334de407a5048cb.png"},{"id":63041632,"identity":"282df6ae-fa45-418d-89a2-54a14afa2c78","added_by":"auto","created_at":"2024-08-22 11:38:59","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":498993,"visible":true,"origin":"","legend":"\u003cp\u003eAbdan-Lamidan vulnerability under six vulnerability indicators in the current condition, Aquifer Type(a), Hydraulic conductivity(b), Height of groundwaterlevel above sea level(c), Distance from the shore(d), Impact of existing of status of seawater intrusion(e), Thickness of aquifer(f)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4771890/v1/0602c446a86b48228dd73236.png"},{"id":63041638,"identity":"d070bace-924b-457c-88f0-2b7ac46d53a6","added_by":"auto","created_at":"2024-08-22 11:38:59","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":100031,"visible":true,"origin":"","legend":"\u003cp\u003eAbdan-Lamidan vulnerability based on GALDIT index in the current condition scenario\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4771890/v1/b8d72f6631fe9a44cb5399a2.png"},{"id":63041633,"identity":"0feb80ca-34e1-4cba-ad34-3ffa382160f9","added_by":"auto","created_at":"2024-08-22 11:38:59","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":90507,"visible":true,"origin":"","legend":"\u003cp\u003eSea level changes of Persian Gulf under different RCP scenarios until 2050\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4771890/v1/05df974a7c7f13373c51c556.png"},{"id":63042434,"identity":"073171c1-84ae-4500-9994-84dd0a635b48","added_by":"auto","created_at":"2024-08-22 11:46:59","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":53371,"visible":true,"origin":"","legend":"\u003cp\u003eWater level loss trend in the study area in 2004-2015\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4771890/v1/0a72d479eb02e3f6fd31c937.png"},{"id":63043390,"identity":"13d705ad-2713-4085-a786-226f7ffb1501","added_by":"auto","created_at":"2024-08-22 12:02:59","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":177396,"visible":true,"origin":"","legend":"\u003cp\u003eStudy area vulnerability under Height of groundwater level above sea level (a), Distance from the shore(b) in 2050\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4771890/v1/0710d55ba743e14b20f097d2.png"},{"id":63042852,"identity":"587c5612-739c-4e41-a54b-8ed2cb879f27","added_by":"auto","created_at":"2024-08-22 11:54:59","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":68150,"visible":true,"origin":"","legend":"\u003cp\u003eGALDIT model results under sea level rise and water level loss scenarios in 2050\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4771890/v1/bad85e6cdaf05bcc49560fcd.png"},{"id":63044276,"identity":"b18994c0-558f-404d-b9dd-55a25080bda9","added_by":"auto","created_at":"2024-08-22 12:11:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3795208,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4771890/v1/ca82672e-54f0-41aa-bc59-3d80d00833fd.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Assessing the impacts of climate change on the vulnerability of coastal aquifers to the seawater intrusion","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eClimate change is causing significant environmental damage, including rising temperatures, changing rainfall and rising sea levels, destroying natural habitats and biodiversity [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Groundwater in most coastal areas, as the most important source of freshwater, is affected by seawater intrusion [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The most important environmental hazard to coastal aquifers is the seawater intrusion into coastal aquifers [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The saltwater intrusion into the coastal aquifer is a natural phenomenon that occurs due to the difference in density between seawater and groundwater [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The salinity condition of coastal aquifers will be worse by increasing demand for freshwater in the coastal areas (water extraction from the aquifer), and predictions of rising sea levels of 0.1 to 2 m by the end of the year 2100 [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The climate change impacts, such as rising sea levels and rainfall changes which lead to changes in the aquifer recharge rate, are the climatic factors that affect saltwater intrusion. Therefore, this issue has investigated by previous studies [\u003cspan additionalcitationids=\"CR10 CR11 CR12 CR13 CR14 CR15\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAs the sea level rise in the near future is a serious threat and controversial issue for coastal [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], therefore the estimate of sea level rise in the future periods is necessary. Permanent and temporary flooding, erosion of coastlines, destructive storms and the seawater intrusion into freshwater aquifers are the physical effects of sea level rise [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Various studies were investigated the extent of sea level changes and its effects on coastal ecosystems. Sea level increase in the future which results in various coastal damages was approved by these studies [\u003cspan additionalcitationids=\"CR21 CR22 CR23 CR24\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Sea-level changes are affected by two significant factors: the change in volume caused by changes in water density and mass change due to water exchanges between the atmosphere and the earth through precipitation, evaporation, river runoff and ice melting [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. According to the IPCC-AR5 reports, in the 21st century, global mean sea levels will increase as a result of the thermal expansion of the oceans and the melting of polar ice sheets and glaciers. Based on the global sea level rise scenarios, sea level will rise by 26 to 82 centimeters over the next 100 years [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOn the other hand, studies have shown that regional sea level changes are different from global sea level changes [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Therefore, the application of global mean sea level rises in coastal aquifers vulnerability calculation under seawater influences will result in uncertainties. Therefore, some researches have been conducted to calculate the precise level of regional sea level rise [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. In order to estimate the local sea level changes, some researchers have defined the hypothetical scenarios of water level increases [\u003cspan additionalcitationids=\"CR22 CR23\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] and others used the results of AOGCM simulations [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAquifer vulnerability is a relative, non-dimensional, and unmeasurable property and depends on the characteristics of the aquifer, its geological environment, and hydrogeology [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The vulnerability of the aquifer is defined as the ease and possibility of infiltration and dispersion of the pollution from the surface to the aquifer. Several methods have been proposed to determine vulnerability: PI [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], DRASTIC [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], SINTACS [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], EPIK [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], IRISH [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e], AVI [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], GOD [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e], GALDIT [\u003cspan additionalcitationids=\"CR42\" citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e] and VESPA [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eEach of these methods is achieved regarding specific conditions and different data. The vulnerability of seawater intrusion in coastal aquifers for the first time evaluated by Chachadi and Lobo-Ferreira to assess the level of aquifer contamination and the seawater intrusion into coastal aquifers (GALDIT) [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. The GALDIT model is based on the development of the DRASTIC model which is introduced by Aller in 1987. The DRASTIC model uses seven hydrogeological parameters in order to calculate the vulnerability of groundwater under seawater infiltration in the regional scale [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. However, the GALDIT model uses six hydrogeological parameters to calculate the vulnerability of seawater intrusion in larger scales [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. Although models such as DRASTIC can be used to estimate the vulnerability of aquifers, the GALDIT model examines the vulnerability of aquifer under seawater intrusion influences in wider scales, especially in coastal areas [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. The GALDIT can assess the degree of vulnerability to seawater intrusion in different conditions, such as sea level changes, changes in recharging rates influenced by climate change and groundwater discharge to the sea. The model uses a combination of various hydrological components in order to assess the vulnerability of aquifers under different conditions [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The widespread application of the groundwater vulnerability index (GALDIT) confirms the ability of the model to estimate vulnerability changes more accurately [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan additionalcitationids=\"CR50 CR51 CR52 CR53 CR54\" citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eApplication of the global mean sea level rise values in coastal vulnerability calculations will not provide accurate results. Therefore, in this study, the SIMCLIM model [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e], was used to calculate the sea level rise in the Persian Gulf region. Moreover, seawater intrusion into coastal freshwater aquifers which is influenced by the increase of Persian Gulf level and groundwater discharge is a serious threat to the coastal groundwater resources in the study area. Therefore, in this study, the vulnerability of the coastal aquifers of Bushehr province (located in southern Iran) has been evaluated by considering the seawater intrusion due to climate change using GALDIT model.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Study Area\u003c/h2\u003e \u003cp\u003eThe study area of ​​this research is located in the Bushehr province in southern Iran, along with the northern coast of the Persian Gulf. The aquifer area of ​​the study is at an east-east distance of 52\u0026deg; 8 '10\u003csup\u003e\u0026rdquo;\u003c/sup\u003e East to 51\u0026deg; 42'50\u003csup\u003e\u0026rdquo;\u003c/sup\u003e and a latitude of 27\u0026deg; 46' 10\u003csup\u003e\"\u003c/sup\u003e to 28\u0026deg; 6' 20\u003csup\u003e\"\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, b,c). Abdan Lamidan aquifer with a total area of ​​285.5 km\u003csup\u003e2\u003c/sup\u003e has 52 observation wells. Total 16 wells data were used for vulnerability assessment regarding hydraulic conductivity. The hydraulic conductivity experiment of three wells in 2002 and 13 other wells in 2007 was carried out by Step-Drawdown Pumping Test methods, respectively. In this research, groundwater level information of 46 wells of the year 2010\u0026ndash;2011 has been used. In order to analyze the salinity of aquifer under the influence of seawater intrusion, carbonate, bicarbonate and chlorine data of 111 operational and observational wells of the aquifer (deep and semi-deep) for the year 2013 were used. The aquifer thickness data was for the period 2010\u0026ndash;2011. The thickness of the aquifer is increased from 100 to 145 meters from north to south. Based on the report of the National Water Resources Management Company (2011), annual Abdan-Lamidan aquifer groundwater discharge was 35.57\u0026nbsp;million cubic meters. The results of aquifer budget assessment report in this area indicate that the total output of the aquifer in the past few years has been much higher than the inputs to the aquifer. As a result, the groundwater level is constantly decreasing in such a way that in the southern parts of Abdan-Lamidan aquifer, the groundwater level is 10 meters below the sea level.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e The location of the study area in the south of Iran(a), the location of the Abdan-Lamidan aquifer in the Bushehr province, relative to the Persian Gulf (b), the position of the observation wells in the Abedan-Lamidan aquifer area to the Persian Gulf coast (c)\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Simulation of regional sea level changes under climate change\u003c/h2\u003e \u003cp\u003eThe vulnerability assessment of the of the Abdan-Lamidan coastal aquifer to the intrusion of Persian Gulf seawater in the future periods requires simulation and estimation of the regional sea level rise. In this research, the SIMCLIM model was used to investigate the level of changes in the Gulf water regime under climate change impacts. SIMCLIM is a tool designed to facilitate the assessment of climate change impacts. SIMCLIM uses the latest CMIP5 climatic models (CLIMsystems 2013). In the SIMCLIM model, seawater level changes over time are estimated based on the increase in air temperature, which leads to thermal expansion and increased polar ice melting [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e]. The global and regional spatial resolution of the model is about 2.5\u0026deg;\u0026times;2.5\u0026deg; and 0.1\u0026deg;, respectively [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. SIMCLIM was run for 24 AOGCMs presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e under two climate change scenario RCP 2.6 and RCP 8.5 from 1955 to 2050.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of the 24 AOGCM models for the fifth Assessment report (AR5) used in this study.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModel\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eResearch center\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eScenario\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSpatial resolution for ocean variable (longitude*latitude)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSpatial resolution for atmospheric variable (longitude*latitude)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBCC-CSM1-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBCC (China)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.6\u0026deg; \u0026times; 2.32\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.28\u0026deg;\u0026times;0.64 \u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBCC-CSM1-1-m\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBCC (China)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.6\u0026deg; \u0026times; 2.32\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e3.2\u0026deg;\u0026times;1.6\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCanESM2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCCCma (Canada)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6,RCP4.5,RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e2.56\u0026deg;\u0026times;1.92\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.28\u0026deg;\u0026times;0.64\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCCSM4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNCAR(USA)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.2\u0026deg;\u0026times;3.84\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e2.88\u0026deg;\u0026times;1.92\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCMCC-CM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCMCC (Italy)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP4.5, RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e1.82\u0026deg;\u0026times;1.49\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e4.8\u0026deg;\u0026times;2.4\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCMCC-CMS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCMCC (Italy)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP4.5, RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e1.82\u0026deg;\u0026times;1.49\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.92\u0026deg;\u0026times;0.96\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCNRM-CM5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCNRM-CERFACS(France)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6, RCP4.5, RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.62\u0026deg;\u0026times;2.92\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e2.56\u0026deg;\u0026times;1.28\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCSIRO-Mk3-6-0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eABM(Australia)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e1.92\u0026deg;\u0026times;1.89\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.92\u0026deg;\u0026times;0.96\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGFDL-CM3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNOAA GFDL (USA)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.6\u0026deg;\u0026times;2\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.44\u0026deg;\u0026times;0.9\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGFDL-ESM2G\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNOAA GFDL (USA)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.6\u0026deg;\u0026times;2.1\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.44\u0026deg;\u0026times;0.9\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGFDL-ESM2M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNOAA GFDL (USA)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.6\u0026deg;\u0026times;2\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.44\u0026deg;\u0026times;0.9\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGISS-E2-R\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNASA/GISS (USA)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e2.88\u0026deg;\u0026times;1.8\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.44\u0026deg;\u0026times;0.9\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGISS-E2-R-CC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNASA/GISS (USA))\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e2.88\u0026deg;\u0026times;1.8\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.44\u0026deg;\u0026times;0.9\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHadGEM2-CC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMOHC (UK)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP4.5, RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.6\u0026deg;\u0026times;2.16\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.92\u0026deg;\u0026times;1.45\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHadGEM2-ES\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eINPE (UK)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6, RCP4.5, RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.6\u0026deg;\u0026times;2.16\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.92\u0026deg;\u0026times;1.45\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eINMCM4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eINM (Russia)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP4.5, RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.6\u0026deg;\u0026times;3.4\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.8\u0026deg;\u0026times;1.2\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMIROC5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMIROC (Japan)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e2.56\u0026deg;\u0026times;2.24\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e2.56\u0026deg;\u0026times;1.28\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMIROC-ESM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMIROC (Japan)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e2.56\u0026deg;\u0026times;1.92\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.28\u0026deg;\u0026times;0.64\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMIROC-ESM-CHEM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMIROC (Japan)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e2.56\u0026deg;\u0026times;1.92\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.28\u0026deg;\u0026times;0.64\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMPI-ESM-LR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMPI-M (Germany)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6, RCP4.5, RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e2.56\u0026deg;\u0026times;2.2\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.92\u0026deg;\u0026times;0.96\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMPI-ESM-MR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMPI-M (Norway)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6, RCP4.5, RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e8.02\u0026deg;\u0026times;4.04\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.92\u0026deg;\u0026times;0.96\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMRI-CGCM3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMRI (Japan)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.6\u0026deg;\u0026times;3.68\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e3.2\u0026deg;\u0026times;1.6\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNorESM1-M\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNCC (Norway)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.2\u0026deg;\u0026times;3.84\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.44\u0026deg;\u0026times;0.96\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNorESM1-ME\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNCC (Norway)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRCP2.6، RCP4.5، RCP6.0، RCP8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e3.2\u0026deg;\u0026times;3.84\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.44\u0026deg;\u0026times;0.96\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e*RCP: Representative concentration pathways are four greenhouse gas concentration (not emissions) trajectories adopted by the IPCC for its fifth assessment Report (AR5) in 2013 [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e]\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe RCP 2.6 is representative of scenarios that lead to very low greenhouse gas concentration levels. It is a \u0026ldquo;peak-and-decline\u0026rdquo; scenario; its radiative forcing level first reaches a value of 3.1 W m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e by mid-century and returns to 2.6 W m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e by 2100. To reach such radiative forcing levels, greenhouse gas emissions are reduced substantially over time. The RCP 8.5 is characterized by increasing greenhouse gas emissions over time that lead to high greenhouse gas concentration levels. It is a \u0026ldquo;rising\u0026rdquo; scenario; its radiative forcing level continuously rises to 8.5 W m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e by 2100 [28; 58\u0026ndash;60].\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e \u003cb\u003eCharacteristics of the 24 AOGCM models for the fifth Assessment report (AR5) used in this study.\u003c/b\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Coastal aquifer vulnerability assessment\u003c/h2\u003e \u003cp\u003eThe evaluation of the aquifer's vulnerability to the saltwater intrusion was carried out using a GALDIT approach. This index, is based on the nature of the aquifer (G), the hydraulic conductivity (A), the level of groundwater above the sea (L), the distance of the aquifer from the sea (D), the magnitude and extent of saltwater intrusion into the aquifer, (I) and the aquifer thickness (T) [41; 54]. These parameters are the essential components of seawater intrusion to coastal aquifers [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eType of aquifer (G): According to the layout of the geological layers, there are different types of aquifers (unconfined, confined or under pressure, leaky aquifer, and perched). The expansion of the saltwater intrusion depends on natural properties and the type of aquifer [\u003cspan additionalcitationids=\"CR62\" citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e]. Therefore, in unconfined aquifers, the lowest layer has a significant effect on the interference of seawater with fresh water. On the other hand, confined aquifers are more sensitive due to larger loss cone during the pumping time.\u003c/p\u003e \u003cp\u003eHydraulic conductivity (A): The magnitude of salinity intrusion in the aquifer is influenced by the hydraulic conductivity of the aquifer formation. Larger hydraulic conductivity causes more significant seawater intrusion to the coastal aquifer [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. The hydraulic conductivity of the aquifer is estimated based on the flow velocity in the aquifer layers. Hydraulic conductivity is the ability of the aquifer to transfer water, which is the result of effective porosity in sediments and aquifer constituents. The high hydraulic conductivity increases the surface of the drop cone during pumping. In this study, first, transmittance coefficient was estimated using the results of geophysical experiments, and then the hydraulic conductivity was calculated by dividing the raster layer of the transmittance coefficient into the aquifer layer thickness in the region.\u003c/p\u003e \u003cp\u003eThe height of the groundwater level above sea level (L): the ratio of groundwater table to mean sea level is one of the most important parameters in assessing the susceptibility to saltwater intrusion. This parameter is dynamic and primarily related to the piezometric conditions of the coastal aquifer due to its spatial variability. The lower the water table in comparison to the sea level, there is more vulnerability to increase the water level, as well as contamination through the saltwater intrusion into aquifers.\u003c/p\u003e \u003cp\u003eDistance from the seashore (D): The closer parts of the aquifer to the coast experience highest impact of seawater intrusion. The aquifer classification is considered based on the aquifer distance from the seashore, according to the classification presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Different aquifer classes are weighted according to their distance from the coast, with numbers 2.5, 5, 7.5 and 10. The effect of seawater and waves advancement (as a wave motion) toward the coast has a range of decreasing effect. When the distance from the coast increases, the vulnerability of the aquifer decreases. In this study, classification and weighting were done by ArcGIS software.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eParameters of GALDIT method\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eIndicator\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eImportance rating\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.5\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVery low\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eLow\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMedium\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eHigh\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWeight\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c8\" namest=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroundwater\u003c/p\u003e \u003cp\u003eoccurrence/aquifer\u003c/p\u003e \u003cp\u003etype\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eBounded aquifer\u003c/p\u003e \u003cp\u003e(Recharge and/or\u003c/p\u003e \u003cp\u003eimpervious\u003c/p\u003e \u003cp\u003eboundary aligned\u003c/p\u003e \u003cp\u003eparallel to the\u003c/p\u003e \u003cp\u003ecoast)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLeaky confined\u003c/p\u003e \u003cp\u003eAquifer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eUnconfined aquifer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eConfined aquifer\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAquifer hydraulic\u003c/p\u003e \u003cp\u003econductivity\u003c/p\u003e \u003cp\u003e(m day\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5\u0026ndash;10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e10\u0026ndash;40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e40\u0026lt;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeight of ground\u003c/p\u003e \u003cp\u003ewater level asl (m)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.5-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e1-1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1\u0026gt;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistance from shore/\u003c/p\u003e \u003cp\u003ehigh tide (m)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;1000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e750\u0026ndash;1000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e500\u0026ndash;750\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;500\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eImpact status of\u003c/p\u003e \u003cp\u003eexisting seawater\u003c/p\u003e \u003cp\u003eintrusion\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1-1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e1.5-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAquifer thickness\u003c/p\u003e \u003cp\u003e(Saturated) (m)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5-7.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e7.5\u0026ndash;10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eImpact of the existing status of seawater intrusion (I): The effect of saltwater intrusion is measured based on the concentration of chlorine, carbonate and bicarbonate anions (Eq.\u0026nbsp;\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. The data are obtained from observational wells and local exploration wells. Due to the hydraulic gradient balance distribution between seawater and freshwater, the chlorine concentration in observation wells increases relative to carbonate and bicarbonate concentrations. Selection of the mentioned anions, especially chlorine, has been proposed based on the fact that this parameter is predominant in groundwater in coastal areas. (Revelle 1941) recommended the ratio of \u003cem\u003eCl\u003c/em\u003e / [\u003cem\u003eHCO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u0026thinsp;\u003cem\u003e+\u0026thinsp;CO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e] as a criterion to identify the extent of seawater intrusion into the coastal aquifers.\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:I=\\:\\frac{{CL}^{-}}{{CO}_{3}^{2-}+\\:{HCO}_{3}^{-}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eAquifer thickness (T): The aquifer thickness or the aquifer saturation zone is between the water table and the impermeable layer. The difference between the water table and the bedrock layer is considered as the thickness of the aquifer. The thickness of the aquifer varies in spatial scales; larger aquifers are more vulnerable [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e, \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e]. Aquifers with a thickness of more than 10 meters are entirely exposed to severe seawater infiltration vulnerability.\u003c/p\u003e \u003cp\u003eAfter GALDIT index parameter estimation, the model parameters should be weighed. Each of the GALDIT index parameters has a weight which is indicated by W in Eq.\u0026nbsp;\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The details of the GALDIT index parameters and the weight of each parameter, regarding its importance, in the probability of occurrence of the saltwater infiltration, are given in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. The weighting of the parameters is carried out depending on the importance of each of the parameters (based on the assigned weight). The GALDIT index after estimating the maps for each of its components is estimated using the weight of 6 parameters (Eq.\u0026nbsp;\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:GALDIT=\\:\\frac{\\sum\\:_{i=1}^{6}{W}_{i}{\\times\\:R}_{i}}{\\sum\\:_{i=1}^{6}{W}_{i}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e Parameters of GALDIT method\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Climate change impact on coastal aquifer vulnerability\u003c/h2\u003e \u003cp\u003eAs the sea level rises due to climate change, the coastline advances to coastal aquifers and occupies part of the aquifer. Among the different parameters of the GALDIT index, it is expected that two parameters of the groundwater table above seawater level and distance from the seashore (L and D) will be varied due to changes in the water balance in the future periods. In this study, the hydraulic conductivity, type of aquifer, the thickness of the aquifer\u0026rsquo;s saturation zone and the magnitude of infiltrated saltwater parameters are assumed to be constant in the aquifer in the future in comparison with the current condition.\u003c/p\u003e \u003cp\u003eAfter calculating the sea level changes under climate change, the flooding of the aquifer was calculated in 2050 (parameter D). To calculate coastal flooding, seawater level changes based on average of AOGCM models were considered under averages of RCP2.6 and RCP8.5 scenarios in 2050. Because of the slight difference in the amount of sea level rise in 2050 under different RCP scenarios, the mean values ​​of RCP2.6 and RCP8.5 (as the best-worst-case scenario) in the year 2050 was considered. After calculating the coastal flooding due to changes in sea level and coastline advance relative to Abdan-Lamidan aquifer boundary, the aquifer classification was carried out based on aquifer distance from the coastline using the buffer order in ArcGIS software. Additionally, the change in the parameter of aquifer distance from the coast (D) was calculated in 2050 relative to the baseline period.\u003c/p\u003e \u003cp\u003eThe height of the groundwater level above sea level (L) is another parameter of the GALDIT index which will vary with sea level changes. This parameter may be affected by various factors such as an increase in seawater levels under climate change and drop in aquifer water levels due to excess capacity extractions or other factors. In this research, the impact of climate change on sea level rise and natural water loss of aquifer due to extraction has been investigated. Climate change projections show that water level increases under different RCP scenarios in the future. The changes in water level are not significantly different under different scenarios in 2050. Therefore, the sea level rise is calculated based on the changes in the water level under average RCP2.6 and RCP8.5 scenarios. The level of aquifer loss in the future periods is calculated based on aquifer water level changes during the past periods. To obtain (L), the water level values ​​in observation wells under the combined effects of climate change and water loss during the water extraction from Abdan-Lamidan aquifer was considered. This was done through the representative hydrograph of the aquifer over a period of 12 years from 2004 to 2015, and the calculation of the annual water level loss rate for the aquifer.\u003c/p\u003e \u003cp\u003eAdditionally, it is assumed that the aquifer's current condition is continued regarding groundwater balance. It is assumed that the calculated annual water loss rate in the future will continue at the same rate. Therefore, the difference in water level in observation wells is calculated relative to the sea level rise under climate change impact as well as the level of water loss in the aquifer in 2050.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Aquifer vulnerability under current condition scenario\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the status of the various parameters of the GALDIT index in the recent scenario. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea shows the vulnerability of the Abdan-Lamidan aquifer based on the aquifer type (G). Since the Abdan-Lamidan aquifer is unconfined, according to Table\u0026nbsp;(2), the aquifer is placed in the same class regarding the parameter (G). As shown in (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea), the aquifer is in the middle-class vulnerability.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe vulnerability of the Abdan-Lamidan aquifer based on the hydraulic conductivity parameter (A) is shown in (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). According to the hydraulic conductivity of the aquifer, which varies from 2.67 to 50 m day\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the aquifer is classified into four classes regarding vulnerability according to Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. According to Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, about 41.3, 34.67, 233.21, and 13.12 square kilometers of the area of the aquifer has very low, low, moderate and high vulnerability, respectively. On the other hand, about 1.2%, 12.19%, 82% and 4.6% of the aquifer area have very low, low, moderate and high levels of vulnerability. The results showed that the hydraulic conductivity values ​​of the aquifer in the coastal areas are less than the values ​​in the northern region. Therefore, the aquifer's ability to transfer salinity in parts near the sea is lower than other parts of the aquifer.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec represents the vulnerability of the Abdan-Lamidan aquifer based on the Height of groundwater level above sea level (L). Groundwater tables above sea level of Abdan-Lamidan aquifer are located in the observation wells at a distance of -0.52 to 23.30 meters. According to the results, the water level in the observation wells increases compared to the mean sea level with the distance from the coast. Based on available water levels data, the groundwater table above the sea level is classified into four classes (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). According to L values, 66.71, 0.62, 0.62, 32.05% of the aquifer has very low, low, moderate and high vulnerability, respectively. It is expected that the effect of this parameter (L) on the output of the GALDIT index is significant due to the high weight of this parameter in calculating the final vulnerability index.\u003c/p\u003e \u003cp\u003eIn (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed) the vulnerability of the Abdan-Lamidan aquifer is shown based on the distance from the seashore parameter (D). According to the table (2), the aquifer is classified into four classes regarding the parameter of distance from the aquifer. The Abdan-Lamidan aquifer southern parts are located on the tangent to the coastline and northern parts are in distance of more than 10 kilometers from the coastline. The large part of the aquifer is exposed to very low vulnerability due to the position of the aquifer relative to the coastline. This parameter has a significant effect on final vulnerability and GALDIT index calculation of the aquifer. According to D values, about 275.27, 3.55, 3.23 and 4.85 square kilometers of aquifer area has very low, low, moderate and high vulnerability. In other words, about 95.94%, 1.24%, 1.13% and 1.69% of the aquifer has very low, low, moderate and high vulnerability, respectively.\u003c/p\u003e \u003cp\u003eThe vulnerability of the Abdan-Lamidan aquifer based on the current state of the aquifer to seawater infiltration parameter (I) is presented in (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee). Based on the amount of carbonate, bicarbonate, and chlorine recorded in the aquifer utilization and observation wells, according to the classification of Table\u0026nbsp;(2), the entire aquifer was classified into one class. The values of this parameter in the aquifer vary from a minimum value of 1.875 to 175. According to the classification guide, the aquifer is severely vulnerable.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e6\u003c/span\u003ef shows the vulnerability of the Abdan-Lamidan aquifer based on the thickness of the aquifer saturation zone parameter (T). The saturation zone of the aquifer is more than 10 meters thick. Thus, according to the table (2), the northern parts to the coastal areas were divided into one class. The entire Abdan-Lamidan aquifer is subject to severe vulnerability with regards to the thickness of the saturation zone.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e Abdan-Lamidan vulnerability under six vulnerability indicators in the current condition, Aquifer Type(a), Hydraulic conductivity(b), Height of groundwater level above sea level(c), Distance from the shore(d), Impact of existing of status of seawater intrusion(e), Thickness of aquifer(f)\u003c/p\u003e \u003cp\u003eAfter estimating and weighing the parameters of the GALDIT index, the index was calculated based on the importance of each parameter. The vulnerability results based on the GALDIT index are presented in (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e). As shown in (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e), in areas close to the coast, areas with lower water levels in the aquifer, and areas with a high hydraulic conductivity have a higher degree of vulnerability than other parts. Based on this index, 168.59, 92.13 and 11.63 km\u003csup\u003e2\u003c/sup\u003e of the aquifer are under low, medium and high vulnerability. In other words, about 61.89%, 33.82% and 4.27% of the aquifer have a low, moderate and severe vulnerability.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e Abdan-Lamidan vulnerability based on GALDIT index in the current condition scenario\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Aquifer vulnerability under climate change impact\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the increasing trend in seawater level in the study area under the impacts of an ensemble of AOGCM models in the future. Results show that water levels will increase under the different RCP scenarios. The regional sea level changes under different RCP scenarios in 2050 is not significantly different in the study area. Based on the average scenario of RCP2.6 and RCP8.5, the water level will increase by about 25.5 cm in 2050 compared to 2013. As a result of sea level rise, coastline advancement occurs relative to the aquifer boundary. The sea level rise in 2050 compared to 2013 will lead to changes in the groundwater table above sea level parameter (L) and more flooding of the Abdan-Lamidan aquifer.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e \u003cb\u003eSea level changes of Persian Gulf under different RCP scenarios until 2050\u003c/b\u003e\u003c/p\u003e \u003cp\u003eBased on the calculated flooding due to the increase in seawater levels under climate change in 2050, approximately 17.20 km\u003csup\u003e2\u003c/sup\u003e of coastal zone will be flooded. This amount of flooding does not only cover about 10 km along the coast of the Persian Gulf region (the least sloping areas) but also covers about 0.7 km\u003csup\u003e2\u003c/sup\u003e of the Abdan-Lamidan area (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e6\u003c/span\u003eb). Therefore, the coastal distance from the aquifer boundary parameter (D) also varies under flooding conditions. Based on this parameter, 86.85, 2.7, 2.88 and 7.81% of the aquifer are under very low, low, medium and high vulnerability, respectively. Thus, the percentage of areas of the aquifer that are more vulnerable in the base period increases. Other parts of the aquifer, which are less vulnerable are reduced and classified in more vulnerable class. As a result of sea level rise, about 9.36 percent of the area of the aquifer, which was previously in a very low vulnerable class, is subjected to more vulnerability. In other words, the area of ​​the aquifer, which is in a very low vulnerable class, is reduced by 9.36 percent. Therefore, the percentage of aquifer area in low, moderate and severe vulnerability classes increased by 1.46%, 1.75%, and 6.12%, respectively.\u003c/p\u003e \u003cp\u003eIn order to calculate the parameter L of the GALDIT index under climate change, the annual water level loss rate was first calculated using the representative hydrograph of the aquifer over a period of 12 years, from 2004 to 2015. The amount of water level loss over the last 12 years is about 14 cm y\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Assuming that the current aquifer condition regarding water budget continues in the future, it is expected that in 2050 the aquifer's water level would have dropped by about 18.5 meters compared to 2013. By applying the effects of water level loss of the aquifer and sea level rise (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e6\u003c/span\u003ea), in 2050, about 56.18, 1.68, 0.85 and 41.19% of the aquifer were under very low, low, medium and severe vulnerability. Thus, the percentage of areas of the aquifer that are more vulnerable in the base period increases. Other parts of the aquifer, which are less vulnerable are reduced and classified in more vulnerable class. As a result of water level rise, about 10.53 percent of the area of the aquifer, which was previously in a very low vulnerable class, is subjected to more vulnerability. Therefore, the percentage of aquifer area in low, moderate and severe vulnerability classes increased by 1.06%, 0.23% and 9.14%, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003e Water level loss trend in the study area in 2004\u0026ndash;2015\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e6\u003c/span\u003e Study area vulnerability under Height of groundwater level above sea level (a), Distance from the shore(b) in 2050\u003c/p\u003e \u003cp\u003eBy running the GALDIT model for 2050 and taking into account the effects of the parameters of D and L under climate change about 51.14% (139.16 km\u003csup\u003e2\u003c/sup\u003e), 34.66% (94.32 km\u003csup\u003e2\u003c/sup\u003e) and 14.15% (38.5 km\u003csup\u003e2\u003c/sup\u003e) of the area of the aquifer would be under low, moderate and severe vulnerability (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e GALDIT model results under sea level rise and water level loss scenarios in 2050\u003c/p\u003e \u003cp\u003eThe comparison of the application of GALDIT vulnerability index in the current condition scenario and the future scenario shows that due to sea level rise, parts of the aquifer which are low vulnerable in the present time will be more vulnerable in the future. In fact, with sea level rise in the future, more extensive parts of the aquifer will be severely vulnerable. Therefore, the area of the aquifer which will be severely vulnerable will be 3.3 times relative to the current condition scenario (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eVulnerability variations of the Abdan-Lamidan aquifer under current and future condition scenarios\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eVulnerable areas (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eClass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLow vulnerability\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eModerate vulnerability\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHigh vulnerability\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeriod (year)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e61.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2050\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e51.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e34.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e Vulnerability variations of the Abdan-Lamidan aquifer under current and future condition scenarios\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussions","content":"\u003cp\u003eCoastal aquifers are one of the most important sources of freshwater water in most of the coastal areas of the planet. These aquifers are threatened by the seawater intrusion due to sea level rise under climate change in the future. In this research, the GALDIT index is used to investigate climate change impacts on the vulnerability of Abdan-Lamidan coastal aquifer under two scenarios (current condition (2013) and the future scenario (2050)). The GALDIT model was run based on the values ​​of six variables of hydraulic conductivity, type of aquifer, the thickness of the aquifer saturation zone, Impact of the existing status of seawater intrusion, Height of groundwater level above sea level and the aquifer distance from the shore in the present condition (2013). According to the results of the GALDIT model, under the current condition scenario, about 61.89%, 33.82% and 4.27% of the aquifer are a low, moderate and severe vulnerability, respectively.\u003c/p\u003e \u003cp\u003eIn order to investigate the effects of climate change on the vulnerability of the study area in 2050, it was assumed that the hydraulic conductivity, type of aquifer, the thickness of the aquifer saturation zone and the impact of existing status of seawater intrusion parameters in 2050 were constant relative to the existing conditions. However only two parameters of the height of the groundwater level above sea level and the aquifer distance from the seashore were varied. In this regard, the height of groundwater level above sea level parameter was simulated under the impacts of sea level rise and the loss of water level in aquifers due to factors such as climate change and overcapacity extraction in 2050.\u003c/p\u003e \u003cp\u003eClimate change impact results on water level changes revealed that the water level would increase about 25.5 cm in 2050 in the region compared to 2013 based on the average of the AOGCM models under the two scenarios RCP2.6 and RCP8.5. On the other hand, by assuming that the current aquifer conditions will continue in the future, the water level will fall by 14 cm annually and about 18.5 m in 2013\u0026ndash;2050. Other researchers, for instance, Santha Sophiya and Syed (2013), also indicated an increase in the vulnerability of coastal aquifers as a result of seawater intrusion, due to the increase in water levels in 2050. In addition, according to Ebert et al. (2016) research on the effect of water level increase under climate change in future periods on the percentage of wells located in the coastal zone and affected by seawater intrusion, showed that 2 meters increase in the Baltic Sea water level about 99 km\u003csup\u003e2\u003c/sup\u003e (about 3 percent) of the coast of the Gotland Island in Sweden will flood. This flooding will cause salinity in 231 wells out of 7354 wells.\u003c/p\u003e \u003cp\u003eBy running the GALDIT model based on the changes in two parameters of the groundwater table above the sea and the distance of the aquifer from seashore approximately 14.15%, 34.66% and 51.14% of the aquifer will be under low, moderate and severe vulnerability in 2050. The vulnerability comparisons obtained from the GALDIT vulnerability index in the current condition to the future scenarios indicate that parts of the aquifer that are currently low vulnerable will be more vulnerable in the future. In fact, with sea level rise in the future, more areas of the aquifer will be severely vulnerable. Therefore, the area of the aquifer which will be severely vulnerable will be 3.3 times relative to the current condition scenario. GALDIT index results show that 14.15% of the aquifer is under severe vulnerability in 2050, while only 4.27% of the aquifer was severely vulnerable in 2013. Recinos (2015(was shown that based on the GALDIT index results in 1992 and 2004, the aquifer's vulnerability increased during the 13-year period. The vulnerability was 60% of the aquifer in 2004, while only 45% of the aquifer was severely vulnerable and other areas were moderate in 1992.\u003c/p\u003e \u003cp\u003eBased on the projected conditions in future periods, proper management of water harvesting from the aquifer to maintain a balance between salt and fresh water levels and the implementation of artificial feeding plans in parts of the aquifer will improve the status of the aquifer. Considering the more significant impact of water discharge relative to the effect of climate change, in changes of groundwater table above sea level parameter, providing effective solutions to improve water management in coastal areas, have a more significant impact on environmental risk reduction of seawater intrusion into freshwater.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors thank the Ministry of Energy (MOE) for collaborating on providing the necessary information (information on groundwater parameters) in conducting research. Additionally, authors thank the SIMCLIM 2013 software development team for providing the software and sea level data set for future forecasts of sea level (the Persian Gulf and Oman).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests statement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding statement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe have no conflict of interest to declare. \u0026ldquo;No funding was obtained for this study\u0026rdquo;.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclarations statement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors have read, understood, and have complied as applicable with the statement on \u0026quot;Ethical responsibilities of Authors\u0026quot; as found in the Instructions for Authors.\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statements:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eRoohi M, Faeli M, Jamshidi F, Ghasroddashti AP. 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Transport Porous Media 43(1):29\u0026ndash;44. doi:10.1023/A:1010601208708\u003c/li\u003e\n\u003cli\u003eSantha Sophiya M, Syed TH (2013) Assessment of vulnerability to seawater intrusion and potential remediation measures for coastal aquifers: a case study from eastern India. Environmental Earth Sciences 70(3):1197-1209. doi:10.1007/s12665-012-2206-x\u003c/li\u003e\n\u003cli\u003eKura NU, Ramli MF, Ibrahim S, Sulaiman WNA, Aris AZ, Zaudi AITMA (2014) Assessment of groundwater vulnerability to anthropogenic pollution and seawater intrusion in a small tropical island using index-based methods. Environmental Science and Pollution Research 22(2):1512-1533. doi:10.1007/s11356-014-3444-0 Najib\u003c/li\u003e\n\u003c/ol\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-civil-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Civil Engineering](https://www.springer.com/journal/44290)","snPcode":"44290","submissionUrl":"https://submission.nature.com/new-submission/44290","title":"Discover Civil Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Aquifer vulnerability, Climate change, Coastal aquifer, GALDIT index","lastPublishedDoi":"10.21203/rs.3.rs-4771890/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4771890/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn most coastal areas, groundwater is affected by saltwater intrusion. Climate change effects, such as the sea-level rise and rainfall change are the climatic factors affecting the saltwater intrusion into groundwater. This study examines the vulnerability of the Abdan-Lamidan coastal aquifer to the intrusion of Persian Gulf saline waters under different hydrological conditions. First, the SIMCLIM model was used to calculate the regional sea-level rise of the Gulf under 24 future AOGCMs projections. The results showed that the increase in water level under the ensemble of AOGCM models and two RCP2.6 and RCP8.5 scenarios is 6.7 and 7.8 cm in 2050 compared to 2013. Then, the GALDIT vulnerability index was used to assess the vulnerability of the aquifer under the current condition and future scenarios. The results showed that parts of the aquifer that are currently at lower levels would be more vulnerable to sea-level rise in the future periods.\u003c/p\u003e","manuscriptTitle":"Assessing the impacts of climate change on the vulnerability of coastal aquifers to the seawater intrusion","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-22 11:38:54","doi":"10.21203/rs.3.rs-4771890/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"32377006398731422646084575779799490056","date":"2024-08-31T08:16:00+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-08-30T04:14:10+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-08-28T21:52:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"147507807461867825348190271006455469216","date":"2024-08-23T19:08:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"66708992915882847689778832046609334159","date":"2024-08-23T15:26:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"33324194487289435080092501406799598302","date":"2024-08-23T14:08:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"1025567154406949550214922780534780557","date":"2024-08-04T00:51:08+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-08-02T09:12:10+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-07-30T06:40:45+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-07-27T04:28:35+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Civil Engineering","date":"2024-07-20T07:39:34+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-civil-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Civil Engineering](https://www.springer.com/journal/44290)","snPcode":"44290","submissionUrl":"https://submission.nature.com/new-submission/44290","title":"Discover Civil Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"032bc12c-1d27-44e7-865c-9d707e8fd7a2","owner":[],"postedDate":"August 22nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-10-22T06:53:31+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-22 11:38:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4771890","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4771890","identity":"rs-4771890","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}