Usangu rainfall variability analysis: Unveiling spatio-temporal trend, distribution and concentration of rainfall in a semi-arid region

Usangu rainfall variability analysis: Unveiling spatio-temporal trend, distribution and concentration of rainfall in a semi-arid region | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Usangu rainfall variability analysis: Unveiling spatio-temporal trend, distribution and concentration of rainfall in a semi-arid region Rosemary Kavishe, Deogratias Mulungu, Augustina Alexander This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4456989/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Rainfall unpredictability in semi-arid climates affects the quality and quantity of water available for socioeconomic activities, ecological maintenance and developmental projects. Understanding rainfall characteristics such as trend, distribution, and concentration is important for managing water resources and planning to mitigate impacts from rainfall uncertainty. This study was conducted in the Usangu catchment located in a semi-arid environment with three competing users agricultural land upstream, and the National Park and hydropower plant. A multidisciplinary approach that integrated statistical methods, hydrological analysis and geographic information system (GIS) tools was used to unveil a spatio-temporal trend and variability of annual rainfall in Usangu. The results indicated a significant trend for all stations except Mafinga station. The highest decrease was at Kimani (S=-6.13) and the highest increase at Matamba (S = 2.93). There is a distinct distribution of rainfall between the highlands (800-1,200 mm/year) and lowlands (500–800 mm/year). Rainfall is concentrated in short periods indicated by higher precipitation concentration index (PCI) values ranging from (18.8 to 23.6). There is less dispersion of rainfall at station N based on the coefficient of variation (CV = 17.1%) and high dispersion at Kimani (CV = 33.6%) but the majority of the catchment experienced consistent rainfall patterns. According to the standardised anomaly index (SAI), oftentimes the catchment experienced normal conditions (32 years out of 42 years) which accounts for 77%. Also, extreme drought conditions are more dominant in the lowlands than in the highlands. The results of this study are useful for long-term planning of water resources utilization in Usangu. Full Text Additional Declarations No competing interests reported. Supplementary Files ListofTable.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4456989","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":309636395,"identity":"17e5fa7f-9639-4312-b1e6-2df62eab2132","order_by":0,"name":"Rosemary Kavishe","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCklEQVRIiWNgGAWjYDADCSA+wNjAIAfiHHhAihZjsJYEYrUwALUkNoAY+LSYt7c/fHSj5l7izPYzhgd/7rBJnx92+CHQFjs53QbsWmTOnDE2zjlWnDibJ8fgMO+ZtNyNt9MMgFqSjc0O4HCPRA6bdA5bQuI8hrSEw4xth3M3zk4AaTmQuA2nlvTnv3P+AbXwP0s4+LPtf7rh7PQPBLQkmDHntiUkzpZIPnCAt+1Agrx0DgFbeM4YS+f2JRjPnPH4wGHetmTDDdI5BQcSDPD4hb394eecbwmyM84nNn/82WYnLz87ffOHDxV2cri0wIBjA4xlAFZpgF85CNjDWfINuFWNglEwCkbByAQAvTNoU9MkfnUAAAAASUVORK5CYII=","orcid":"","institution":"University of Dar es Salaam","correspondingAuthor":true,"prefix":"","firstName":"Rosemary","middleName":"","lastName":"Kavishe","suffix":""},{"id":309636396,"identity":"705fabb0-709e-42c9-a5c2-4eb0155122f6","order_by":1,"name":"Deogratias Mulungu","email":"","orcid":"","institution":"University of Dar es Salaam","correspondingAuthor":false,"prefix":"","firstName":"Deogratias","middleName":"","lastName":"Mulungu","suffix":""},{"id":309636397,"identity":"4e9e9351-b87a-4a73-ab8a-d0868e4384af","order_by":2,"name":"Augustina Alexander","email":"","orcid":"","institution":"University of Dar es Salaam","correspondingAuthor":false,"prefix":"","firstName":"Augustina","middleName":"","lastName":"Alexander","suffix":""}],"badges":[],"createdAt":"2024-05-21 20:38:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4456989/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4456989/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":67204651,"identity":"224c8e14-13d3-4243-a2c0-724073b85efe","added_by":"auto","created_at":"2024-10-22 10:39:07","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2437888,"visible":true,"origin":"","legend":"","description":"","filename":"Manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4456989/v1_covered_82e75b07-8326-4c16-a9eb-ddf5cac6da22.pdf"},{"id":57587954,"identity":"02a4c111-5161-4d05-9439-a7a2cf222157","added_by":"auto","created_at":"2024-06-03 04:08:43","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":52154,"visible":true,"origin":"","legend":"","description":"","filename":"ListofTable.docx","url":"https://assets-eu.researchsquare.com/files/rs-4456989/v1/2bb6600a21f54a90d478910a.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Usangu rainfall variability analysis: Unveiling spatio-temporal trend, distribution and concentration of rainfall in a semi-arid region","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4456989/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4456989/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRainfall unpredictability in semi-arid climates affects the quality and quantity of water available for socioeconomic activities, ecological maintenance and developmental projects. Understanding rainfall characteristics such as trend, distribution, and concentration is important for managing water resources and planning to mitigate impacts from rainfall uncertainty. This study was conducted in the Usangu catchment located in a semi-arid environment with three competing users agricultural land upstream, and the National Park and hydropower plant. A multidisciplinary approach that integrated statistical methods, hydrological analysis and geographic information system (GIS) tools was used to unveil a spatio-temporal trend and variability of annual rainfall in Usangu. The results indicated a significant trend for all stations except Mafinga station. The highest decrease was at Kimani (S=-6.13) and the highest increase at Matamba (S\u0026thinsp;=\u0026thinsp;2.93). There is a distinct distribution of rainfall between the highlands (800-1,200 mm/year) and lowlands (500\u0026ndash;800 mm/year). Rainfall is concentrated in short periods indicated by higher precipitation concentration index (PCI) values ranging from (18.8 to 23.6). There is less dispersion of rainfall at station N based on the coefficient of variation (CV\u0026thinsp;=\u0026thinsp;17.1%) and high dispersion at Kimani (CV\u0026thinsp;=\u0026thinsp;33.6%) but the majority of the catchment experienced consistent rainfall patterns. According to the standardised anomaly index (SAI), oftentimes the catchment experienced normal conditions (32 years out of 42 years) which accounts for 77%. Also, extreme drought conditions are more dominant in the lowlands than in the highlands. 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