Hydrological Response of the Thiokoye River Basin to Climate Change: An Assessment Using the GR4J Hydrological Model and CMIP5 Climate Projections

Hydrological Response of the Thiokoye River Basin to Climate Change: An Assessment Using the GR4J Hydrological Model and CMIP5 Climate Projections | 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 Hydrological Response of the Thiokoye River Basin to Climate Change: An Assessment Using the GR4J Hydrological Model and CMIP5 Climate Projections Ibrahima Thiaw This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6847412/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 This study evaluates the impacts of climate change on surface water resources in the Thiokoye River Basin, a tributary of the Gambia River in West Africa, using the GR4J daily hydrological model implemented in R via the airGR package. Model calibration (1974–1984) and validation (1985–1991), following a warm-up period (1972–1973), were conducted using the SCE-UA algorithm and a multi-criteria objective function combining NSE, log-NSE, KGE, and R², all exceeding 75%, indicating satisfactory model performance. Future climate projections, derived from five CORDEX-Africa regional models (GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR, NorESM1-M, and MIROC) under RCP4.5 and RCP8.5 scenarios, were bias-corrected using the CDF-t method and fed into the model to simulate streamflow until 2100. Results show a general decline in mean annual discharge— comprised between − 30% under RCP4.5 and − 19.6% under RCP8.5 compared to the historical average of 8.71 m³/s—despite stronger warming under RCP8.5 (+ 4.15°C vs. +2.5°C), a paradox explained by the higher flows projected by some models, especially MIROC5. This is consistent with uncertain rainfall trends, with Multi-Model Means (MMM) indicating annual decreases of − 12.71% (RCP4.5) and − 16.55% (RCP8.5), while MIROC5 alone forecasts increased precipitation. Flow variability is expected to intensify, with standard deviations rising to 4.22 m³/s (RCP4.5) and 6.5 m³/s (RCP8.5). Seasonally, runoff is projected to decrease during the wet season, with greater extremes—minimum flows dropping to 0.1 m³/s and peaks potentially reaching 33.1 m³/s under RCP8.5—alongside lower dry-season flows and potential shifts in flow timing. These findings underscore the hydrological vulnerability of the Thiokoye Basin to future climate change and the importance of incorporating ensemble-based, uncertainty-aware modeling approaches into water resource planning. The study reinforces the urgency of adaptive, climate-resilient strategies for basin management, infrastructure design, and agricultural planning to safeguard livelihoods and ecosystems in the face of intensifying climate pressures. Hydrology Climate Analysis and Modeling Environmental Engineering Thiokoye River Basin Climate Change Hydrological Modeling GR4J CORDEX-Africa CDF-t Bias Correction Full Text Additional Declarations The authors declare no competing interests. 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. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6847412","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":468141705,"identity":"08d1679c-10cb-4f53-bf93-730e7214f3ce","order_by":0,"name":"Ibrahima Thiaw","email":"data:image/png;base64,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","orcid":"https://orcid.org/0009-0005-3496-2712","institution":"Cheikh Anta Diop University","correspondingAuthor":true,"prefix":"","firstName":"Ibrahima","middleName":"","lastName":"Thiaw","suffix":""}],"badges":[],"createdAt":"2025-06-08 12:30:48","currentVersionCode":1,"declarations":{"humanSubjects":true,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":true,"humanSubjectConsent":true,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-6847412/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6847412/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84367680,"identity":"751218e2-ae5d-47bd-9782-c90d141b84ca","added_by":"auto","created_at":"2025-06-11 06:26:15","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1977248,"visible":true,"origin":"","legend":"","description":"","filename":"HydrologicalResponseoftheThiokoyeRiverRevV2.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6847412/v1_covered_2d97038d-f64e-440c-b17c-caec5aed88f5.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eHydrological Response of the Thiokoye River Basin to Climate Change: An Assessment Using the GR4J Hydrological Model and CMIP5 Climate Projections\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Cheikh Anta Diop University","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":"Thiokoye River Basin, Climate Change, Hydrological Modeling, GR4J, CORDEX-Africa, CDF-t Bias Correction","lastPublishedDoi":"10.21203/rs.3.rs-6847412/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6847412/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study evaluates the impacts of climate change on surface water resources in the Thiokoye River Basin, a tributary of the Gambia River in West Africa, using the GR4J daily hydrological model implemented in R via the airGR package. Model calibration (1974\u0026ndash;1984) and validation (1985\u0026ndash;1991), following a warm-up period (1972\u0026ndash;1973), were conducted using the SCE-UA algorithm and a multi-criteria objective function combining NSE, log-NSE, KGE, and R\u0026sup2;, all exceeding 75%, indicating satisfactory model performance. Future climate projections, derived from five CORDEX-Africa regional models (GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR, NorESM1-M, and MIROC) under RCP4.5 and RCP8.5 scenarios, were bias-corrected using the CDF-t method and fed into the model to simulate streamflow until 2100. Results show a general decline in mean annual discharge\u0026mdash; comprised between \u0026minus;\u0026thinsp;30% under RCP4.5 and \u0026minus;\u0026thinsp;19.6% under RCP8.5 compared to the historical average of 8.71 m\u0026sup3;/s\u0026mdash;despite stronger warming under RCP8.5 (+\u0026thinsp;4.15\u0026deg;C vs. +2.5\u0026deg;C), a paradox explained by the higher flows projected by some models, especially MIROC5. This is consistent with uncertain rainfall trends, with Multi-Model Means (MMM) indicating annual decreases of \u0026minus;\u0026thinsp;12.71% (RCP4.5) and \u0026minus;\u0026thinsp;16.55% (RCP8.5), while MIROC5 alone forecasts increased precipitation. Flow variability is expected to intensify, with standard deviations rising to 4.22 m\u0026sup3;/s (RCP4.5) and 6.5 m\u0026sup3;/s (RCP8.5). Seasonally, runoff is projected to decrease during the wet season, with greater extremes\u0026mdash;minimum flows dropping to 0.1 m\u0026sup3;/s and peaks potentially reaching 33.1 m\u0026sup3;/s under RCP8.5\u0026mdash;alongside lower dry-season flows and potential shifts in flow timing. These findings underscore the hydrological vulnerability of the Thiokoye Basin to future climate change and the importance of incorporating ensemble-based, uncertainty-aware modeling approaches into water resource planning. The study reinforces the urgency of adaptive, climate-resilient strategies for basin management, infrastructure design, and agricultural planning to safeguard livelihoods and ecosystems in the face of intensifying climate pressures.\u003c/p\u003e","manuscriptTitle":"Hydrological Response of the Thiokoye River Basin to Climate Change: An Assessment Using the GR4J Hydrological Model and CMIP5 Climate Projections","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-11 06:01:58","doi":"10.21203/rs.3.rs-6847412/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","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}}],"origin":"","ownerIdentity":"6dcdc784-9bbd-4e1c-abf9-ad97f1807401","owner":[],"postedDate":"June 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":49702394,"name":"Hydrology"},{"id":49702395,"name":"Climate Analysis and Modeling"},{"id":49702396,"name":"Environmental Engineering"}],"tags":[],"updatedAt":"2025-06-11T06:02:06+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-11 06:01:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6847412","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6847412","identity":"rs-6847412","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}