{"paper_id":"096a13dc-0dbe-4da1-b656-c6617bd5b58d","body_text":"Assessing the Impacts of Projected Climate Scenarios on Irrigation Reliability and Reservoir Sustainability in Sri Lanka’s Dry Zone | 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 Assessing the Impacts of Projected Climate Scenarios on Irrigation Reliability and Reservoir Sustainability in Sri Lanka’s Dry Zone Sareeha Vasanthakumar, Mohanasundaram Shanmugam, Sangam Shrestha, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7906854/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 Climate change poses major challenges for irrigation water management in Sri Lanka’s dry zone. This study assesses the performance of the Nachchaduwa reservoir under historical and projected climate scenarios using multiple General Circulation Models (GCMs). Eight GCMs were ranked through compromise programming, with the top three models bias-corrected and downscaled to generate climate projections for the Shared Socioeconomic Pathways (SSP) scenarios: SSP2-4.5 and SSP5-8.5, under near-future (2015–2050) and mid-future (2051–2075) conditions. The ensemble GCM data used for HEC-HMS to simulate inflows, HEC-ResSim to reservoir water levels, and releases for these future scenarios. Current and future irrigation requirements were estimated using CROPWAT for the assessment of Reliability, Resilience, and Vulnerability (RRV) metrics, as well as the Reservoir Sustainability Index (RSI). Trend analysis indicates that precipitation is increasing by 2.6% -14.2%, particularly under the SSP5-8.5 scenario. Temperatures are rising, with minimums increasing by 3.9% -9.6% and maximums by 1.5% -5.4%. The HEC-HMS model suggests that annual flows will experience a slight decrease under SSP2-4.5 and an increase under SSP5-8.5. Mean annual irrigation demand is projected to rise by 40.5%- 43.6% in the near and mid-future across both SSP scenarios. Reliability remains near 60%, resilience varies 48–58%, indicating moderate recovery after deficits. Vulnerability remains below 30%, indicating inadequate irrigation flows, with RSI values ranging from 0.22 to 0.35. Combining RRV metrics with RSI shows the Nachchaduwa reservoir is moderately sustainable under future climate scenarios. However, adaptive strategies like optimised operations and management are vital to maintain irrigation reliability. Nachchaduwa reservoir climate change scenarios irrigation demand Reliability-Resiliency-Vulnerability metrics Reservoir Sustainability Index HEC-HMS HEC-ResSim CROPWAT Full Text Additional Declarations No competing interests reported. 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-7906854\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":true,\"archivedVersions\":[],\"articleType\":\"Research Article\",\"associatedPublications\":[],\"authors\":[{\"id\":537717752,\"identity\":\"e9e6286c-52e6-4cf4-8de9-4137c7bff67e\",\"order_by\":0,\"name\":\"Sareeha Vasanthakumar\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Asian Institute of Technology\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Sareeha\",\"middleName\":\"\",\"lastName\":\"Vasanthakumar\",\"suffix\":\"\"},{\"id\":537717754,\"identity\":\"e0ae8ac0-3af6-4910-80e5-3dfbb904ae6b\",\"order_by\":1,\"name\":\"Mohanasundaram 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This study assesses the performance of the Nachchaduwa reservoir under historical and projected climate scenarios using multiple General Circulation Models (GCMs). Eight GCMs were ranked through compromise programming, with the top three models bias-corrected and downscaled to generate climate projections for the Shared Socioeconomic Pathways (SSP) scenarios: SSP2-4.5 and SSP5-8.5, under near-future (2015\\u0026ndash;2050) and mid-future (2051\\u0026ndash;2075) conditions. The ensemble GCM data used for HEC-HMS to simulate inflows, HEC-ResSim to reservoir water levels, and releases for these future scenarios. Current and future irrigation requirements were estimated using CROPWAT for the assessment of Reliability, Resilience, and Vulnerability (RRV) metrics, as well as the Reservoir Sustainability Index (RSI). Trend analysis indicates that precipitation is increasing by 2.6% -14.2%, particularly under the SSP5-8.5 scenario. Temperatures are rising, with minimums increasing by 3.9% -9.6% and maximums by 1.5% -5.4%. The HEC-HMS model suggests that annual flows will experience a slight decrease under SSP2-4.5 and an increase under SSP5-8.5. Mean annual irrigation demand is projected to rise by 40.5%- 43.6% in the near and mid-future across both SSP scenarios. Reliability remains near 60%, resilience varies 48\\u0026ndash;58%, indicating moderate recovery after deficits. Vulnerability remains below 30%, indicating inadequate irrigation flows, with RSI values ranging from 0.22 to 0.35. Combining RRV metrics with RSI shows the Nachchaduwa reservoir is moderately sustainable under future climate scenarios. 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