Optimal Management of Water Resources among the Various Users of Lower Kanakarayanaru River Basin, Northern Sri Lanka

Though potential water availability in the Kanakarayanaru ungauged river basin of Northern Sri Lanka is significant, many users experience water inadequacy due to suboptimal management and climate variability. According to literature reviews and prior studies in this region, there has been little discussion on workable strategies for managing water resources; hence, a comprehensive approach is required. This study aims to propose optimal water management strategies to minimize water inadequacy for multiple users in the Kanakarayanaru River basin. Computer-aided hydrological analysis tools such as the Soil Water Assessment Tool (SWAT) and Water Evaluation and Planning (WEAP) are predominantly used to assess the water availability in the region and share the water resources among multiple users. The SWAT simulated runoff values were in good agreement with the observed runoff for the period of 2018 to 2023 andoil Conservation Service Curve Number (NRCS-CN) method. The present study also evaluated the supply and demand of available water for the year 2023 and future scenarios (2024–2050) using WEAP for the application of optimal management strategies. The outcome of the WEAP simulation shows that there is no shortage of water for the reference Scenario. However, Scenario 1 predicts a notable increase in unmet water demand beyond 2033, due to increased water demand. Conversely, Scenario 2 exhibits no unmet water demand during the simulation time frame up to the year of 2040 due to the improved irrigation efficiency scenario. Also, Monthly Unmet demand was observed in both Scenarios 1 & 2 due to supply delivery issues. In the meantime, the introduction of demand management strategies significantly reduced the annual unmet water demand, highlighting the importance of efficient allocation and use of water resources.Our study provides a framework for policymakers and water-related institutions to sustainably address supply and demand imbalances for social, economic, and environmental benefits.