Evaluation of Future Streamflow in the Upper Part of the Nilwala River Basin (Sri Lanka) under Climate Change

Climate change is a serious and complex crisis that impacts humankind in different ways. It affects the availability of water resources, especially tropical regions South Asia to greater extent. However, impact climate on resources Sri Lanka has been least explored. Noteworthy, this first study attempts evaluate streamflow watershed located southern coastal belt island. The objective paper Upper Nilwala River Basin (UNRB), Lanka. In study, bias-corrected rainfall data from three Regional Models (RCMs) under two Representative Concentration Pathways (RCPs): RCP4.5 RCP8.5 were fed into Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) model obtain future streamflow. Bias correction (NRB) was conducted using Linear Scaling Method (LSM). Future precipitation projected timelines: 2020s (2021–2047), 2050s (2048–2073), 2080s (2074–2099) compared against baseline period 1980 2020. ensemble mean annual NRB expected rise by 3.63%, 16.49%, 12.82% RCP 4.5 emission scenario during 2020s, 2050s, 2080s, 4.26%, 8.94%, 18.04% 8.5 respectively. UNRB increase 59.30% 65.79% scenarios, respectively, when scenario. addition, seasonal flows are also for both RCPs all seasons with an exception southwest monsoon season 2015–2042 general, results present demonstrate experience changes current climatic conditions. will be major importance river basin planners government agencies develop sustainable management strategies adaptation options offset negative climate.