Water Resources Availability and Low Flow Discharge Analysis of Kelani River Basin in Wet Zone under Changing Climate Conditions

Abstract

This study estimates the effects of climate change on water resources availability and low flow streamflow discharge in the wet zone Kelani Basin in Sri Lanka. The selected pilot areas for this study are the Norwood subbasin and the Deraniyagala subbasin of Kelani river. This research further evaluates the future change in streamflow of Kelani river due to climate change using the synthetic climate scenario analysis. Standard Precipitation Index (SPI) analysis was performed to identify meteorological drought conditions that appeared in the study area. HEC-HMS rainfall-runoff was used to simulate streamflow, due to the accessibility, reliability, and flexibility of the model. The model results indicated that the capability of HEC-HMS to simulate streamflow in the basin with reasonably higher accuracy. According to the rainfall elasticity of streamflow analysis, elasticity values of 0.75 and 1.00 were obtained for the Norwood and Deraniyagala subbasins, which indicate that a 1.00% change in rainfall results in a 0.75% and 1.00% change in streamflow discharge in two basins, respectively. For the testing of future water management plans and policymaking on low flow management, this model is a feasible tool while the findings and outcome of the research will be useful for scenario analysis and implementation.