Water Resources Availability and Low Flow Discharge Analysis of Two Selected River Basins in the Dry Zone Under Changing Climate Conditions

Climate change is the most significant challenge to achieving sustainable development and it is one of the most discussed topics today due to the frequent changes triggered around the globe because of both manmade and natural causes. Water resources and river flow are the main hydrologic parameters often affected by climate change. In the present study, the predicted climate change variations are derived from literature and HEC-HMS rainfall-runoff model is used to investigate impending impacts on using two dry zone basins. For Kirindi Oya and Maduru Oya basins, the model was calibrated using a data period from 2001/2-2008 and validated from 2009–2015. The MRAE (Mean Ratio Absolute Error), NSE (Nash-Sutcliffe Efficiency), R2 (Coefficient of Determination) and PBIAS (Percentage of BIAS) were used as objective functions. Even though the main study area is the dry zone of Sri Lanka, the analysis included the other climatic zones, mainly the wet zone as well, as they have a direct or indirect impact on the river flows in the dry zone. Synthetic climate change scenarios based on predicted climate variations were considered for future streamflow generation and results indicate that HEC-HMS in combination with SPI analysis is a useful tool in low flow analysis.