Author(s): A. G. Thrimali Dinethra. ; B. M. L. Arunoda Basnayake
Keywords: Climate change; Human activity; Upper nilwala basin; Climate elasticity method
Abstract: Flooding is one of the major problem occurred in the river basins of Sri Lanka. Nilwala basin is identified as one of the major rivers that is vulnerable to floods. According to the records, floods have occurred almost every year in the Nilwala basin. Climate change, intensified land use, and changes in the river network have led to increase in flooding. Discharge of upper Nilwala basin has dramatically increased by 23 cm/yr over 10 years from 2004 to 2013. Separating effects of climate change and human activity on river discharge at the watershed scale is needed for developing measures to reduce the effect of flooding. This study conducts a quantitative assessment of the impact of climate change and human activities on the runoff increase in the upper catchment of the Nilwala basin based on the climate elasticity method. The results showed that climate change contributes 38%to the increase in runoff, while human activities contributes 62%for the period 2004-2008 compared to the baseline period 1999-2003 and those were 22%and 78%for the altered period 2009-2013.