Impacts of Changing Rainfall Patterns on Hydropower Generation: A Case Study of Kehelgamu Oya Sub-basin

Abstract

Hydropower, the largest renewable energy source in Sri Lanka, generates approximately 50% of the total energy requirement. The annual electricity generation fluctuates greatly due to the variation of rainfall. Thus, the daily rainfall at Castlereagh and Norton stations of the Kelani River basin during the period 1960-2016 has been analysed on an annual, seasonal, and monthly basis. The aim of this research is to identify the impact of rainfall patterns on hydropower generation in Sri Lanka. Variability of the time series is assessed by detecting the trend using Spearmen’s correlation coefficient test. Sen’s slope estimator test was used to estimate the magnitude of the trend. Pearson correlation coefficient was used to find the relationship between rainfall and hydropower generation. A significant decrease in the annual rainfall and South-West monsoon rainfall observed at Norton and Castlereagh also shows a similar but not significant decreasing trend. A decreasing trend of monthly rainfall was also found at both stations. The results revealed that the future hydropower generation is in an alarming situation due to the decreasing trend of rainfall.