Climate Change in Sri Lanka

Abstract

Rainfall extremes have adverse impacts on the society and environment of Sri Lanka. Different regions of the country have witnessed either flooding or drought in quick succession in recent years. Some studies attribute such extreme events to climate changed induced by global warming. However, there is a dearth of climatological studies addressing the spatio-temporal trends in rainfall over Sri Lanka in support of such attribution. Using daily rainfall data collected at the 22 main meteorological stations of the Department of Meteorology, this paper identifies spatio-temporal trends in the rainfall received during the four rainy seasons – i.e. the Southwest monsoon, the first inter-monsoon, the Northeast monsoon and the second inter-monsoon during the period 1961-2002. It translates rainfall trends into trends in water volume by river basin using different GIS techniques, so that the practical implications of climate variability and change in recent decades are clearly identifiable. The study finds that the number of rainy days has decreased at all the meteorological stations except for the Nuwara Eliya station. It also finds that the 2000mm isohyet – demarcating the wet zone of the country - has shrunk. Water volume by watershed shows a clear dichotomous distribution with watersheds in the north having increasing trends, and watersheds in the south having decreasing trends, in water volume.