Impact of Climatic Variations and Land Use on the Water Resources in the Mi Oya River Basin Sri Lanka

Abstract

One of the most urgent challenges facing the world today is ensuring anadequate supply and quality of water in light of both burgeoning human needs andclimate variability and change. Despite water's importance to life on earth, there aremajor gaps in our basic understanding of water availability, quality and dynamics, andthe impact of changing climate, and human activity, on the water systems. In thiscontext, the understanding of the interaction between the water systems, climatechanges and land use is an essential need for the present world.

In Sri Lanka, evidences are sufficiently available to understand the climatechanges. It is also apparent that these changes are preliminary affecting our river basinsfrom which huge volume of water through 103 rivers are carried from uplands to thelowland. It is obvious that Sri Lanka‟s fresh water availability varies significantlyaccording to river basins and seasons. From hydro-meteorological point of view, a waterdeficit or a surplus of a river basin is basically a function of rainfall and topography ofthe upper catchment. But it is apparent, that the human interference on water in theupper catchment is a vital determinant factor of the river water flow to the lower basin.

The main objective of this paper is to discuss how a seasonal stream called MiOya upper catchment water yield is affected by rainfall variations. The effects of exitingland use on the water resources are highlighted as the main determinant factor. The totaleffect of these both impact is finally analyzed to assess the effectiveness of the river inthe use of the lower basin water needs.

Keywords: Climate change, climatic variation, upper catchment, lower catchment