Author(s): C. Samarasuriya Patabendige; S. Kazama; D. Komori
Linked Author(s): So Kazama
Keywords: Natural runoff; Water withdrawals; Environmental water requirement; Hydrological model
Abstract: Water-related conflict often occurs during specific season on the local level, and the intensity of conflict is generally inversely related to geographic scale. Thus, we employed a seasonal water stress assessment using the newly devised Seasonal Water Stress Index (SWSI) for 49 river basins covering 85.45%of the total land area of Sri Lanka. To assess seasonal water scarcity, several models were used to integrate the availability, withdrawal and environmental water requirement by the river itself. The daily natural runoff was simulated for the period 1980–2011 at a spatial resolution of1 km x 1 km. Water withdrawals by the domestic, industrial and agricultural sectors were considered. Domestic water withdrawals were estimated using statistics on household water access. Data published by the Food and Agricultural Organization (FAO) were used for industrial water withdrawal modeling integrating a Divisional Secretariat (DS) division-scale value of output of products. The agricultural sector accounted for 93%of water withdrawals, as estimated based on the extent of the crop areas. The seasonal Environmental Water Requirement (EWR) was derived using the simulated natural runoff. Annual, precipitation seasons and agricultural seasons water stresses were computed. The results showed that severe water stress occurs during two major monsoons. Furthermore, dry zone river basins are under severe water stress during the “Yala” agricultural season. Our findings show that seasonal water stress assessments are essential for sustainable water resource management because annual water stress assessments underestimate the risk.