Delineation of Locations for Water Storage Systems Using Future Precipitation Data – A Case Study of Sri Lanka

Abstract

Paying less attention to the expected precipitation changes when implementing new water-related projects, does not seem supportive in mitigating water crisis arising from climatic changes. Sri Lanka is a country possessing a large number of water storage systems compared to its extent and population. Besides, the year-round rainfall delivers a considerable water input throughout the year. Yet, the country reports frequent water scarcities as a result of spatial and temporal variations in rainfall patterns. In addition, irregular distribution of water storage systems and accumulation of water withdrawal have been identified as the main reasons for the current water crisis. When observing the predicted changes in the precipitation pattern, this issue is expected to accelerate in the future. In order to tackle the issue, this particular study proposes to consider the future precipitation prediction data in delineating locations for new water storage projects in the country. The preliminary selection of locations was carried out considering the widely used data types. Thresholds and weighted linear combination methods were utilized in prioritizing the related conditions at the primary location selection. Pairwise comparison method was utilized in assigning the weights. These locations were then filtered by the favorable locations based on the present and future precipitation data. The result of the study reveals that the districts of Colombo, Kalutara, Gampaha and Galle located within the wet zone should be prioritized in large scale water storage projects. The study further reveals that the dry zone can self-sustain with the available water storages. It also points out that 96% of the existing tanks in the country will be dried out mainly due to the reduction of water input and over exploitation in the future.