Water Allocation Challenges in Rural River Basins: A Case Study from the Walawe River Basin,Sri Lanka

• Main Author: Weragala, D. K. Neelanga
• Format: Others
• Published: DigitalCommons@USU 2010
• Subjects: river basin; Sri Lanka; Walawe river; water allocation; watershed modeling; water resource management; Civil Engineering
• Online Access: https://digitalcommons.usu.edu/etd/589; https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1585&context=etd

This dissertation evaluates the water allocation challenges in the rural river basins of the developing world, where demands are growing and the supply is limited. While many of these basins have yet to reach the state of closure, their water users are already experiencing water shortages. Agricultural crop production in rural river basins of the developing world plays a major role in ensuring food security. However, irrigation as the major water consumer in these basins has low water use efficiency. As water scarcity grows, the need to maximize economic gains by reallocating water to more efficient uses becomes important. Water allocation decisions must be made considering the social economic and environmental conditions of the developing world. The purpose of this dissertation is to identify water allocation strategies that satisfy the above conditions, in the example of the Walawe River basin in Sri Lanka. In this dissertation three manuscripts are presented. The first manuscript takes a broad view of the current water allocation situation. The second manuscript develops a methodology to analyze water allocation under a priority-based approach with the use of network flow simulation techniques. The third manuscript analyzes the water supply-demand situation in the basin under future climatic conditions. The major findings of this study suggest that: (1) while up to 44% of water is still available for use, seasonality of inflows, poor water management, physical infrastructure deficiencies, and other socio-economic factors contribute to the irrigation deficits in the Walawe basin; (2) prioritizing irrigation over hydropower generation increases supply reliability by 21% in the Walawe irrigation system IRR 1. The corresponding annual loss in power output in less than 0.5%. Prioritizing the left bank irrigation area in system IRR 2 increases the economic gains from crop yields by US $1 million annually; (3) an increase of water use efficiency between 30-50% in agriculture can mitigate all water deficits in agriculture, urban water supply and industrial sectors; (4) the predicted 25% increase of rainfall over the Walawe basin in the 2050's allows for 43% increase in hydropower generation (with changes to power generation mode) and 3-16 % reduction in irrigation requirements; (5) network flow simulation techniques can be successfully used to evaluate different demand management strategies and improvements to the priority-based water allocation method.