Author(s): H. S. Madhusan Hettiarachchi; B. M. L. Arunoda Basnayake
Linked Author(s): B.M.L.Arunoda Basnayake
Keywords: Optimization; Tank cascade system; WEAP
Abstract: Spatial and temporal variation of rainfall brings many problems to dry zone of Sri Lanka including insufficient water for cultivations in‘Yala’season from April to August and flooding in‘Maha’season from September to March. Tank based irrigation has been developed to store excess rain water during‘Maha’season and to supply the stored water for cultivation during‘Yala’season. The tanks of various sizes in the dry zone are interconnected to form tank cascade systems. The need to maximize the productive use of the limited water has been widely recognized in this area with the increasing demand for water. This study developed an optimal water management plan for the Pihimbiyagollawa tank cascade system in the dry zone of Sri Lanka using Water Evaluation and Planning (WEAP) software. Firstly, it is investigated whether it is possible to supply water demand when the tanks are operated standalone. It is found that 41%of the annual water demand could be supplied comprising 87%in the'Maha'season and 19%in the'Yala'season. Even if some tanks were spilled, that amount was not sufficient to satisfy the water demand through diversion. It has been proposed to carry water from Mahaweli River through a canal to satisfy the water requirement in the cascade. Secondly, water was allocated from the proposed canal to the tanks in the cascade. Water demand could be supplied in both seasons and results showed that annual water requirement from canal is 5.723 MCM which is less than the possible water diversion of 6.682 MCM.
Year: 2016