Optimal water allocation for the transboundary Subernarekha River, India

This paper presents a linear programming model for optimal water allocations in a large river basin system. The model is applied to the transboundary Subernarekha River in India, which has two main stream reservoirs, two barrages, and three small command area reservoirs. The Tripartite Agreement (TPA) among the cobasin riparian states for sharing of its waters is analyzed. The main objective is to find the maximum annual benefits from irrigation and hydropower subject to various constraints on the system. Design constraints as per the TPA relating to the water shares among riparian states (i.e., Bihar, Orissa, and West Bengal) at individual dams and barrages are also considered. Optimal water allocations are obtained based on the 75% water year dependable flow as specified in the TPA. Water shortage and water surplus years have also been considered to determine optimal water allocations during the dry and wet years, respectively. The stream reservoirs Chandil and Icha would fail to meet the water demands during the low flow years, whereas the Kharkai and Galudih barrages would essentially satisfy water demands according to the TPA provisions. Results indicate that Bihar is likely to benefit most from the TPA.