117-Water Balance Assessment of a River Basin through System Simulation.

Abstract

Assessment of overall water resources as well as surplus (or shortage) in a river basin considering the current and future needs is the key in water resources planning. This exercise is normally done through water balance studies which estimate annual water availability in a 75% dependable year and projected needs for different purposes. By the use of computer simulation models, the outcome of these preliminary studies can be refined by evaluating the performance reliability of a river basin system over a long period. Such studies need to take into cognizance the effect of carryover capacities and operation policies of major reservoirs in making up the water shortage or augmenting the surplus. The present paper assesses the surface water balance of Godavari basin in Peninsular India in the ultimate water development scenario. Since the interest is to assess such a balance at the terminal storage/diversion structures, multireservoir simulation has been carried out for 30 years for 2 proposed storage projects viz. Inchampalli and Polavaram at the tail end of the basin and an existing barrage at Dowlaiswaram just before the confluence of the Godavari with the Sea. A multireservoir simulation model has been used for the study. The present study envisages long term solution for integrated operation of both the reservoirs and the barrage in the basin to find out their operational reliability. Thereafter, their performances have been refined through simulation considering different priorities of use (irrigation/power) and downstream committed releases, based on which appropriate firm power and release pattern has been fixed. Finally, quantification of surplus surface water in the basin has been done according to the derived optimal reservoirs operation policy.