Development of operation policy for Tawa dam – A research report by National Institute of Hydrology

The study deals with the development of an operation policy for the Tawa dam. It adopts rule-curve based policy for conservation regulation of the dam developed for three levels viz. upper rule level, middle rule level (critical for irrigation) and lower rule level (critical for water supply and upstream use). The generated simulation model developed by the Water Resources System Group at the National Institute of Hydrology is used to simulate the system operation and to refine the rule curves.

Reservoir storage is necessary to use the highly variable water resources of a river basin for various purposes such as municipal & industrial water supply, irrigation, hydroelectric power generation and navigation. Under certain streamflows and multiobjective demands, water allocation process becomes complex.

An operating plan or release is a set of rules for determining the quantity of water to be stored or released from a reservoir or a system of several reservoirs under various conditions. The operating rules provide guidance to the water managers who make the actual release decisions. The evaluation of current operating rules of existing reservoirs is very important to meet the changing demands according to the public needs and objectives.

Simulation models are used to represent a system and to predict the behavior of the system under given set of conditions. They are limited to predicting system performance for a user specified set of variable values. Alternatively, an optimization procedure may involve iterative executions of a simulation model, with the iterations being automated to various degrees.

A number of simulation runs have been taken by adjusting the rule curves to arrive at the final rule levels for satisfying the target demand to the maximum extent possible. The current operating policy of the reservoir is also simulated and the results compared with the recommended rule curve based policy.

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