Reservoir operation and evaluation of downstream flow augmentation

Operation of a storage-based reservoir modifies the downstream flow usually to a value higher than that of natural flow in dry season. This could be i mportant for irrigation, water supply, or power production as it is like an additional downstream benefit without any additional investment. This stud y addresses the operation of two proposed reservoirs and the downstream flo w augmentation at an irrigation project located at the outlet of the Gandak i River basin in Nepal. The optimal operating policies of the reservoirs we re determined using a Stochastic Dynamic Programming (SDP) model considerin g the maximization of power production. The modified flows downstream of th e reservoirs were simulated by a simulation model using the optimal operati ng policy (for power maximization) and a synthetic long-term inflow series. Comparing the existing flow (flow in river without reservoir operation) an d the modified flow (flow after reservoir operation) at the irrigation proj ect, the additional amount of flow was calculated. The reliability analysis indicated that the supply of irrigation could be increased by 25 to 100 pe rcent of the existing supply over the dry season (January to April) with a reliability of more than 80 percent.