Synergetic Optimal Operation of Cascade Reservoirs in Mainstream of Yellow River Responding to Drought

Cascade reservoirs are playing an important role in dealing with droughts, whereas the space-time coordination and process optimization of cascade reservoirs are difficult to realize. In this study, a multi-spatial-temporal scales synergetic optimal operation model of cascade reservoirs is built to control total water shortage in the basin and optimize the spatial and temporal distribution of water shortage by exploiting storage compensation and hydrology compensation of cascade reservoirs. Multi objective optimization is transferred into single-objective optimization with the application of penalty function. Improved nested particle swarm optimization (PSO) algorithm is used to solve the model. In the outer layer, importance parameters of regions and periods are set to realize the optimal control of drought limit water level for multi-year regulating storage reservoir. In the inner layer, the water storage and discharge rules and processes are optimized to realize the inter-annual regulation, intra-annual optimization, cascade reservoirs' synergy and spatial coordination. The model developed in this study is applied to the cascade reservoirs in the mainstream of the Yellow River, optimizing drought limit water levels of the Longyangxia Reservoir and water discharge processes of reservoirs from 2012-2014. The results show that droughts and low water periods in the Yellow River Basin can be dealt with orderly and water shortage ratios of each year are controlled between 4.9%-5.7%. The model developed in this study can improve the water resources scheduling capacity dramatically in the Yellow River Basin for better coping mechanisms of droughts. (C) 2019 The Authors. Published by Elsevier Ltd.