Abstract: To maximize power generation benefit, this study explores reservoir impounding strategies adapted to extreme low-flow conditions in the case of the lower Jinsha River and the Three Gorges cascade reservoirs, and presents a new reservoir impounding scheme by combining the impounding rule of benefit maximization and the water supply requirement of the Three Gorges Reservoir. We also examine alternative reservoir impounding schemes aimed at different water allocation principles that meet the targets of reservoir stages or the control boundaries. Typical extreme low-flow scenarios are simulated numerically for operation and benefit analysis. From the results, we demonstrate a critical condition of natural inflow for full filling of the cascade reservoirs－the natural inflow is above the level at the frequency of 97% from August through early September, and above the level at the frequency of 90% from mid-September through November. Under extreme low-flow conditions, the cascade reservoirs will be able to perfectly fulfill the water supply requirement of the Three Gorges Reservoir if they adopt a certain joint water supply dispatching. In the case of a full filling impossible, their power generation benefit can be maximized by impounding preferentially those in the lower Jinsha River, such as the Baihetan Reservoir first and then the Xiluodu Reservoir as recommended by this study.

Key words: cascade reservoirs, extreme low flow, reservoir impounding strategy, water supply dispatching, power generation benefit