An Analytical Framework for Reservoir Operation With Combined Natural Inflow and Controlled Inflow.

Interbasin water transfers have been undertaken in those regions that water demand has gone beyond regional water availability. Some reservoirs in a recipient region have both natural inflow (NI) and the controlled inflow (CI) through water transfer. This study establishes a theoretical framework to analyze reservoir operation with combined NI and CI, via an optimization model to maximize the net benefit of reservoir operation, considering both deterministic and stochastic NI. Operation rules for both water transfer and reservoir release are derived from the framework. It is illustrated that the amount of CI depends on water availability to the recipient reservoir, the relationship between marginal benefit and marginal cost, the water transfer capacity, and the uncertainty level of NI. As forecast uncertainty increases, more water is transferred, and more water is left in the reservoir as carryover storage when the initial water availability (WA0) is small; however, with a certain high level of WA0 and forecast uncertainty, water transfer will be controlled to reduce the risk of water abandonment. Notably, the critical values of the forecast uncertainty that control water transfer are identified under the various WA0. The analysis is illustrated via a case study with a real‐world reservoir in northeastern China. In summary, this study derives hedging rules for water supply reservoir with combined NI and CI to mitigate the risk of both water shortage and water abandonment and provides guidelines to use NI forecasts for water transfer and reservoir release decisions. Plain Language Summary: In this paper, we established a theoretical framework to derive hedging rules for reservoir operation with combined natural inflow (NI) and controlled inflow (CI) through interbasin water transfer. It extends the existing studies on hedging rules, which only considered NI. We particularly address the complexity of CI decisions under NI uncertainty—on the one hand, CI enhances water supply reliability of the recipient reservoir; on the other hand, it can increase the risk of water waste via reservoir spill when the likelihood of a full reservoir is increased. We also addressed the critical values of the forecast uncertainty that control water transfer under the various initial water availability levels. In summary, the theoretical analysis provides guidelines to combine NI and CI to mitigate the risk of both water shortage and water abandonment and provides guidelines to use NI forecasts for water transfer and reservoir release decisions. Key Points: Hedging rules for reservoir operation with combined natural inflow and controlled inflow are derivedWe analyze the effect of forecast uncertainty and water transfer capacity on water transfer and reservoir release decisionsWe identify the uncertainty threshold of natural inflow that controls the decisions [ABSTRACT FROM AUTHOR]