Research on Joint Water Supply Optimal Operation Rules for Multi-reservoir System under a Mixed Water Allocation Scheme

The joint water supply operation rule for the multi-reservoir system plays a critical role in mitigating drought-induced water scarcity risks. Within an aggregation-decomposition framework, the rule can be equated to the operation rules of an aggregated equivalent reservoir and the method for allocating shared water supply tasks. The allocation method for shared supply tasks, which significantly influences both the spatial-temporal distribution of water resources and the realization of compensatory effects among reservoirs, constitutes a key and complex challenge in joint operation. The dynamic water allocation ratio method overlooks storage compensation between reservoirs and can lead to wasteful spillage, and the compensation regulation method may jeopardize supply for a reservoir's own users due to over-compensation. To address the limitations of traditional methods, this paper proposes a hybrid water allocation scheme that integrates both dynamic water allocation ratios and compensation regulation. A joint optimal drought-resistant operation model for the reservoir system is developed using a parameterization-simulation-optimization modeling framework, with dimensionality reduction achieved. Application to the joint water supply system of the Qingshanzui and Jiulongdian reservoirs in Chuxiong Prefecture, Yunnan Province, demonstrates that: under the guidance of the proposed rule, proactive water supply restriction in the early stages of consecutive dry years prevents severe water shortages for high-priority users. Compared to the dynamic water allocation ratio method, the proposed hybrid scheme, by leveraging inter-reservoir compensation, reduces spillage by 8.15 million cubic meters during consecutive dry years and lowers the maximum agricultural water shortage rate by 1.6% over long-term operation. The proposed joint water supply operation rules are scientifically sound and provide technical support for water authorities in guiding reservoir system operation for drought mitigation and disaster reduction.