Study On Water Supply Operation Rules For Reservoir System Based On Ending Storage Target

Reservoir operating policy plays an important role in water resources planning and management. With frequent occurrence of extreme weather and climate events, such as frequent heavy rains and droughts, water resource is changing more and more significantly, posing challenges to water resources management. Thus, it is necessary to propose more appropriate system analysis theories and practical operation rules for water-supply reservoirs. In view of that, this study proposes novel water supply operation rules based on ending storage target in the current period, from the aspects of theory analysis and practical application, to improve the efficiency of reservoir operated to supply water. The proposed operation rules consist of the release rule and water supply task distribution rule. The dissertation comprises three parts:Firstly, in order to perform well in balancing the benefits of a release during the current period versus those of carryover storage during future droughts, a new analytical hedging rule based on a double triggering mechanism is derived using Karush-Kuhn-Tucker conditions. Based on two triggers, hedging is initiated with three different hedging sub-rules through a two-step approach. In the first step, the sub-rule is triggered based on the relationship between the initial reservoir storage level and the level of the target rule curve or the firm rule curve at the end of the current period. This step is mainly concerned with increasing the water level or not in the current period. Hedging is then triggered under the sub-rule based on current water availability in the second step, in which the trigger implicitly considers both initial and ending reservoir storage levels in the current period. A single reservoir in central China is employed as a case study to analyze the effects of the proposed operation rule. Based on the three hedging sub-rules with two triggers for rationing supply, the reservoir operation performance metrics, such as modified shortage index (MSI) and maximum one-month shortage ratio (MSR) are significantly improved relative to the performance metrics of the commonly used single rules based only on the initial storage or water availability. Moreover, the proposed rule with step-wise hedging can balance the reliability of the water supply and the magnitude of the deficits during droughts. Consequently, the proposed rule exhibits the highest water supply reliability and lowest MSR in the worst drought year.Secondly, a new storage allocation rule with six different allocation sub-rules are established for the operation of parallel reservoir system with joint demand to improve the limitations of the traditional methods. For this purpose, the different piecewise linear storage-allocation rules are derived and the trigger for allocation sub-rules is given. Analyzing the piecewise storage-allocation rule, the control condition on the number of piecewise linear segments are defined to decide whether to implement the joint water supply. Moreover, the control condition on the slope of linear segment in the sub-rule is specified to determine the priority for the water supply operation of individual reservoir. A real-world parallel reservoir system in Liaoning province of northeast China-Biliu River reservoir and Yingna River reservoir is selected as a case study. Compared to the performance of the commonly used storage-allocation rules, some advantages of the proposed rule are illustrated. Most notably, lower MSI obtained, less average annual water spilled and more average annual water supplied, indicate that the storage allocation under the new rule is more reasonbale.Thirdly, a new water-supply operation rule based on the ending storage target for the complex multi-reservoir system, consisting of the release rule and water supply task distribution rule, is proposed to solve the pactical operation problems characterized in terms of multipurpose water supply and complex reservoir system topology. The release rule in proposed operation policies for complex multi-reservoir system is specified via a weighted rationing factor for water supply based on the relationship between the initial and ending storage and target storage in the current period, defined as the summation of beginning-of-period weighted rationing factor and ending-of-period rationing factor. An algorithm for obtaining the release rule is developed. Water supply task distribution rules for multi-reservoirs in series and in parallel are derived analytically based on the water level balance among individual reservoirs at the end of current period. Following that, the priority for the water supply operation of individual reservoir is investigated. Moreover, an algorithm for applying the derived water-spply distribution rule is devised. Guanyinge-Shenwo-Tanghe multi-reservoir system is studied as an example. The numerical results show that the MSI and average shortage ratio of the proposed release rule are obviously superior to those of the conventional rule curves, and the derived water supply task distribution rules are more reasonable and effective than the parametric rule.This dissertation extended the theory of water-supply operation based only on the initial storage or water availability, derived the triggering mechanism for hedging sub-rules and analytical expression for the release rule of water-supply reservoir, established storage allocation rule of water-supply reservoirs in parallel consisting of different allocation sub-rules, proposed a weighted rationing factor for water supply, developed the algorithms for solving the operation rule for complex water supply multi-reservoirs based on the ending storage target in the current period. The work has a positive meaning, not only in advancing theory analysis of optimal operation of water-supply reservoirs, but also in improvement of practical operation of large hydraulic projects.