基于水库旱限水位动态控制的供水策略研究

Water supply strategy based on dynamic control of drought limit water level

为了克服现行水库旱限水位确定方法和功能定位上存在的不足,更好地为水库抗旱调度提供技术支持,通过结合供水系统水文干旱识别方法,用汛末蓄水量、干旱期设计来水量及供水规则计算干旱预警期。并根据实际来水逐月修改来水系列,对当年潜在干旱期和干旱预警期进行再计算,实现旱限水位的动态控制,由此提出了用“预警期/旱限水位”数对的形式(Td,DL)来表示的旱限水位动态控制方法。将旱限水位与限制供水策略相关联,用水库旱限水位作为触发水库限制供水的特征水位。并以水库累计缺水指数最小为目标,以限制供水系数为优化变量,建立水库进入干旱预警后的供水模拟-优化模型。以天津市于桥水库为实例研究,结果表明,旱限水位动态控制方法对水库干旱的预警不仅更加合理,且具有较好的可操作性;旱限水位与限制供水策略相关联,避免了潜在干旱期内水库出现程度更加严重的缺水,对不同蓄水条件下的限制供水系数进行分析,发现限制供水系数最优值一般取在0.5~0.75。

This paper is aimed at providing a water supply strategy based on the dynamic control of the drought-period constrained water supply level. For this purpose,the paper has first of all indicated that it is necessary to point it out that here there exist 2 shortages of the current limited water storage capability due to the reservoir drought level:( 1) It ignores the reservoirs’ regulating effect and the monthly water transfer strategy;( 2) It is not associated with a clear water supply strategy. To solve such two existing shortcomings, a dynamic control method for reservoirs drought limit water level has to be proposed in the paper,and a better water supply strategy for the drought period has been established by combining the hedging rules and the drought limit water level. Seeing the need,we have first of all proposed a calculation method to evaluate the drought limit water levels by using the number pair form known as "the early warning period/drought limit water level" ( T_d,DL),and brought about its dynamic control procedure:( 1) Simulating the variation mode of the reservoir water level according to reservoir storage at the end of flood season,design inflow during drought season and the water supply rules;( 2) In combination of the hydrological drought identification method with the water supply system to distinguish between the situations of the potential drought period and the wet period to set the early drought warning period;( 3) Working out the corresponding drought limit water levels;( 4) Modifying the monthly inflow situation standard according to the actual inflow variation,and,then,checking and recalculating the inflow situation potential drought period and the early drought warning period correspondingly. And,we have been managing to integrate the drought limit water level and hedging rules,so as to make the drought limit water level of the reservoir into a specifically controlled level for starting the hedging rule. Thus,taking the minimally accumulative water shortage index as the objective and the hedging factor as the optimistic variable,we have been successful in establishing a model of water supply simulation and optimized it through the drought warming control method,and,finally,successfully applying it to the Yuqiao Reservoir,Tianjin.The results of our study show that the dynamic control method for the drought limit water level proves reasonable,rational,and practical for actual operation. The combination of the drought limit water level with the hedging rules help to prevent from the severe drought events from time to time during the potential dry periods. Thus,the optimal value of hedging factors of the Yuqiao Reservoir has been found and determined between 0. 5 and 0. 75 due to the optimization of the hedging factor under the different water storage conditions.