考虑旱灾风险的水库分级分期旱警水位内涵与确定方法

Connotation and determination method of graded and staged drought warning water level for reservoir considering drought risks

水库蓄水是重要的抗旱应急水源,设定水库旱警水位是提高水库抗旱减灾能力的重要措施。本文基于已有成果,拓展旱警水位的概念与内涵,提出了轻旱、中旱等干旱典型年Ⅰ级、Ⅱ级、Ⅲ级与Ⅳ级分级、分期旱警水位的控制原则;将水库调度模型与计算农业需水量与需水过程的AquaCrop-OSPy模型结合,以农业生产因旱损失风险最小为目标,模拟不同等级干旱典型年在不同初始水位下的水库运行过程与农业生产因旱损失风险,并绘制农业生产因旱损失风险曲线;以损失风险等级分界点所对应的水库水位为分级旱警水位;采用AquaCrop-OSPy模型模拟多种灌溉方案下各典型年的农业生产,计算各月供水率与农业减产率的偏相关系数,来表示各月的需水敏感度,以此作为时段水量对冲和旱警水位分期的依据。以东庄水库为例,选择其供水区域内的主要农作物夏玉米与冬小麦进行了实例分析。结果表明:旱警水位的分级与分期控制反映了临界调控理论与水量的时空对冲调控;农业生产因旱损失风险变化曲线呈现连续、多拐点、三阶段的变化特征,东庄水库轻旱年旱警水位为Ⅳ级预警,中旱和重旱年为Ⅳ级、Ⅲ级与Ⅱ级预警,特旱年为Ⅱ级、Ⅰ级预警,旱警水位从时间上分为7—12月、1—4月和5—6月三期。

Reservoir water storage is an important emergency water source for drought resistance,and setting the reservoir drought warning water level(DWWL)is an important measure to improve the reservoir’s drought resistance and disaster reduction capacity.Based on existing achievements,this article expands the concept and connotation of DWWL,and proposes the control principles for typical drought years such as light drought,moderate drought,etc.,which are classified into gradesⅠ,Ⅱ,Ⅲ,andⅣ,and staged DWWL.Combining the reservoir operation model with the AquaCrop-OSPy model,which calculates agricultural water demand and water demand process,and aiming to minimize the risk of agricultural production losses due to drought,the reservoir operation process and agricultural production risk of drought losses in different initial water level scenarios for typical years with different levels of drought were simulated,and the risk curves of agricultural production loss due to drought was drawn.Reservoir water level corresponding to the demarcation point of loss level risk is used as the graded DWWL.The AquaCrop-OSPy model is used to simulate agricultural production in each typical year under various irrigation schemes,and the partial correlation coefficient between monthly water supply rate and rate of reduction in agricultural production are calculated to represent the sensitivity of water demand in each month,which is used as the basis for water volume hedging and DWWL staging during time periods.Taking Dongzhuang Reservoir as an example,the main crops in its water supply area,summer maize and winter wheat,were selected for example analysis.The results show that the graded and staged control of DWWL reflected the critical regulation theory and the spatiotemporal hedging regulation of water volume;the change curve of the risk of agricultural production losses due to drought presents a continuous,multi inflection point,and three-stage change feature.DWWL of Dongzhuang Reservoir is classified as LevelⅣwarning in light drought years,LevelⅣ,Ⅲ,andⅡwarning in moderate and heavy drought years,and LevelⅠandⅡwarning in extreme drought years.DWWL is divided into three periods from July to December,January to April,and May to June in terms of time.