西江流域压咸风险调度及其时空传递规律研究

枯水期珠江河口咸潮情势日益加重，径流不确定加剧了压咸风险，严重威胁沿线的供水安全。本文基于概率密度分布描述径流不确定性，构建了单源风险调度基本框架。以西江流域五座水库为研究对象，量化了预报误差与压咸风险的响应关系；揭示了压咸风险的时空传递规律；将压咸风险划分为3个等级；确定出各级风险越级传递的临界阈值。研究表明：随预报误差的增大，压咸风险提前且持续天数增加、风险率增大；压咸风险呈逐时段累积和从上游向下游、从支流向干流的时空传递规律；当预报误差超过±16%、±21%时，压咸风险从轻险越级至中险、中险越级至重险。研究成果对于西江流域压咸风险的调控和粤港澳大湾区的供水安全具有重要的应用价值。

Risk operation of inhibiting salt tide invasion and its space-time transmission in Xijiang watershed

As salt tide invasion in the Pearl River becomes increasingly severe in dry season, the risk of inhibiting the invasion is aggravated by uncertainty in the runoff, gravely lowering the safety of water supply across the watershed. This paper describes the uncertainty in the river runoff based on probability density distribution, and constructs a basic framework of single-source risk operation. In a case study of five reservoirs in the Xijiang watershed, we formulate a quantitative relationship of the runoff forecast error versus the systematic risk of inhibiting salt tide invasion, and reveal how the risk is transmitted in space and time. The forecast error is divided into three grades, and the threshold of each risk leapfrogging across the grades is determined. The results show that as the forecast error increases, the risk occurs earlier, the number of salt-inhibiting days and the risk value are increased. In time, the risk transfers from time to time in a cumulative way; in space, the risk transfers from upstream to downstream and from tributaries to the main stream. The risk leapfrogs from light to medium grade when the forecast error exceeds 16%, and from medium to heavy grade when it exceeds 21%. The results have significant application to risk regulation and control for the Xijiang watershed and to water supply security assessment for the Guangdong-Hong Kong-Macao Greater Bay Area.