永定河生态补水的地下水位动态响应

Response of groundwater regime to ecological water replenishment of the Yongding River

永定河流域生态修复是京津冀协同发展的重要议题,地下水位对生态补水动态响应的研究是关键的科学问题。以2020年春季永定河生态补水实践为研究基础,采用地下水均衡分析、相关分析和聚类分析等多种技术手段,详细讨论了不同河段河道渗漏损失、地下水动态变化与控制因素。研究发现,2020年春季大流量生态补水河道的渗漏损失率(20%~40%)比2016年(30%~60%)和2019年(41%~58%)的小流量生态补水低;生态补水条件下,77眼观测井地下水动态呈现显著回升、变化不显著和持续下降三种变化规律;根据影响因素划定了河道渗漏补给主控型、河道渗漏和降水主控型、河道渗漏-降水-地下水开采作用明显型、河道渗漏-降水-地下水开采作用不明显型4种类型。其中,河道渗漏主控型的监测井在补水期的地下水位迅速升高,升幅一般在1~19 m之间,最大达20 m,而且存在明显的滞后性。这些规律可为制定科学的生态补水方案提供技术参考。

Ecological restoration of the Yongding River Basin is an important issue in the Coordinated Development of Beijing-Tianjin-Hebei Region,and the study of the response of groundwater regime to ecological water replenishment is one of key scientific issues.In this paper,based on the practice of ecological water replenishment of the Yongding River in 2020,multiple methods,including water balance analysis,correlation analysis and cluster analysis,are employed to analyze the loss rate of the river for different reaches,patterns of groundwater level changes and the controlling factors in detail.It is found that the river leakage loss rate(20%~40%)with large-flow ecological water replenishment in 2020 is lower than those with small-flow replenishment in 2016(30%~60%)and 2019(41%~58%).At the same time,under the condition of ecological water replenishment,the groundwater dynamics of 77 observation wells in the study area showed the patterns with three types,which are the type of significant recovery,the type of no significant change and the type of continuous decline.According to the controlling factors,four types of groundwater changes are classified,which are the type of river leakage recharge,the type of river leakage recharge and precipitation,the type of distinct impacts under the controlling factors,and the type of unobvious impacts under the controlling factors.The groundwater level under the type of river leakage recharge gets rise rapidly,and the general increased water level is 1~19 m with the maximum of about 20 m.Meanwhile,obvious delay in the groundwater levels in monitoring wells with responses to leakage are also demonstrated.These findings may provide technical references for the formulation of scientific ecological water replenishment scheme.