南水北调地下水回补对潮白河冲洪积扇中上部地表形变响应及控制因素

Response and contral factors of surface deformation in the middle and upper regions of the Chaobai River alluvial fan for the groundwater recharge of South——North Water Diversion Project

2014年南水进京后,持续开展地下水回补对于遏制和减缓地面沉降发展起到重要作用,但地下水回升由此带来的不同区域、不同层位的地面沉降与回弹机制及其控制因素尚不明确。深入探讨和研究回补时间、回补量、回补地点与水位及地表形变之间的关系,了解地表形变发生机理和识别主控因素,为后续如何科学回补,发挥最大化水资源回补效益、对地面沉降防治和超采区治理具有极其重要意义。笔者以潮白河冲洪积扇中上部区域为例,采用永久散射体差分干涉测量(PS-InSAR)技术获取研究区地面沉降形变信息,并结合区域分层地下水位动态变化、分层沉降变化等多手段进行耦合,查明研究区地表形变与多因素之间的响应与控制因素。结果表明:南水持续回补导致区域地面沉降减缓,并在牛栏山地区出现地表抬升,抬升范围也随着水位上升逐渐向中下游扩展,2022年最大回弹速率达46.9 mm/a;地表形变具有明显的受断裂所控制的第四系沉积差异特性,以黄庄—高丽营断裂、顺义断裂和南口—孙河断裂所分割的后沙峪凹陷范围内变化明显大于其他地区;地下水位变幅与富水性差异决定水位上升范围与响应变化,而沉积构造作用所造成第四系沉积差异在地下水流向上具有一定控制作用。结果为地面沉降防控和机理研究提供理论和科学依据,同时也为后续开展地下水科学回补和方案优化提供指导和借鉴。

Objectives:Since the South-to-North Water Diversion Project Central Route was first operated in December,2014,continuous groundwater recharge makes great contribute to preventing and slowing down the development of land subsidence.However,the influencing factors and the mechanism of land rebound response to the groundwater rise are not yet clear.In-depth exploration and study of the relationship between recharge time,recharge volume,recharge location and water level and land deformation,understanding the mechanism of land deformation,and identifying the primary factors,is of great significance for the follow-up of how to recharge scientifically,maximize the benefits of water recharge,and prevent and control land subsidence and the management of overexploitation areas.Methods:This paper takes the middle and upper area of Chaobai River alluvial fan as an example,adopts permanent scatterer differential interferometry(PS-InSAR)technology to obtain the information of land deformation,and coupling with the multi-groundwater monitoring well and extensormeters and other means of,to find out the response and controlling factors of the ground surface deformation in the study area and the multi-factors.Results:The findings indicate that(1)the region's land subsidence is slowed down by the south water's constant replenishment,and that the Niulan Mountain region experiences surface uplift.With the rise in water level,the uplift area also gradually widens to the middle and downstream,and the maximum rebound rate reaches 46.9 mm/a in 2022.Conclusions:The Houshayu depression,which is split by the Huangzhuang-Gorliying fault,Shunyi fault,and Nankou-Sunhe fault,has undergone more alterations than other regions because for any particular characteristics of Quaternary depositional differences governed by faults;The range and responsiveness of water level rise are determined by variability in groundwater level amplitude and water richness,and the direction of groundwater flow is somewhat controlled by quaternary sedimentary differences brought on by sedimentary tectonics.