新疆孔雀河流域地下水演化及其生态效应

Groundwater evolution and ecological effect in the Kongque River Basin,Xinjiang

近50 a,西北干旱内陆河流域经历了历史时期的水土资源过度开发和近期的生态保护修复的不同阶段,对区域地下水和生态环境产生了重要影响,但地下水长期演化规律及其生态效应认识尚不清晰。以新疆孔雀河流域为典型研究区,基于最新地下水监测数据与历史数据对比,分析流域地下水流场时空演化规律以及流域地下水对河岸带胡杨林的影响作用,探讨地下水长期演化的生态效应。结果表明:1971—2021年,孔雀河流域因过量集中开采地下水引起区域地下水流动系统发生根本性变化,地下水水位整体呈下降趋势,流域内累计降幅大于40 m的面积达204.69 km^(2),累计降幅20~40 m的面积为1735.81 km^(2),累计降幅5~20 m的面积为1018.56 km^(2),并形成地下水降落漏斗;生态输水前,中下游河道长时间断流,河岸带地下水水位埋深累计降幅超过10 m,导致河岸带胡杨林退化萎缩,2016年实施生态输水工程以后,埋深逐渐上升2~4 m,上升至胡杨林生长临界水位以上,2014—2018年天然胡杨林植被覆盖率增大17%。本研究有助于认识西北干旱内陆河流域地下水和生态环境演化规律,为类似区域地下水可持续开发利用与生态保护提供科学参考。

The arid inland river basins in northwestern China have been experienced various stages of soil and water resources over-exploitation over the past 50 years,as well as ecological protection and restoration in recent years,which has significantly influenced the regional groundwater and ecological environment.However,the long-term evolution of groundwater and its ecological effects remain unclear.In this study,the Kongque River Basin is chosen as a study area,and the spatio-temporal evolution of groundwater flow field is analyzed based on the comparison of recent groundwater monitoring data and historical data.The ecological effects of long-term groundwater evolution are discussed by analyzing the influence of regional groundwater to Populus euphratica in the riparian zone.The results show that from 1971 to 2021,the groundwater flow in the Kongque River Basin has undergone drastic variation due to excessive groundwater exploitation,and the groundwater levels have shown a general downward trend.The total area where the groundwater levels have decreased by more than 40 m is 204.69 km^(2),as well as 1735.81 and 1018.56 km^(2) for 20−40 and 5−20 m,and eventually led to the formation of a regional drawdown funnel,which have seriously affected the water consumption of Populus euphratica in the middle and lower reaches.From 1971 to 2016,the regional groundwater level depth in the riparian zone of the Kongque River Basin decreased by more than 10 m,with a degradation and shrinkage of Populus euphratica.After the implementation of the ecological water transport project since 2016,the groundwater level depth has gradually increased by 2−4 m,and reached the critical groundwater level of Populus euphratica.From 2014 to 2018,the regional NDVI increased by 17%,which indicates that the coverage rate of natural vegetation has improved.This study can improve the understanding of evolution patterns in groundwater and ecological environment in arid inland river basins of the northwestern China,and provide scientific references for sustainable development and utilization of groundwater and ecological protection in similar regions.