Analysis On The Variation Of Groundwater Environment In The Downstream Of Fenhe River Basin,Eastern Chinese Loess Plateau

In recent years,irrational utilization and excessive exploitation of groundwater have made the groundwater environment problems increasingly prominent,which not only affect the regional ecological environment,but also become one of the restricting factors of regional economic development.In this paper,Linfen Basin in the lower reaches of Fenhe River is selected as the research area.Based on the monitoring data of groundwater depth for many years,the spatio-temporal variation of groundwater depth in this area and its controlling factors are systematically analyzed.The groundwater quality is evaluated and analyzed by fuzzy comprehensive evaluation method.(1)The groundwater depth in the study area showed an overall upward trend from 2007 to 2018;The groundwater depth in different regions is significantly different,showing a trend of high in the east and low in the west.In addition to Huozhou and Quwo counties,the groundwater depth in all districts and counties showed an upward trend,among which Yaodu and Xiangfen showed obvious over-exploitation.(2)The groundwater depth fluctuated significantly after 2010,and the amplitude of each district was significantly higher than that before2010.(3)The groundwater depth shows an increasing trend from north to south on the annual scale,and the variation range of groundwater depth is the largest in spring,and the groundwater depth is mainly reduced.Spatially,the shallow groundwater depth is mainly concentrated in Huozhou,Hongdong,southern Quwo and northern Yicheng,and the deepening area is mainly concentrated in Xiangfen,southwest Yaodu and northwest Houma.(4)The change of groundwater depth in the study area is sensitive to evaporation,less sensitive to rainfall and rural water use,and the population has a greater contribution to the change of groundwater depth.(5)Groundwater in the study area belongs to weak alkaline water,and the overall contents of nitrate,nitrite and metal elements in groundwater in the study area are less and have a small change.(6)The total hardness,dissolved solids and sulfate of groundwater in this area exceed the standard.The main pollutants of groundwater quality are cadmium,chromium(hexavalent),lead,arsenic and cyanide.(7)On the whole,the groundwater quality in this area is generally in grade I-II,and there is no class IV and V water.Type II water has the widest distribution range.Type I water is distributed in the southwest of Huozhou;The type III water is mainly distributed in the eastern part of Yicheng.This study provides important theoretical support for rational utilization and protection of water resources in the lower reaches of Fenhe River,and is of great significance for sustainable development and rational utilization of water resources.