Changes Of Groundwater Environment And Delineation Of Water Source Protection Areas In Plain Area Of Jingbian County

Water resources is not only the material basis for our survival,but also an important ecological and environmental factor.The groundwater environment is an important part of the water environment,which changes often affect the natural balance of a regional ecosystem.Jingbian County is located in arid and semi-arid areas of northwestern China,where surface water resources are scarce.Groundwater resources are the main source of drinking water for residents in the plains.However,with the acceleration of the process of urbanization in Jingbian County,the construction scope of the county has been extended to source water protection area,so that the groundwater environment of the water source has been destroyed,and a series of groundwater environmental problems have emerged,which have caused a great threat to the drinking water safety of the residents.At present,there are few reports and literatures on the multi-year change trend of groundwater environment in the plain area of Jingbian County.In this paper,in order to reveal the direction and influence factors of groundwater environment change,the changes of groundwater environment in both temporal and spatial dimensions are deeply studied from the aspects of dynamic variation of groundwater level and hydrochemical characteristics and its evolution law.On this basis,it is of great significance for the sustainable development of Jingbian County to put forward a rational suggestion for the division of source water protection area,to promote the protection of groundwater environment in the plain area of Jingbian County,and to develop groundwater resources in harmony with socio-economic development.The plain area of Jingbian County is taken as the research object in this paper.Based on extensive inspection of relevant materials and literature,the following results are obtained through field survey,field test,data analysis,hydrogeochemical method and numerical simulation:?1?The annual variation of groundwater level in the region has obvious seasonal periodicity,and the groundwater level has shown a downward trend for many years.A certain scale of groundwater depression has been formed in the water source area of Siboshu and Yidangwan area,indicating that the groundwater in the area is negative all the year round.In the negative equilibrium state,the groundwater environment is gradually deteriorating.?2?In the regional distribution,the main ion content in groundwater decreases from south to north along the direction of runoff,and increases from west to east.In time,the concentration of TDS and most ions in groundwater increases.The growth of NO₃^-concentration is particularly obvious;?3?Piper's three-line diagram shows that calcium bicarbonate water is distributed in the central plain area and the northern desert area,and the mixed water is distributed in the junction area between the plain area and the desert area.The transition zone between loess slope and plain and the Yangjiawan area are mainly distributed with sodium chloride type.The hydroehemical maps of groundwate shows that the variation of hydrochemical type of groundwater in the middle and northern part of the desert beach area is small,and that in the southern part of the area is greater than that in the north part.The dominant cations Mg²⁺in the south follow the rules of Na⁺?Na⁺?Mg²⁺,and the proportion of Cl^-and SO₄^2-in the anions increases year by year.The water chemistry of confined groundwater has the same trend as that of unconfined groundwater,but the variation of confined groundwater is relatively small,and most of the changes occur in artificial mining areas.?4?The groundwater in the study area has dissolved carbonate dissolved in rock salt,dolomite and calcite,dissolved in sulphate such as gypsum,dissolved in fluorite,etc.,and in the process of groundwater runoff,the positive and inverse processes are accompanied by the cation exchange and adsorption.The occurrence of groundwater chemistry in individual areas is also controlled by evaporation and precipitation.?5?The quality of confined groundwater in the area is better than that of unconfined groundwater,but both show a deteriorating trend.With the expansion of Jingbian County,the groundwater in the Guojiamiao area of the Siboshu water source has been polluted.In addition,the increase in agricultural activities has led to the increasing pollution of NO₃^-in groundwater in protected areas,which has threatened the safety of drinking water for urban residents.?6?In order to protect the groundwater environment and ensure the safe supply of drinking water sources,Source water protection area will be redefined for the water source of the Siboshu and the Xixinqu.According to the calculation results,the area of the first-grade protection area of Siboshu water source area is reduced from 0.43km² to 0.17km²,and the area of the first-grade protection zone of Xixinqu is 0.20km²,the area of the second-grade protection zone of Siboshu water source area is adjusted from 60.93 km² to 21.01 km².The area of the secondary protection area of the water source area in Xixinqu is 21.53 km²,the area of the quasi-protection area is adjusted from 76.41 km² to 105.27 km².