Dynamic Change Characteristics And Numerical Simualation Of Groundwater Resources In Xianyang City

The continuous increase in water consumption and reduction in surface runoff have caused the over-exploitation of groundwater resources,leading to the formation of over-exploitation areas in some areas.In order to curb the further expansion of groundwater over-exploitation area,this paper takes Xianyang City as a typical area and establishes a three-dimensional visual groundwater numerical model by analyzing the dynamic change characteristics of groundwater to simulate the dynamic changes of groundwater level under different recharge conditions and mining conditions,and simulate The dynamic changes of groundwater in the region in the near term(2025)and mid-to-long term(2035)are predicted.The following research conclusions are obtained:(1)Revealed the dynamic change law of the groundwater level in Xianyang City during and between the years.The results show that the groundwater level in the southern plain area of Xianyang City presents a pattern of first rising and then falling during the year,with a downward trend between the years;the groundwater level in the hilly and gully areas of the northern Loess Plateau remains basically unchanged during and inter-yearly.The trend test value Z of each typical monitoring well in the southern plain area is greater than 2.32,and it has passed the 99%significance test,indicating that the groundwater level in the area showed a significant downward trend from 1979 to 2017;the typical monitoring well groundwater level Hurst index H in the southern plain area If the values are greater than 0.5,the monitoring well groundwater level changes are continuous;the typical monitoring well groundwater level has abrupt years obtained by the MK mutation analysis method.The reason for the mutation is that the adjustment of agricultural planting structure and the rapid development of urban industry lead to a rapid increase in groundwater extraction.(2)Calculate the amount of groundwater resources in the geomorphological unit divisions of the study area.The results show that in the three-level area,the loess plateau area,terraces,and low terraces in the Weihe River Beilin?Xianyan interval,the low terraces in the Weihe North Xian-Tong interval,and the low terrace areas in the Weihe Nanxian-Tong interval,there are excessive groundwater levels during the year.Due to mining phenomenon,the deficits during the year were-42,618,300 m3,-54,673,200 m3,-52,597,400 m3,-18,521,800 m3,and-23,731,100 m3.The calculation results are converted into the administrative divisions of counties and districts(cities)by area.The maximum groundwater deficit in Qindu District is-73.18 million m3,and the minimum groundwater deficit in Jingyang County is-40,424,400 m 3.In 2015,the "Shaanxi Water Resources Bulletin" divided Xianyang's over-exploitation areas basically the same.(3)Established and verified a three-dimensional groundwater numerical model in the study area.The results show that the root mean square error between the simulated and measured groundwater levels of typical monitoring wells in Xianyang City is between 0.225 and 0.850,and the correlation coefficient is between 0.780 and 0.940.The two are in good agreement,indicating that the model It can be used to simulate the groundwater level in the study area.The influence of the aquifer permeability coefficient K,water supply ? and rainfall infiltration coefficient n on the simulation results of the model is analyzed.The results show that the rainfall infiltration coefficient n is the most sensitive to the groundwater level simulation results,followed by the water supply ?,and the permeability coefficient K is the least sensitive.(4)The simulation and prediction of the groundwater dynamic change process in the study area in the near and middle and long term.The results show that under the conditions of medium and dry years in Option 1,the groundwater level in the southern part of Xianyang City has shown a downward trend in the near and medium-term,the groundwater level in the central region has increased year by year,and the groundwater level in the northern region has shown an overall upward trend in the medium and long term.Considering the second mid-year condition of the second scheme after the water supply from the Han to the Weihe River,the groundwater level in the study area generally shows a trend of first decline and then rise.The groundwater restoration effect in the southern region is better,and the groundwater level will basically be restored to the initial simulated water level by 2035.The groundwater levels of some typical monitoring wells have increased compared with the initial simulation period;the groundwater levels of monitoring wells under dry years are basically the same as those in the middle years,but due to the decrease in rainfall replenishment in dry years,the groundwater levels of some monitoring wells have shown a certain continuous downward trend.The research results provide references for water resources management in Xianyang City.