Groundwater Simulation In The Partial Area Of The ZhongNing Section Of The Yellow River In Ningxia Based On MIKE SHE Model

Located in the western margin of China's monsoon region,Ningxia is characterized by short heat in summer,long cold in winter,little rain in drought and intense evaporation.Due to the long-term climate drought,problems such as regional water shortages and meteorological disasters have become increasingly prominent.In order to alleviate the regional water resources shortage,it is planned to build a water source project exploration area for the Xihaigu area on the south bank of the Zhongning section of the Yellow River in Ningxia.Take water from the water source to supply water to urban and rural residents and industries within the target water supply range.Therefore,taking the Zhongning section of the Yellow River in Ningxia and its surrounding areas as the study area the Mike She model is used to simulate and analyze the hydrological process in the basin,the distribution of groundwater flow field,the hydrological response of land use and precipitation change,and to simulate and predict the dynamic change of groundwater in the next five years based on different exploitation schemes.It is of great significance to understand the hydrological cycle process in this small watershed.In this paper,the Zhongning section of the Yellow River in Ningxia and its surrounding areas are used as the research area.Based on the distributed hydrological model MIKE-SHE,the hydrological process of this small watershed in the upper reaches of the Yellow River is simulated.The parameters of the model were calibrated and verified by using the observed well water level data of the pumping test site in the research area The result of fitting the model through the measured data in the study area shows that the improved model parameter setting is reasonable,can explore the dynamic changes of the groundwater level in the study area,and has certain application value.Based on the research work of this paper,the following main achievements have been achieved:(1)Based on basic data such as topographic elevation data,soil profile types,land use patterns,stratum structure information data and meteorological data from two meteorological stations of Zhongwei(53704)and Zhongning(53705)in the surrounding area of the Zhongning section of the Yellow River in Ningxia,a distributed hydrological model for small watershed was established.The horizontal and vertical permeability coefficient,specific yield and water storage coefficient of saturated zone aquifer,soil moisture content and saturated hydraulic conductivity of unsaturated zone,channel leakage coefficient of river and lake modules,Manning coefficient M of overland flow module and other model parameters are calibrated.(2)The hydrological model established in this paper can better simulate the hydrological process in the study area,and mainly simulates the annual average groundwater level and flow field.In the process of parameter calibration and verification of the model,the measured data and simulated values of the pumping test site fit well.The regular root mean square errors of observation wells GCJ2-1,GCJ2-8,GCJ3-1,and GCJ3-6 located at 200m from the Yellow River on the south side of Binhe Road in Xuanhe Town of Zhongwei City in the study area were 0.083,0.207,0.168 and 0.099m,respectively.The model correlation coefficients were 0.856,0.950,0.935,0.982,respectively.The root mean square errors of GCJ3-1 and GCJ3-6 in the validation stage were 0.049 and 0.040m,respectively.The model correlation coefficients were 0.937 and 0.941,respectively.(3)The dynamic changes of the groundwater level in the study area are affected by meteorological conditions and the water level of the Yellow River.The closer the area is to the Yellow River,the greater the impact on the recharge of the river's water level.The groundwater level is closely related to climatic conditions such as precipitation and evaporation.The water level in the southwest of the study area is high while the water level in the east is low.The highest water level is about 1211m and the lowest water level is about 1188m.The direction of groundwater flow is from west to east,basically the same as that of the Yellow River.(4)The groundwater level changes and rainfall have an obvious synchronization relationship,and the overall trend line is in the shape of a mountain peak.Since January,with the increase of rainfall,the groundwater level has increased significantly,and reached a peak of 1201.46m in September.The rainfall peaked in August and the groundwater level peaked in September.It can be seen that the rainfall replenishes groundwater to a certain extent.Since October,as the rainfall decreases,the groundwater level decreases with the decrease in recharge.The model established in this paper uses local sensitivity analysis parameters,and the results show that the permeability coefficient of the saturated zone aquifer is the most sensitive in this model,and the Manning coefficient M has little effect on the model.(5)In the study of the response of extreme land use schemes to the water level of the watershed,the LAI gradually increased from grassland-farmland-woodland,and the annual average canopy intercepted evapotranspiration increased from 67.642mm to 254.132mm.The change of vegetation cover mode caused by land use led to different canopy interception effects.Canopy interception will reduce the recharge of rainfall to groundwater system,and the stronger the canopy interception evapotranspiration is,the lower the groundwater level will be.In order to explore the contribution of land use and precipitation change to groundwater level,five hypothetical scenarios were set.According to the results of simulation schemes,both land use and precipitation change had a certain degree of influence on groundwater level in the study area,and precipitation played a major role in influencing groundwater level change.(6)Three different exploitation schemes A,B and C are set based on the current amount of groundwater mining,the current amount of groundwater mining by 10%and 20%.Based on the data series of rainfall and evaporation from 2014 to 2018,the groundwater in the next five years is predicted and analyzed.The results show that,with the pumping well as the center,the falling funnels with different influencing radii and depths are generated under the three mining schemes,which continue to expand from scheme A to scheme C,but the dynamic variation range of the groundwater table is small and the groundwater table is relatively stable.