Study On The Dual Control Of Water Quantity And Groundwater Level In Hohhot Urban Planning Area Based On Numerical Simulation

Groundwater is the main source of water supply in Hohhot.As the urban planning area of Hohhot City expands to the south,the utilization and development of groundwater resources has entered a new stage,in order to balance the contradiction between the limited amount of exploitable groundwater resources and the urgent demand for groundwater resources to ensure sustainable development,it is necessary to analyze and evaluate regional groundwater resources and the current exploitation level,and determine reasonable and feasible groundwater control indexes.Based on the analysis and summary of previous geological and hydrogeological achievements and related data,established the three-layer heterogeneous hydrogeological conceptual model of Hohhot urban planning area.Based the hydrogeological conceptual model,a numerical simulation model of unstructured long time series groundwater flow in Hohhot urban planning area from 2009to 2020 was established by using GMS+UGIRD.For model identification and validation,using the trial and error correction method to compare the model calculation results with the measured flow field in the study area,the simulated flow field and water level process line fit well.The simulation results show that the average total replenishment in the simulation area from 2010 to2020 is 4.011×10~8m~3/a,the total excretion is 4.958×10~8m~3/a,the equilibrium difference is-0.947×10~8m~3/a,and the overall situation is under negative condition.Lateral supply and precipitation infiltration are the two main recharge sources,accounting for 47.23%and 27.75%of the total recharge,respectively.Groundwater exploitations is the main discharge item,accounting for 85.25%of the total discharge,the agricultural mining accounted for 63.63%and urban mining for 21.62%.Based on the numerical model,this study calculated and evaluated the amount of mining resources in the study area.The total amount of mining resources in each township in the study area was 42404.76×10~4m~3,among which the amount of mining resources in shallow area was19895.70×10~4m~3,and the amount of mining resources in single area and deep area was 22,509.05×10~4m~3;according to the analysis and evaluation of the mining degree based on the current mining amount,the shallow overmining areas are concentrated in the towns of Tumet Left Banner,Tuoketuo County and Helinger County,while the single and deep overmining areas are mainly concentrated in the urban concentrated water supply mining areas.According to the analysis results,a reasonable development and utilization plan is formulated.The groundwater level and water volume changes in the next 5 years under pressure extraction conditions are predicted,and the results show that:after the achievable pressure extraction,compared with 2020,the aquifer storage capacity will increase by 0.54×10~8m~3/a,both the phreatic water level and the confined water level have a certain degree of recovery at the pressure mining site,and the entire simulation area has basically reached a state of dynamic equilibrium.Based on the exploitation and utilization plan,the corresponding groundwater dual control management index is proposed.Under the wet year and normal water year,the water volume control index is set to 4.13×10~8m~3,and the dry year water volume control index is set to4.75×10~8m~3.The corresponding water level control indexes are put forward based on the water quantity indexes,which are 1036.5m for shallow groundwater and 1036.0m for deep groundwater in wet and normal years,1035.2m for shallow groundwater and 1035.0m for deep groundwater in dry years.