| Kongqi River Irrigation District is located at the southern foot of Tianshan Mountain in Xinjiang and the northern margin of Tarim Basin.The evaporation is strong and the precipitation is scarce in the study area,which is a typical area of "no irrigation,no agriculture".In the past two decades,the scale of agricultural water use has expanded rapidly.On the basis of surface water irrigation,a large number of groundwater has been exploited for irrigation,which has caused environmental geological problems such as regional groundwater level decline,groundwater salinization and so on.It is of great practical significance for realizing the sustainable utilization of groundwater resources and the sustainable development of regional economy to study the temporal and spatial variation law of groundwater in Kongqi River Irrigation District by scientific means,and to simulate and predict the groundwater dynamics.By collecting the data of meteorological geography,geology,hydrogeology,development and utilization of water resources in the study area,and combining with the recent field investigation data,this paper analyzes and studies the water resources and hydrogeological conditions of the Kongqi River Basin,and puts forward the conceptual model of groundwater circulation in the study area.On this basis,the MODFLOW simulation model of Kongqi River Irrigation District is established by using GMS software.The aquifer is divided into three layers vertically and a square unit of 500 m horizontally,and the source and sink terms of groundwater circulation and aquifer parameters are divided into regions to form a numerical model to simulate the groundwater flow field in Kongqi River Irrigation District.Through the groundwater flow simulation of Kongqi River Irrigation District in various scenarios,the following achievements and understandings have been obtained:(1)Based on the assumption of steady flow,the groundwater flow field in 1971 and 2019 is simulated,and the main parameters of the model are corrected and determined.The simulation results represent the groundwater circulation model under the conditions of approximate natural state(1971)and present condition(2019).It reflects the variation characteristics of groundwater flow field in recent 50 years,and the maximum drop depth of groundwater funnel is more than39 m.(2)The recharge condition of groundwater in Kongqi River Irrigation District has been basically unchanged in the past 50 years,and river leakage is the main source of recharge.However,the situation of groundwater discharge has changed significantly.In the approximate natural state,phreatic evaporation is the main way of groundwater discharge,accounting for86.21% of the total discharge.Under the current conditions,artificial exploitation has become the main mode of discharge of groundwater,accounting for 69.29% of the total discharge,while the proportion of phreatic evaporation has been reduced to 29.53%.(3)Based on the periodic unsteady flow hypothesis,the seasonal dynamics of groundwater in 1971 and 2019 are simulated,the storage parameters of aquifers are corrected,and the sensitivity analysis of parameters is carried out.It is found that the sensitivity of groundwater dynamics to permeability coefficient is generally higher than that to water supply and water storage,and the influence of the overall decrease and increase of parameters on groundwater dynamics is not symmetrical.The seasonal fluctuation range of groundwater in 2019 is generally greater than that in 1971.(4)The scenario simulation analysis of the interannual change of 30 years is carried out,and the results show that if the present situation is maintained,the groundwater level will continue to decline,and when the total exploitation of groundwater is 30%,50%,the groundwater level can be restored to a certain extent.With 50% pressure mining and keeping the status quo and other conditions unchanged,it is predicted that the groundwater level can be basically restored within15 years.The above study can provide a reference basis for the management of groundwater resources in the Kongqi River Basin. |
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