Evolution Mechanisms Of Surface-Groundwater Resources And Environment In The Zhuozhanghe Drainage Basin

The evolution mechanism of regional surface water,groundwater and water environment is a hotspot and difficulty in the study of water resources and water environment.This study focused on the low utilization rate of water resources,severe water pollution,and persistent decline in groundwater levels in the Zhuozhanghe drainage basin.Field investigation and data analyses were combined as study methods;statistical hydrology and hydrogeology were used as guide theories;and numerical simulations and coupled models techniques were used to show the evolutionary characteristics and patterns of the aquatic environment in the Zhuozhanghe drainage basin and to carry out simulation and prediction of surface and groundwater resources.The main research results are as follows:1.Evolutionary patterns of water resources.There were spatial differences in the seasonal and interannal variation in monthly average and in the contribution rates of meteorological changes and human activities to runoff.Precipitation had greater effects on runoff than evaporation did.The groundwater levels of cavern water in the Xin'an Springs exhibited varying amounts of declinein different regions,with that of the runoff stagnation and discharge zones being the largest and smallest,respectively.The seasonal and interannual variation of different types of shallow pores in Changzhi basin is different in the depth of burial.2.Water pollution status and water environmental evolution characteristics.Water pollution survey results showed that the annual discharge of wastewater was on the rise,and the concentration of COD and ammonia nitrogen was on the decline.Agricultural non-point source pollution in the Zhuozhanghe drainage basin primarily consisted of nitrogen pollution by livestock and poultry breeding(93.82%).The evolution of water environment had the characteristics of spatial and temporal differentiation.Spatially,water quality in Group A was better than that in Group B.The year was divided into Stages I(January–March)and II(April–December).Water quality in Stage II was better than that in Stage I.Serial annual water quality was grouped into three categories,namely Category A(2000–2004),Category B(1990–1992),and Category C(2005–2013).Water quality in Category A gradually deteriorated.Category B had better water quality.Water quality in Category C gradually improved and stabilized.3.Surface water simulation.The result of discretization of the drainage basin showed that the optimal sub-basin number of SWAT simulation was 79.The main parameters affecting runoff were the runoff curve coefficient,maximum canopy water storage capacity,and shallow groundwater reevaporation coefficient.The runoff in the region had a large uncertainty value,and the uncertainty of downstream hydrological stations was greater than that of upstream stations.The coefficients of determination(R~2)and Nash–Sutcliffe efficiency coefficients for the evaluation markers for monthly runoff rate and validation results at various stations were all above 0.6,and simulation accuracy satisfied the requirements.4.Joint simulation of surface and groundwater.We developed infiltration/evaporation and water level couplers to achieve correspondence between the spatial distribution of the coupled models and calculated output parameters.The coupled models were applied for the joint simulation of shallow pore and surface water in the Changzhi basin.Protocol comparison found that the simulation result of the SWAT–Visual MODFLOW coupled model was better than those of Visual MODFLOW alone.5.Prediction of water resources.Precipitation caused by the convergence process of different components of the change trend is different.We found that as the amount of precipitation increased,other components during runoff increased accordingly,except for soil water storage capacity,which showed small changes.The magnitude of increase in the amount of groundwater recharge,surface runoff,and actual evapotranspiration were 84%,80%,and 11%,respectively.The percentage variation trends of various components in the total runoff of the river channel during convergence differed.The percentage of base flow significantly increased(+34%),and the percentage of lateral runoff significantly decreased(-50%),whereas changes in the percentage of surface runoff were not significant.Under current mining conditions and a reduction in mining by 10%and 20%,the total amount of shallow pore water in the Changzhi basin was in a state of negative equilibrium.However,as groundwater mining decreased,the negative equilibrium significantly decreased accordingly.The water table is gradually rising.The innovation of this paper was to develop SWAT-MODFLOW coupler.The combined simulation of shallow pore water and surface water in Changzhi basin is realized.The transformation mechanism of surface water and groundwater in turbid Zhuozhanghe drainage basin was further clarified.The driving factors of water conflicts in the turbid Zhuozhanghedrainage basin are clarified in terms of the accuracy of the three tributaries of haihe drainage basin.