Study On Surface Water Quality Protection And Restoration Methods In Coal Mining Areas With High Groundwater Level

After the underground coal resources are exploited in the mining area with high groundwater level,the surface often sinks to form a collapsed water area,which makes some areas gradually change from terrestrial ecosystem to a comprehensive ecosystem with land-water interaction.The ecological reconstruction of land reclamation in mining areas at home and abroad has gradually changed from the initial single engineering measures to the comprehensive utilization of regional resources and the integrated construction of landscape,aiming at forming a stable,healthy and sustainable mining area ecosystem.In the process of ecological restoration in mining areas with high groundwater level,how to develop and make good use of the water bodies in subsidence areas,and deal with the problems of water system closure and water pollution to restore the land and water ecosystem should be the focus of attention in mining areas with high groundwater level.Therefore,this thesis collected the topographic and water quality data of Yanzhou mining area through field experiments,and based on in-depth analysis of the hydrological situation of Yanzhou mining area,aiming at the problems of disordered surface runoff and poor water quality,it put forward the measures of connecting corridors with water system and riparian vegetation buffer zone to protect and repair the surface water quality,so as to achieve the governance goal of connecting water system,cleaning water quality and enhancing the vitality of mining area ecosystem.The main research results are as follows:(1)The general situation of surface hydrology in Yanzhou mining area was analyzed,and the water quality problems and their influencing factors in the study area were revealed.The cultivated land and water area in Yanzhou mining area account for more than 50%,and there is a large amount of subsidence water.Through sampling and analysis,the water quality data of Yanzhou mining area was obtained,and the water quality inversion model was established in combination with remote sensing data.It was analyzed that the concentrations of TP,TN and TSS showed a good trend from 2014 to 2021,but some water bodies still reached the requirements of Class V water quality or even exceeded the requirements of Class V water quality.Further analysis of land use structure around water body and its relationship with water quality shows that cultivated land and water body account for the largest proportion,and water quality parameters have significant correlation with the proportion of cultivated land area,which is greatly affected by cultivated land non-point source pollution.Based on the runoff simulation,the material flow process in the study area is analyzed,and the direction of surface water quality protection and restoration is put forward according to the specific problems.(2)The method of protecting and restoring surface water quality based on water system connecting corridor is put forward.The morphological spatial pattern analysis(MSPA)method was used to analyze the source data,and 45 core areas characterized by LCP,IIC and PC index were selected as ecological sources.Combined with the planning purpose,land use type,soil type,slope,elevation and water surface elevation are selected as resistance factors,and the weight of each resistance factor is determined by principal component analysis to construct the resistance surface.Constructing water system connecting corridor based on minimum cumulative resistance model;Optimize the planned water network in combination with natural rivers,potential runoff paths and corridor widths,and obtain the construction scheme of water network connectivity;Finally,based on geostatistical function and hydraulic gradient,the effect before and after water system connection is evaluated.The results show that the hydrological connectivity and hydraulic gradient of the study area are significantly improved after the construction of water system network,and the maximum distance of water system connection is extended,thus realizing the improvement of water power in the study area.(3)Put forward the method of constructing riparian vegetation buffer zone on the basis of water system connecting corridor to protect and repair surface water quality.The site conditions of the study area are determined by slope,Manning coefficient,soil water storage capacity and soil saturated hydraulic conductivity in Yanzhou mining area,and the spatial distribution of riparian vegetation buffer zone in the study area is simulated and drawn based on Phillips time model.The simulated riparian vegetation buffer zone area(in the study area)is 5.59km2,of which 2.18km2 is covered by vegetation,so it is necessary to add 3.41km2 riparian vegetation buffer zone.Finally,the SWAT model is used for scenario analysis,and the results show that the reduction rates of TN and TP in the study area by riparian vegetation buffer zone are above 10.14% and 14.94%,and the vegetation buffer zone can achieve the goal of improving the water quality of the study area and realizing the sustainable development of the ecosystem.