Research On The Development And Protection Of Karst Backup Water Sources In The Western Baoshan Basin

With the accelerating process of urbanization,the rapid expansion of cities and the rapid increase of population,the problems of urban water resource shortage and water pollution aggravation have become increasingly prominent.The supply of high-quality water resources has become one of the restricting factors affecting the scale and direction of urban development.Therefore,it is very urgent to strengthen the construction and management of urban reserve water source area.In this paper,the development and protection of karst reserve water source in the west of Baoshan Basin is taken as the goal.Firstly,through the investigation and analysis of the topography and landform,stratigraphic lithology and hydrogeological conditions in the west of Baoshan Basin,and combining with the borehole data,the three-dimensional geological model of the study area is established.Then,the amount of natural recharge and recoverable groundwater resources in the study area are calculated by using rainfall infiltration coefficient method and mining coefficient method,and the water quality analysis and environmental quality evaluation are carried out.The environmental impact of groundwater exploitation is analyzed from four aspects:karst collapse,land subsidence,spring drying up and groundwater pollution.In the analysis of land subsidence,the overlying Quaternary loose layer's overflowing recharge to the underlying carbonate aquifer is considered.The flow field models under the two conditions are established,and the shape characteristics of the flow field under the conditions of dividing two groundwater systems in the hydrogeological unit and not further dividing the groundwater systems are compared and analyzed.According to the hydrogeological conditions and the current situation of water resources utilization in the study area,the constrained conditions of water quantity,karst collapse,land subsidence,spring drying up and groundwater pollution in the water source area were shown through pictures.The optimal mining scheme was proposed by using the response matrix method combined with the groundwater flow field model.Finally,the pollution prediction of characteristic pollutants in the study area is made and the scope of water source protection area is delimited according to relevant regulations.The results show that the average natural recharge amount of groundwater in the hydrogeological unit of western Baoshan Basin is 25,321,100 m~3/a(69,400 m~3/d),the allowable exploitation amount of groundwater is 20,706,700 m~3/a(56,700 m~3/d),and the average optimized exploitation amount of groundwater is 8,267,900 m~3/a(22,700 m~3/d)for many years.The water source area also has great water supply potential.According to the status quo mining,no environmental geological problems will occur,but reasonable mining should be paid attention to.The shape characteristics of the flow field are basically the same when the two groundwater systems are divided into two hydrogeological units and when the groundwater systems are not further divided.At the same time,the pollution prediction results show that about 55 years later,the groundwater in the water source area will be affected.