Study On The Establishment Of Protected Area Of Concealed Karst Water In Daxing Overlapping Area

Because of its good water quality and abundant water resources,the concealed karst water source of Daxing overlapping area is an important water source for industrial agriculture and human life in Beijing.The karst aquifer is closely related to the overlying Quaternary aquifer,once the karst aquifer is polluted by human activities,it will be difficult to control and repair.From a long-term point of view,in order to ensure the safety of water supply,it is necessary to protect the quality of bedrock water.The most effective way is to divide the protection area of karst water source,so as to provide a scientific and effective basis for the mining and protection of the hidden karst fissure water source in this area.The results are as follows:Based on the analysis of the hydrogeological conditions,pollution and various factors that may affect the quality of karst water in the study area,this paper establishes the refined groundwater model and the special vulnerability evaluation model of karst water in the study area,and evaluates the special vulnerability of the hidden karst water in the study area by using the superposition index method,so as to carry out the study of method of establishing protection area of hidden karst water source in the study area The results are as follows:1.The unstructured grid numerical model of groundwater flow in the study area is established.2.The evaluation model of the special vulnerability of the concealed karst water in Daxing overlapping area is constructed.The evaluation index system of K(horizontal permeability coefficient of karst aquifer)L(landuse type)I(surface infiltration supplement)V(vertical permeability coefficient of Quaternary confined aquifer)H(head difference of Quaternary confined aquifer and karst aquifer)is established,and the weight of each index is determined by fuzzy analytic hierarchy process.3.The special vulnerability of karst aquifer in the study area is evaluated.The results show that the areas of high vulnerability area,high vulnerability area,medium vulnerability area,low vulnerability area and low vulnerability area in the study area are 11.32km~2,91.9km~2,293.23km~2,138.75km~2 and 20.5km~2 respectively,accounting for 2.04%,16.54%,52.77%,24.97%and 3.69%of the total area of Karst aquifer distribution.The overall vulnerability trend is high in southwest and low in Northeast,The vulnerability of karst aquifer of Daxing is generally higher than that of Tongzhou area.4.Method of establishing protection area was founded.The first-level protection area and quasi-protection area are established in the Niantan water source of Daxing area,which are 22.87km~2 and 30.67km~2 respectivly;and quasi-protection zone of21.73km~2 is established near the Donggaodi water source.Put forward different anti pollution protection measures for different levels of protection areas.It is strictly prohibited to build,modify and expand projects without water supply equipment and water source protection in the first level protection zone of karst water source area;it is strictly prohibited to build,modify and expand projects with serious pollution risk to water quality in the quasi protection zone of karst water source area.In the reconstruction of a construction project,no increase in the discharge of pollutants shall be allowed.