Numerical Simulation Of Karst Groundwater And Analysis Of Groundwater Reservoir Capacity In Pingzhai Reservoir Area,Guizhou

Rainfall in central Guizhou is abundant,but its temporal and spatial distribution is extremely uneven.The karst aquifer is heterogeneous.These natural factors lead to poor storage capacity of the karst groundwater system,which has adverse effects on irrigation and urban water supply.Groundwater reservoirs have strong storage space and storage capacity,which can store groundwater and optimize the configuration of groundwater,so they have attracted much attention.This paper establishes the groundwater seepage model before and after the impoundment of Pingzhai Reservoir,and then discusses the storage capacity distribution and regulation and storage capacity of groundwater reservoirs,and provides a basis for the effective planning and management of groundwater resources in the future.This paper has collected and sorted out 53 drill holes in the Pingzhai Reservoir area(hereinafter referred to as the study area)that have relatively complete exposures and good control over their distribution points.In some areas where borehole data is lacking,50 virtual boreholes were reasonably added,for a total of 103 boreholes.Then,using the geological modeling tools in the GMS software,a three-dimensional geological structure model containing the Triassic strata and the Permian upper strata was established.On the basis of the geological model,according to the field survey data and hydrogeological data,using the conceptual modeling method of GMS and the CFP program,the boundary conditions,hydrogeological parameters,source and sink items of the model were determined respectively.Among them,the assignment of hydrogeological parameters and pipeline-related parameters(diameter,tortuosity,roughness,etc.)should fully consider the geomorphic topography,stratum lithology,karst development degree and previous hydrogeological parameter empirical values.The initial value is given first,and then the final parameters are obtained by inversion of the parameters based on the monitoring hole water level data and the karst pipeline outlet flow monitoring data.Finally,before the impoundment of the Pingzhai Reservoir and when the reservoir reaches the normal water level,the karst pipeline-porous medium groundwater coupling seepage model in the reservoir area was established,and the groundwater seepage field changes,pipe parameters sensitivity and groundwater balance in the study area were analyzed.Based on the groundwater seepage model,Arc GIS software is used to analyze the spatial overlap of karst aquifer phreatic level elevation and floor elevation,and study the spatial distribution law of the characteristic storage capacity of the underground reservoir.Then,the characteristic storage capacity was counted by district,and the characteristic storage capacity of different regions was calculated.The specific conclusions are as follows:(1)The distribution of total storage capacity and dead storage capacity are similar.The Triassic strata in the southeast of the study area are thick,and the storage capacity per unit area is the highest.(2)The storage capacity in the area from Pingzhai Dam to Shuguang Town is relatively large,which is an important area for the storage capacity of underground reservoirs.(3)The total storage capacity of the study area is approximately 2.6121 billion m~3,the dead storage capacity is approximately2.1859 trillion m~3,and the regulated storage capacity is approximately 426.2 million m~3.(4)Divide the study into 12 areas,and combine several areas with more developed karsts into one sub-area of the study area.According to calculations,the total storage capacity of the sub-area of the study area is about 1.8921 billion m~3,the dead storage capacity is about 1.5605 billion m~3,and the regulated storage capacity is about 331.6 million m~3.Among them,the volume of carbonate rock in NO.11 area of the study area only accounts for 32.02%of the total volume of carbonate rock,while the proportions of total storage capacity,dead storage capacity,and regulated storage capacity reach 43.74%,38.72%,and 69.50%,respectively.It can be seen that this area is the key area for the regulation and storage capacity of the reservoir area.