The Study On Optimization Of Groundwater Monitoring Network In Typical Land Subsidence Area

As a valuable resource for human survival and development,groundwater resources have always played an important supporting role in social and economic development.However,in recent years,the unreasonable exploitation and use of groundwater resources to support rapid and steady economic development has led to the formation of groundwater landing funnels in some areas,which are distributed in different aquifers and have different degrees of impact.The fall of groundwater levels has also led to geoenvironmental disaster problems such as ground subsidence,karst collapse and seawater intrusion.Rational optimisation of the existing groundwater monitoring network in geological disaster areas,improving the functions of the monitoring network,increasing the monitoring accuracy,and timely and accurate monitoring of dynamic changes in water levels in disaster development areas are effective ways to establish a water resources monitoring system,build a modern water network,and provide information support for geological disaster prevention and control and prevention.This paper conducts an overall optimisation study of the groundwater level monitoring network in the ground subsidence area of the Northwest Lu Plain.The degree of exploitation of groundwater resources in the study area is high,and the existing groundwater level monitoring network in the region has an unreasonable distribution of monitoring points due to the early construction time,and the monitoring data lacks representativeness,so the actual monitoring capacity cannot adapt to the new monitoring function.Therefore,in this study,a combination of cluster analysis,hydrogeological analysis,ordinary Kriging method and time series analysis was used to optimise the groundwater monitoring network in the study area,and the main results achieved were:(1)The influencing factors of groundwater level dynamics and elements related to ground subsidence development in the study area were identified.According to the regional hydrogeological conditions,the single influencing factor of the shallow and deep groundwater level and the elements related to ground subsidence were zoned,and the zoning map of the dynamic influencing factor of the shallow groundwater level and the zoning map of the dynamic influencing factor of the deep groundwater level combined with the ground subsidence factor were obtained by using the zoning space overlay.(2)The monitoring density of the shallow and deep groundwater level monitoring network in the ground subsidence development area was optimized.The shallow and deep redundant monitoring wells were removed from 23 and 7 wells respectively,and 43 shallow groundwater monitoring wells and 72 deep groundwater monitoring wells were added to improve the monitoring accuracy of the regional groundwater monitoring network,achieve coverage of the ground subsidence development area,and make the monitoring points more reasonable,so that according to the hydrogeological conditions,ground subsidence influencing factors and subsidence development rate of the sub-area in which the monitoring wells are located,combined with The network can respond effectively to the development trend of regional ground subsidence hazards based on the hydrogeological conditions of the sub-areas in which the monitoring wells are located,the factors affecting ground subsidence and the rate of subsidence development,combined with the water level monitoring information at the monitoring points.(3)The spatial distribution of the groundwater monitoring network was evaluated for reasonableness.The standard deviation of the estimated errors of the monitoring network before and after the optimization was calculated using the ordinary Kriging method,and the spatial layout of the shallow and deep groundwater monitoring networks was appropriately adjusted according to their estimated error distribution.The standard deviation of the estimated error of the shallow groundwater monitoring network was reduced from 0.71 to0.40,and that of the deep groundwater monitoring network was reduced from 1.74 to 0.56.The monitoring accuracy was greatly improved,and comprehensive monitoring of groundwater levels in the ground subsidence area was achieved.(4)The frequency of deep groundwater level monitoring in the ground subsidence development zone was optimized.Based on the groundwater level monitoring data in the ground settlement development area,the monitoring frequency that can accurately monitor the dynamic changes of the deep groundwater level in the settlement development area is determined to be 6 times/month using the time series analysis method under the conditions of meeting the water level trend test and periodic change identification in the ground settlement development area...