Study On Dynamics Of Fractured Karst Groundwater Level In Xiaozhuang Water Source Area

Jiyuan City is an emerging city located in the northwestern part of Henan Province,the birthplace of Guji Water.The northwest is adjacent to Jincheng,Yuanqu and Yangcheng counties in Shanxi Province,east to Qinyang City and Mengxian County,south to Xin'an County and Mengjin City across the Yellow River,and Houyue Railway and Jiaozhi Railway meet here.The Changji-Erguang Expressway is bordered by the east of the city and the traffic is very convenient.Jiyuan City is a new city with developed industries,rapid economic development and large water demand.The Xiaozhuang water source is located at the exit of Kejing Basin in Jiyuan City.It is currently the only water supply source in Jiyuan City.The mining volume has increased from the initial 20,000 m~3/d to 80,000 m~3/d,which is mainly used for urban residents'domestic water.On the basis of fully understanding the regional geological structure and hydrogeological conditions,combined with the multi-year dynamics of the fractured karst groundwater level in the Xiaozhuang water source,the groundwater level is mainly affected by factors such as precipitation,mining volume and water storage in the Manghekou Reservoir.It can be seen from the water level dynamic curve that the water level is relatively high during the high-precision precipitation period;when the mining volume increases sharply,the water level also continues to decrease.In 2014,the Manghekou Reservoir began to store water,and the water source in the water source rapidly recovered.In 2015,the reservoir did not store water,and the water source level decreased.In 2016-2018,the reservoir was stored for three consecutive years,and the groundwater level rapidly recovered.Using stepwise regression calculation method,the main factors affecting the change of water level are the water level in the first January,the exploitation amount in the current month,the precipitation in the first two months and the reservoir capacity of the Manghekou Reservoir.The water level in the first January reflects the comprehensive influence of the factors such as the first January and the previous months on the water level in the same month,and the regression coefficient of the precipitation in the first two months in terms of precipitation.The absolute value is the largest,which can prove that the peak water level lags behind the peak precipitation for2 months.Based on the results of stepwise regression calculation,the monthly groundwater level in different time periods is analyzed and predicted by using time series,BP neural network and grey theory.The average relative error of the model calculation results is below 5%,and the prediction effect is better.In the case of comparison of long-sequence prediction results,the time series model has higher prediction accuracy;in the case of comparison of short-sequence prediction results,the gray model has higher prediction accuracy.Based on four different prediction models,the groundwater level of the water source is predicted and analyzed.From the perspective of sustainable utilization of groundwater resources,the allowable exploitation of fractured karst groundwater in Xiaozhuang water source is determined to be 80,000 m~3/d.