海河平原典型傍河含水层降雨入渗补给阈值效应及空间特征OA

The Haihe Plain was identified as a resource-based water shortage area,where excessive groundwater exploitation led to a number of ecological and environmental issues.Groundwater levels around the replenishment channels recovered due to ecological water replenishment techniques,such as diverting water from the South-to-North Water Transfers Project and releasing water from upstream reservoirs,in key sections of the Beijing-Hangzhou Grand Canal.In the riverside aquifer within the ecological water replenishment zone,canal leakage was found to cause variations in groundwater level and depth with distance from the river,resulting in significant spatial and temporal differences in rainfall infiltration recharge patterns. The groundwater response to individual rainfall events was analyzed using methods such as the water table fluctuation method,correlation analysis,segmented regression,and stepwise regression,based on detailed monitoring of groundwater levels in a typical riverside aquifer section along the South Canal in Cangzhou,Haihe Plain.The spatiotemporal characteristics of rainfall infiltration recharge in small-scale riverside areas were investigated,and the underlying causes were identified.An estimation equation for quantifying infiltration recharge from individual rainfall events was established. The results indicated that groundwater dynamics in the riverside area exhibited distinct seasonal variations:water levels were generally elevated during the rainy season due to rainfall infiltration and recharge and remained relatively stable during the dry season.Spatially,groundwater levels were observed to gradually decrease with increasing distance from the riverbank,and seasonal differences were found to diminish.A clear threshold effect was identified in the groundwater response to rainfall:when rainfall was small,water levels increased slightly with rainfall amount,but when rainfall exceeded a response threshold(from 25 to 65 mm),water levels increased significantly.The response time of groundwater to rainfall was shortened as the rainfall amount increased,and the response threshold was determined to be 60 to 80 mm.When rainfall fell below this threshold,response time decreased with increasing rainfall;when rainfall exceeded the threshold,response time stabilized at around 1.5 hours.Spatially,as groundwater depth increased,the response threshold was gradually raised,and the total rainfall infiltration recharge was progressively reduced.Furthermore,increased rainfall intensity was found to significantly reduce the efficiency of rainfall infiltration and recharge. It was further observed that in the riverside aquifer,the river influenced rainfall infiltration patterns by altering groundwater depth,causing infiltration recharge to gradually decrease with increasing distance from the riverbank.The factors influencing infiltration recharge from individual rainfall events were identified,and an estimation equation was developed.The simulation results revealed that infiltration recharge was positively correlated with rainfall amount and negatively correlated with rainfall intensity,groundwater depth,and distance from the river.The coefficient of determination(R2)for the simulation was calculated as 0.76.This research was considered to provide scientific support for the development,utilization,and protection of groundwater resources in riverside areas.