北方岩溶区降水入渗补给系数及补给机制:以羊庄岩溶水系统为例OA北大核心CSTPCD

[Objective]To establish a series of hydrogeological parameter for karst areas in North China,an on-site experimental study on water balance has been carried out since the 1980s in a closed spring-drainage karst wa-ter system in Yangzhuang,Shandong Province.[Methods]Based on long-term field observations of water balance elements spanning more than 40 years,the formulas for calculating precipitation infiltration recharge coefficients in bare,semi-covered and covered karst areas were derived.The correlation equations of the precipitation infiltration recharge coefficient α with precipitation P and water table depth D,as well as the series of adjustable maximum precipitation infiltration recharge coefficients in karst areas,were also established.The processes of precipitation infiltration and recharge and the mechanism of α change were explored.[Results]The results showed that α varied with D.Each rainfall segment P corresponded to a maximum precipitation infiltration recharge coefficient αmax and a maximum precipitation infiltration recharge volume,namely,the recharge limit Gmax,while the corresponding depth of water table was the optimal depth of water table Dcritical.When D was greater than Dcritical,the interception of the vadose zone increased with increasing water table depth and α was less than αmax.When D was less than Dcritical,the surface runoff increased with decreasing water table depth and α was less than αmax.Different rainfall segments cor-responded to different Dcritical,and the corresponding αmax and Dcritical increased with increasing precipitation.At any water table depth,Gmax was constant and equal to the difference between the critical rainfall of saturation excess runoff and the maximum interception volume of vadose zone.[Conclusion]This study addressed the key scientific issues related to precipitation infiltration recharge in karst areas and improved the research level of karst water re-sources in North China.