Calculating precipitation recharge to groundwater applying envieronmental chloride tracer method

Precipitation infiltration recharge of groundwater has happened great change in North China Plain, caused by thick unsaturated zone going with groundwater level´s drop, because of long-term sustainable mining. In this paper, rainfall infiltration recharge, in typical section of Piedmont Plain, was calculated applying environmental chloride tracer method, followed by objectivity analysis to the results. Rainfall infiltration coefficient, calculated by Chloride Accumulated Method, are 2.17%(K1) and 4.38%(K2), while infiltration quantity are 11.54mm/a(K1) and 23.29mm/a(K2) in current groundwater level (30m). Compared to the average value of this zone in 1985, 0.28, and the highest value, 0.37, and the lowest value, 0.18, the coefficient reduced significantly.