It is also clear that among homogeneous vadose zone, precipitation recharge coefficient of sand soil is larger than that of clay soil, and moreover, the precipitation recharge coefficient of sabulous clay involved lamella clay is minimum. 当包气带岩性单一时,降雨入渗系数随岩性的不同而变化,即砂质土大、粘性土较小,而含有薄层粘土夹层的亚砂土最小。