Rainfall Infiltration in Chinese Loess by In Situ Observation

Abstract

This study was conducted to investigate the recharge of surface water to groundwater in the Chinese loess area. A monitoring site was set up in Zhengning County, Gansu Province, China. The results show that the shallow layer (within 2 m) is greatly affected by rainfall, evaporation, and the moisture content changes in the annual cycle; the trend is consistent with the change of evaporation. When the precipitation exceeds a certain threshold, the moisture content changes at a deep position. The increment of the soil moisture content rises with the increasing precipitation, decreases with the depth, and lags with time. The results appear to confirm that water conducts in the unsaturated soil below the soaked zone through unsaturated migration. The motion of the water vapor is very small but can not be ignored. The water would accumulate when encountering the paleosol bed of low permeability; as a result, loess landslides might eventually be induced.