Application of Unsaturated Zone Environmental Tracers to the Estimation of Rainfall Infiltrating Rate in the Zhangye Basin, Northwestern China
利用包气带环境示踪剂评估张掖盆地降水入渗速率

The rainfall infiltrating rate is a key parameter in groundwater resource assessment and groundwater protection. During the groundwater resource assessment in middle basins of the Hexi corridor in the past decades, however, the rainfall infiltration was not considered where the buried depth of the water table was more than 5 m. In the present work, the rainfall infiltration rates were estimated using chemical and isotopic information in the unsaturated zone at two sites of the Zhangye basin, which lies in the middle reaches of the Heihe River. One site is located in sand dunes in the middle of the basin and the other site is located in a wasteland area with the buried depth of the groundwater table being 8.6m. The result of chloride mass balance (CMB) indicates that there exists rainfall infiltration in Zhangye basin where the buried depth of the water table is more than 5 m. In the sand dune area, the rainfall infiltrating rate is 13.3~14.4 mm/a with the buried depth of the water table being 6.3 m, and the infiltration coefficient is about 0.10~0.11%. In the wasteland area, the rainfall infiltrating rate is 16.8~18.4 mm/a with the buried depth of the water table being 8.6m, and the infiltration coefficient is about 0.13~0.14.