Groundwater threshold of ecological vegetation in Qaidam Basin

The groundwater threshold of ecological vegetation is defined as the maximum depth to the water table and the maximum total dissolved solids (TDS) of groundwater on which the growth of vegetation depends. The basis for controlling the ecological risk of groundwater exploitation is to clarify the dependency of ecological vegetation and groundwater and determine the groundwater threshold. Based on the measured data obtained by remote sensing dataset MOD13Q1 and hydrogeological survey, the relationship among ecological vegetation, burial depth and TDS of the phreatic water in the main plain area of the Qaidam Basin is statistically analyzed. The results show that ① the threshold of natural vegetation-dependent groundwater is 5.3 m for depth of water table and 7.5 g/L for TDS, and natural vegetation growing in areas where the water table depth is more than 5.3 m is basically independent of groundwater. ② Water table depth ＜1.1 m is suitable for aquatic, hygrophilous vegetation and hygrophilous saline-resistant vegetation. Water table depth ranging from 1.4 m to 3.5 m is suitable for saline-resistant vegetation, middle vegetation and xerophytic vegetation. ③ TDS of ≤1.5 g/L is suitable for vegetation growth, 1.5 g/L7.5 g/L is not suitable for vegetation growth.