The impact of vegetation coverage increase on groundwater recharge in the arid regions of Northwest China: Experimental and numerical study

With the implementation of ecological restoration projects in Northwest China, the eco-environment has been improved continually, accompanied by the increase of vegetation coverage. The water consumption by plants will make the soil water deficient severely and reduce the groundwater recharge. In this study, the soil matric potential at the depth was measured in the vegetated and bare soil lysimeters in situ. The results show that the thaw and frozen period in the two lysimeters is similar and has less effect on groundwater recharge. The soil matric potential in the vegetated lysimeter (-74kPa) is much lower than that (-16kPa) in the bare soil lysimeter with the coexistence of evaporation and transpiration. Soil water moves upward mainly in the vegetated lysimeter. In contrast, soil matric potential is high and soil water moves downward below 40cm, and thus groundwater can be recharged continually. Long-term simulation was carried out using Hydrus-1d to identify the quantitative relation between vegetation coverage increase and groundwater recharge. The results indicate that groundwater recharge varied from 82mm/a to 333mm/a with the average of 197mm/a and the average infiltration coefficient was 0.53 in bare soil area. While in vegetated area, groundwater recharge was almost zero. Finally, the impact of vegetation coverage increase on groundwater recharge is discussed with respect to plant transpiration and canopy interception, and suggestions on the harmonic development of water and ecology in arid zones are put forward.