Analysis of the contribution of rainfall to recharge in the Mu Us Desert (China) based on lysimeter data

Scarce rainfall and strong evaporation add complexities to estimating groundwater recharge in arid and semiarid regions. There are still many gaps in the understanding of how soil water near the ground surface interacts with the atmosphere, which increases the difficulties of determining the contribution of rainfall to groundwater in these regions. This study used a weighing lysimeter to observe the potential recharge over a 1-year period in the Mu Us Desert, northwest China. The observed data were used to explore the infiltration processes and to quantify recharge. The results show: (1) no potential recharge can be observed if the rainfall is less than 12.3 mm/day during the experimental period. The observed annual potential recharge was 29.3 mm, which accounted for 10% of the annual rainfall. (2) The threshold of soil-water content for potential recharge was determined, such that when the average soil moisture along the soil profile (0–100 cm) is larger than 0.12 cm³/cm³, the potential recharge can be observed. (3) The empirical weight function (Poisson distribution) method performed well in the estimation of recharge compared to the observed lysimeter data. In addition, the parameter γ of the Poisson distribution has a linear relationship with the average soil-water content along the soil profile. These findings can help researchers understand recharge, which has significance in groundwater resource management.