Characteristics of Recharge in Response to Rainfall in the Mu Us Sandy Land, China

Water scarcity is a significant issue in arid and semi-arid regions and improving our understanding of infiltration and recharge processes is crucial for water resource management. In this study, weighing lysimeters were employed in Mu Us Sandy Land, China to continuously monitor soil water content and recharge rates during the non-freezing seasons from April 2021 to October 2023. The performance of three empirical weight functions, including Poisson, Rayleigh, and Gamma distributions in simulating the recharge process was evaluated. The results indicate that: (1) The process of groundwater recharge displays significant interannual and seasonal differences. Due to low initial soil moisture and scarce rainfall, recharge accounts for only 10.9% of the averaged annual rainfall in 2021. Due to extreme rainfall events (126.8 mm), groundwater recharge increased by 649.4% compared to 2021, accounting for 51.2% of the annual rainfall in 2022. Because of relatively high soil moisture, groundwater recharge accounted for 18.3% of the annual rainfall in 2023. (2) The Poisson empirical weight function is more suitable for simulating a gradual increase in recharge rate, while it fails to accurately capture the rapid rise in recharge rates associated with extreme rainfall events. (3) Compared to the Poisson empirical weight function, the Gamma distribution performs better under extreme rainfall conditions. This study provides a detailed analysis of groundwater recharge dynamics in semi-arid regions and offers technical support for a deeper understanding of groundwater recharge processes.