Reframing gullies as recharge zones in dryland landscapes of the Loess Plateau, China

Abstract

Large gullies in dryland landscapes are often indicators of land degradation by surface runoff. However, under conditions where gully systems are hydrologically arrested by restoration interventions that increase water residence time – most notably check dams and ponds – they may also function as hydrologically active zones of groundwater recharge and subsurface connectivity. In China’s Loess Plateau, we assess these functions in the Nianzhuang Catchment using a multi-indicator, process-based approach that integrates stable isotopes (δ2H, δ18O), chloride concentrations, and groundwater level fluctuations. Our results show that precipitation is the dominant source of recharge for shallow pore water within engineered gully zones, while deeper fissure water is replenished more slowly through percolation. Hydrological arrest through ecological engineering interventions acts as focal points for groundwater infiltration, enhancing recharge in otherwise limited dryland systems. Estimated annual recharge in the monitored gully-zone pore aquifer (238–241 mm) is equivalent to about 43 % of the mean annual precipitation at the site, a site-specific recharge magnitude that far exceeds reported catchment-wide recharge rates observed in nearby tableland and hilly areas. Our results indicate that engineered gully systems can act as focused recharge zones rather than solely degraded landforms. By linking runoff convergence and ponding to measurable recharge responses, the study provides a process-based framework for assessing groundwater dynamics in managed semi-arid landscapes.