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

Abstract. Large gullies in dryland landscapes are often viewed as indicators of land degradation, yet in some settings they may serve critical ecohydrological functions—supporting groundwater recharge and subsurface connectivity. In China’s Loess Plateau, we assess these functions in the Nianzhuang Catchment using a multi-indicator 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 gully zones, while deeper fissure water is replenished more slowly through percolation from the upper layers. Restoration interventions—particularly check dams and ponds—act as focal points for groundwater infiltration, enhancing recharge in otherwise limited dryland systems. Estimated annual recharge (238–241 mm) accounts for over 43 % of annual precipitation, far exceeding typical rates observed in nearby tableland and hilly areas. These findings revise prevailing assumptions by positioning gullies not simply as degraded features, but as hydrologically active zones that can buffer seasonal variability and support ecosystem resilience. The study advances a conceptual framework for using isotopic damping, chloride accumulation, and recharge partitioning as indicators of landscape function in semi-arid regions, offering valuable tools for dryland monitoring and restoration planning.