Dominating effect of extreme precipitation over potential groundwater recharge beneath shallow rooted vegetation

Abstract

Potential groundwater recharge (PGR) beneath shallow-rooted vegetation, a dominant ecosystem in temperate and arid regions, remains poorly understood. Current global syntheses are hindered by methodological inconsistencies and mixed temporal scales, particularly in relatively homogeneous soil environments like the Loess Plateau, where shallow-rooted crops/grasslands dominate but regional PGR controls are uncharacterized. This study uses the tritium peak method (35 profiles, tritium peak depth 3.6–26.4 m) and partial least squares structural equation modeling (PLS-SEM) to quantify PGR (8.8–93.0 mm yr⁻¹ over the past five decades, mean 43.0 ± 3.7 mm yr⁻¹) and drivers. Extreme precipitation (EP) is the sole significant driver, explaining 50.5 % of PGR variance (path coefficient = 0.667, p < 0.001), with negligible empirical effects of soil texture (silt-dominated), shallow roots (95 % above 2.0 m), and soil hydraulic properties. The tritium method’s unified temporal scale (past five decades) and single-variable design eliminate parameter biases, confirming EP-driven pulse infiltration bypasses shallow roots and relatively homogeneous loess soils. This study reveals PGR in shallow-rooted, uniform soil systems is climate-dominated, offering an EP-centric framework for regional hydrological modeling and water management globally.