Separating recharge receptivity from flood-water availability for managed aquifer recharge in Wadi Qanunah, Saudi Arabia: a physically informed framework corroborated by an operational well network

Abstract

Managed aquifer recharge (MAR) can convert episodic floodwater into strategic groundwater storage in arid wadis, but conventional suitability mapping often conflates subsurface recharge receptivity with access to deliverable water. We developed a physically informed, non-compensatory framework for Wadi Qanunah, southwestern Saudi Arabia. Recharge receptivity was derived from AHP-weighted lithology, slope, sand fraction, and distance to drainage, with bounded penalties for electrical conductivity and root depth. Flood-water availability was estimated independently from rainfall-weighted D8 flow accumulation and distance-decayed accessibility to qualifying channels using GPM IMERG V07 and CHIRPS v3 RNL rainfall (2003–2024). The components were integrated by geometric mean, an availability veto, and landsurface constraints. Flood-water availability is therefore a relative routed-water accessibility metric rather than simulated runoff discharge or event-specific flood yield. Replacing IMERG with CHIRPS changed basin-scale routed volume by about 22% but produced nearly identical MAR rankings (Spearman ρ =0.9986). Seven hydraulically distinct candidate sites remained persistent across 119 structural and AHPweight perturbation scenarios, with diversion distance as the dominant structural uncertainty. Post-selection spatial corroboration using 56 operational production wells showed strong concentration within highpriority MAR zones; these wells provide operational hydrogeological context rather than independent field validation. The framework provides a robust screening basis for prioritising MAR field investigations by explicitly separating recharge receptivity, routed flood-water accessibility, and operational groundwater context, while site-scale infiltration and hydraulic testing remain necessary before implementation.