Land-cover change threatens oases' sustainability: Vadose-zone recharge and spring dynamics in the Jerusalem mountains

This study focuses on the Jerusalem Mountains, a karstic ridge in the Mediterranean-semi-arid transition zone of Israel. The region hosts perched springs that sustain small but ecologically and culturally important oases, embedded within a landscape of rugged topography, fault-controlled subsurface structure, and variably thick vadose zones. We present a multi-decadal, mechanistic assessment of perched-spring hydrology, integrating seven decades of land-cover reconstruction from pre-satellite aerial imagery with a transient, high-resolution 3D flow model. The model explicitly represents fault-bounded perched compartments, variably thick vadose zones, and both matrix and preferential-flow domains. A spatial proxy based on historical moist-soil (“oasis”) extent provides independent qualitative validation of long-term trends. This combined reconstruction-modeling framework enables quantitative evaluation of how afforestation and urbanization alter recharge pathways, perched-saturation dynamics, and spring discharge in a structurally complex karst ridge. Results show that afforestation and urbanization consistently reduce perched-spring discharge by decreasing net infiltration and lateral connectivity between perched horizons. The spatial distribution of spring loss reflects structural controls: most dried springs occur in small, fault-bounded catchments with thin vadose profiles, whereas larger central catchments with thicker vadose zones remain more resilient. These findings demonstrate that land-cover change can exceed the intrinsic buffering capacity of perched aquifers. The framework provides a generalizable approach for diagnosing vulnerability and supporting subsurface-informed land-use planning, contributing to the sustainable management of groundwater-dependent ecosystems and oases in Mediterranean-semi-arid karst landscapes. • Multi-decadal model links land-cover history with perched-spring dynamics. • Afforestation and urbanization reduce recharge and weaken perched springs. • Structural heterogeneity controls spring sensitivity to land-cover change. • Extreme wet years create long-lived recharge pulses in thick vadose zones. • Oasis-extent proxy validates modeled long-term spring-discharge trends.