A Spatial Framework for Assessing Irrigation Water Use in Overexploited Mediterranean Aquifers

Irrigated agriculture in Mediterranean semi-arid regions is increasingly constrained by aquifer depletion and climate change. Enhancing water use efficiency in the irrigation of perennial crops is essential for long-term agricultural sustainability. This study introduces a Spatial Irrigation Adequacy Index (SIAI%), which compares satellite-derived actual evapotranspiration (ETa) with modeled crop water requirements (CWR) at the pixel scale. The framework was applied to assess irrigation performance in grapevine (Vitis vinifera), apple and citrus across three groundwater-dependent systems: Requena-Utiel (Spain), Ain Timguenay (Morocco), and Campina de Faro (Portugal). Actual evapotranspiration was estimated using Landsat 8 and 9 imageries processed with the SSEBop model, while crop water demand was calculated with the FAO-56 dual crop coefficient method incorporating site-specific agroclimatic data. Results revealed distinct crop-specific irrigation patterns: grapevines achieved near-optimal water use, apple orchards were generally over-irrigated, and citrus groves experienced persistent deficits. The framework enables scalable, transferable assessments of irrigation performance, supporting sustainable water management and adaptive irrigation under climate variability.