Spatially Distributed Water Balance Modeling Using WetSpass-M for Groundwater Recharge Assessment in the Semi-Arid Al-Haouz-Mejjate Plain, Morocco

¹ International Water Research Institute (IWRI), Mohammed VI Polytechnic University, Ben Guerir, 43150, Morocco,
² Laboratory of geosciences of natural resources, Hydroinformatic section, Faculty of sciences, Ibn Tofail University, Campus Maamora, BP.133, 1400, Kénitra, Morocco

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Abstract

Quantifying groundwater recharge in semi-arid regions is essential for sustainable resource management. This study applies the WetSpass-M model to estimate spatially distributed groundwater recharge, actual evapotranspiration (AET), and surface runoff across the Al Haouz-Mejjate plain (Morocco) from 2009 to 2014. The model integrates climate, land-use, soil, and topographic datasets at 30 m resolution to simulate annual water-balance components. Results reveal strong spatial and temporal heterogeneity. AET is highest in irrigated and densely vegetated zones, while runoff remains low but increases locally on steep or fine-textured soils. Recharge exhibits substantial interannual variability, ranging from 0 mm in drought years to >350 mm during wet conditions. The southeastern alluvial fans consistently emerge as dominant recharge zones, whereas the northern and western basin sectors show persistently low infiltration. Recharge patterns closely track precipitation fluctuations, with marked reductions in 2011-2012 and strong recovery in 2014. These findings emphasize the combined influence of climate, geomorphology, and land-surface characteristics on hydro-logical partitioning in this semi-arid aquifer system and provide a robust framework to support groundwater management and future modeling efforts in the region.