This study aims to identify the most suitable locations for rainwater harvesting (RWH) in the Tafrata Plain, a semi-arid region of northeastern Morocco, to support sustainable agricultural development and optimize water resource management. Recognizing the pressing challenges of water scarcity and uneven rainfall distribution, the research adopts a comprehensive spatial multi-criteria decision-making approach, integrating the Analytic Hierarchy Process (AHP) with Geographic Information Systems (GIS) to systematically evaluate key environmental and socio-economic factors influencing site suitability. The study combines expert knowledge, field observations, and a thorough review of recent literature to select six primary criteria—rainfall, slope, soil type, drainage density, land use/land cover, and distance to roads—and assigns weights to each based on their relative hydrological and operational significance. High-resolution spatial datasets, including Digital Elevation Models (DEM), rainfall records, soil surveys, and remote-sensing-derived land use data, were processed and analyzed in ArcGIS to generate reclassified thematic maps, which were subsequently integrated using the Weighted Linear Combination (WLC) method. The analysis reveals that moderately suitable zones dominate the study area, covering approximately 80.7% of the total surface, while highly suitable and very highly suitable zones represent 9.3% and 4.9%, respectively. Validation of the model against existing in-field water harvesting structures demonstrates that 99% of operational installations coincide with areas classified as very suitable, confirming the accuracy and reliability of the proposed methodology. Despite limitations related to data resolution and the inherent variability of semi-arid climatic conditions, the results provide a scientifically robust and transferable framework capable of guiding medium- and long-term agricultural and water resource planning. The approach allows for informed prioritization of RWH interventions, minimizes risks associated with site selection, and enhances the potential for sustainable agricultural productivity in water-scarce environments. The originality of this study lies in its integrated application of AHP-GIS techniques tailored to semi-arid plains, offering a replicable model for similar regions facing hydrological constraints, and demonstrating a practical balance between scientific rigor and actionable planning.