Siltation of dam reservoirs poses a significant challenge to water resource management worldwide, especially in the Mediterranean basin. Within the Moroccan context, where updated data regarding the siltation of dam reservoirs and their temporal evolution are lacking, this study introduces research focusing on developing siltation models for Moroccan dams. Employing Geographic Information System (GIS) technology, we aim to scrutinize sediment deposition’s spatial distribution and temporal changes within dam reservoirs. This endeavor constitutes a segment of our comprehensive quantitative and qualitative investigation into the silt accumulation within Moroccan dams, exploring potential industrial applications of the retained sediment. The methodology encompasses gathering historical data on dam siltation from diverse sources, encompassing government archives and antiquated cartographic surveys. The collected and updated data pertain to 60 large dams, which collectively account for more than 92% of the storage capacity of all major dams in Morocco. Thanks to the developed GIS application, collected bathymetric data has allowed the evaluation of reservoir siltation. These data have been organized and represented in spatial maps and temporal curves. This representation on an interactive map made it possible to identify the regions strongly affected by the dams’ siltation and observe the changes over time. This analysis reveals the impact of siltation on Morocco’s watersheds, with a notable emphasis on the Moulouya River basin in the northeast, where reservoirs exhibit the highest levels of silt accumulation. We attribute the prevalence of this phenomenon to the soil composition, which comprises 35.5% unstable quaternary formations, and the arid to semi-arid climate, which restricts the growth of dense vegetation. The intensity of rainfall, steep slopes, and deforestation, in addition to the previous factors, favor soil erosion and sedimentation. This research significantly enhances our comprehension of siltation patterns in large dam reservoirs across Morocco by concentrating on the innovative integration of bathymetric techniques with GIS technologies. These findings are paramount for decision-makers and water resource managers, providing indispensable insights crucial for strategic planning and the effective implementation of siltation mitigation measures.