Water scarcity represents a critical challenge for sustainable urban development in hyper-arid environments, where rapid demographic growth and socioeconomic expansion intensify pressure on limited water resources. This study develops a spatially explicit application of the Water Evaluation and Planning (WEAP) system to assess long-term urban water demand dynamics in Tamanghasset, southern Algeria, a groundwater-dependent Saharan city characterized by extreme climatic constraints and infrastructure limitations. Unlike conventional basin-scale WEAP applications, the proposed framework integrates intra-urban modelling across fifteen sectors and adopts a static supply assumption to isolate structural demand-driven vulnerabilities under constrained water availability. Water demand was simulated for the period 2020-2060 using contrasted planning scenarios combining demographic growth rates (1.1% and 3.2%) and per capita service levels (60, 120, and 150 L/person/day), consistent with national demographic trends and international water service benchmarks. Results indicate substantial divergence among scenarios. Under the reference service level (120 L/person/day), total demand increases from approximately 9.8 Mm & sup3; in 2020 to 50.6 Mm & sup3; by 2060, significantly exceeding the current supply capacity of about 11.8 Mm & sup3;/year. Even under conservative assumptions, demand growth leads to persistent structural deficits, while high-growth scenarios produce severe imbalances. Spatial analysis reveals that densely populated sectors, including Guet-el-Oued, Tahaggart Ouest, Sersouf, and Sorou, consistently emerge as demand hotspots, highlighting pronounced intra-urban inequalities. The analysis emphasizes that projected deficits arise primarily from structural demand dynamics rather than short-term variability. Results should therefore be interpreted as scenario-based planning insights rather than deterministic forecasts, acknowledging uncertainties associated with demographic projections and allocation assumptions. The findings demonstrate the value of WEAP as a decision-support framework for Integrated Water Resources Management (IWRM), supporting proactive strategies such as efficiency improvements, demand management, wastewater reuse, and diversification of water supply options to enhance long-term resilience in hyper-arid urban systems. [GRAPHICS]