Nature based stormwater management for annual retention and water quality in Sharjah, United Arab Emirates: an InVEST assessment

Abstract

Rapid urbanization and climate change are altering stormwater dynamics in arid cities, where limited rainfall, high evapotranspiration, and water scarcity amplify the challenges of management. Traditional gray infrastructure is costly and often insufficient to address flooding and water quality concerns. Ecosystem-based approaches that emphasize stormwater retention, infiltration, and pollutant reduction offer sustainable alternatives; however, empirical evidence from Gulf cities remains limited. This study applied the InVEST Urban Stormwater Retention model to quantify hydrologic, water quality, and economic services in Sharjah, United Arab Emirates. Using high-resolution Sentinel-2 land use and land cover (LULC) data, gridded precipitation, hydrologic soil groups, and road networks, the model estimated annual stormwater retention, runoff, recharge, avoided pollutant loads, and replacement costs. The results indicate that approximately 80% of annual precipitation is retained within the landscape, while approximately 20% becomes surface runoff. Potential groundwater recharge was estimated separately at approximately 5% of annual precipitation and represents a component of retained precipitation rather than an additional water-balance fraction. An illustrative replacement-cost benchmark indicates that reproducing this retention capacity solely through engineered storage could require substantial capital investment. The findings indicate the disproportionate role of vegetated and agricultural lands in delivering stormwater services, in contrast to impervious urban areas, which contribute little to retention. The results provide evidence for integrating nature-based solutions into Sharjah’s stormwater planning, thereby supporting water security, climate resilience, and sustainable urban development in arid regions. Compared with conventional event-based hydrologic models and gray infrastructure–focused approaches, this ecosystem service–based assessment offers a long-term, spatially explicit, city-scale evaluation of stormwater regulation, water quality protection, and economic benefits. The findings support the integration of nature-based stormwater solutions into urban planning to enhance water security, climate resilience, and sustainable development in arid regions.