Rooftop Rain Water Potential Assessment for Non-domestic Use: A Case of Addis Ababa Science and Technology University

This study investigates the efficacy of rooftop rainwater harvesting (RWH) at Addis Ababa Science and Technology University (AASTU) as a sustainable water and energy conservation strategy. The research aims to optimize water resource allocation by prioritizing harvested rainwater for non-domestic applications, thereby reducing pressure on conventional domestic water supplies. Utilizing ground measurements and ArcGIS spatial analysis, the total rooftop catchment area was quantified as 68,195.74 m². Annual harvestable rainwater potential, derived from Ethiopian Meteorology Agency (EMA) rainfall data (Akaki station), was estimated at 662,273.4 m³. Concurrently, irrigation demand for AASTU’s landscaping—calculated through crop water requirement assessments and standardized crop coefficients was determined to be 184,830.33 m³/year. The results demonstrate a substantial surplus of harvestable rainwater, underscoring RWH’s viability in meeting institutional non-potable demands. These findings advocate for rooftop RWH systems as a critical component of integrated water management strategies, offering a scalable model to mitigate resource scarcity in urban academic environments. The study provides actionable insights for policymakers and institutional stakeholders to advance sustainable water stewardship practices.