Assessment of Rooftop Rainwater Harvesting as an Alternative Source of Water Supply for Higher Institutes in Ethiopia: The Case of Wachemo University, Main Campus

Rooftop rainwater harvesting has been used worldwide as an alternative source of water supplyWater supply for many people. In view of this, the aim of the study is to assess the potential of rooftop rainwater harvesting as an alternative source of water supplyWater supply for Wachemo University. Twenty years of rainfall data were analyzed to determine the average monthly and annual rainfall potential of the study area. The possible volume of water that could be harvested from selected rooftops at Wachemo University was quantified using the rational method. The Ripple Mass Curve method was also applied to determine the harvestable rooftop rainwater storage capacity for the study area. The water sampling points and building digitization were made using Google Earth and ArcGIS 10.3 tools. The quality of the rooftop rainwater was examined as per the standard method for the examination of water and wastewater quality. The results demonstrated that the maximum amount of water that could be harvested was 102,268 m3 per year from a 107,587 m2 rooftop area with an average annual rainfall of 1188.0 mm. The harvested rainfall from the rooftops could cover approximately 51% of the average annual water demand of the university. The Ripple Mass Curve analysis indicated that storage capacity of 8493.7 m3 was required to harvest rooftop water in the study area. The water qualityWater quality of the rooftop examination was found to be within the permissible limit for drinking water qualityWater quality requirements, except for the bacteriological parameters. The cost analysis demonstrated that a total of 6,937,200 ETB (128,466 USD) was required to install rainwater harvesting systems for 94 buildings inside Wachemo University main campus. The study concluded that rooftop rainwater harvesting is a promising alternative solution to solve the water scarcity problem and ensure a continual source of non-potable water at Wachemo University.