Assessing Rainwater Harvesting as an Alternative Source of Non-Domestic Water Supply: The Case of Gurgade Condominium, Hosanna

Abstract

Rainwater harvesting and utilization systems have been in place for centuries. Rainwater harvesting refers to the practice of collecting rainwater from rooftops, land surfaces, or rock catchments and storing it for human use. Hosanna Water and Sewerage Enterprise is the only organization responsible for the distribution of water for the town. Gurgade condominium site residents are facing a big challenge due to the water shortage problem. Therefore, the objective of this study is to assess rainwater harvesting as an alternative source for non-domestic purposes in Hosanna Town Gurgade condominium site. The data used for this study was secondary. Data required, such as previous water consumption, area of the roofs, rainfall data, population and runoff coefficient was collected from Hosanna Water and Sewerage Enterprise, National Metrological Service Agency, Hosanna Land Information Center, Hosanna Town Municipality and Central Statistics Agency. Precipitation data for Gurgade condominium was used to determine the amount of water that can be collected. Calculations of the harvesting areas (areas of the rooftop of the blocks) were made by using AutoCAD software from the cadastral map of Hosanna Town. And also the data was collected by personal observations. The built up area of the study was 1536 m2 that can be convenient for rainwater collection. The buildings was composed of 4 blocks (the total area of 1 block was 280 m2 ) and 2 communal blocks with each a total area of 208 𝑚2 . From the area of rainwater harvesting 1069.95 𝑚3 of water will be collected in a year but this will satisfy only 45.6 % of the total non-domestic water demand. Accordingly, from the result providing a collecting ground storage reservoir of 67.74 𝑚3 near the buildings was needed. It was also tried to design the rainwater harvesting components based on design criteria. Based on the design and analyses performed, it becomes clear that rainwater harvesting is not the only solution that will solve all water scarcity issues in Gurgade. Rainwater harvesting can be an alternative solution to support the increasing water demand and reduce the surface runoff as a best management practice which helps to satisfy environmental sustainability which is one of the millennium development goals.