Augmenting rural water supply by rooftop rainwater harvesting in Egbeada, Imo State, Nigeria

Abstract

This study was carried out to evaluate the water yielding potentials of existing roof catchments of residential and public buildings in Egbeada, Imo state, Nigeria and to determine the optimum volume of storage to satisfy demand at both household and multi-household levels. The potential of the community for rainwater harvesting was assessed by subjecting 20 years of rainfall data to descriptive statistical analysis and application of appropriate mathematical formulae to calculate available roof areas, design population and water demand. Mass curve analysis and SimTanka simulation model were used to determine the optimum storage to satisfy water demand at the levels considered. The results of the statistical analysis shows that there is a much lower risk that rainwater harvesting will not meet the minimum water demand of the community.  The mass curve analysis shows that monthly demands of 6 m³ (25l/p/d), 8.4 m³ (35l/p/d) and 9.6 m³ (40l/p/d) can be met from tank storages of 25 m³, 41 m³ and 44.4 m³, respectively at individual household level. The SimTanka simulation result shows that at individual level, when practiced as a complete water source, a daily water demand of 40l/p/d can be satisfied optimally at 99.8% from a storage of 63.5 m³ all year round and if practiced as a partial water supply option(only during the dry season) a daily water demand of 60 l/p/d can be satisfied 100 % of the time from rain water storage of 65.5 m³.However, at multi-household level  only a daily demand of 15l/p/d can be satisfied at 100% of the time from a storage of 7,200 m³. Greater potential exists for rooftop rainwater harvesting at the individual household level than at the multi - household level in Egbeada community.