Investigation on Rooftop Rainwater Harvesting Potential and Roof Catchment Area Measurement Techniques in Addis Ababa, Ethiopia

Abstract

This study was conducted by aiming quantification of the potential of rooftop rainwater harvesting (RT-RWH) in general and (1) comparing alternative methodologies for measuring roof catchment areas, (2) analyzing demand-supply gap between harvested rainwater and toilet flushing water demand in particular for the study area. A comparison was made between the roof catchment area measurement techniques such as; Google Earth (GE), Master Plan and field survey. The coefficient of determination (R 2 ) was used as a comparison tool for deciding which measurement techniques are better, so as to recommend for accurate usages for practical purposes for roof catchments areas measurements. Hence, R 2 values of field measurement versus Master Plan, field measurement versus GE, and Master Plan versus GE were found to be 0.997, 0.959 and 0.971 respectively. In the meantime, it was proved that measuring roof catchment areas by the Master Plan is better than GE for the case of this study area. In addition to this, the water harvesting potential of the study area was estimated and compared with the toilet flushing water demand (which accounts for the major portions of domestic water demand of the study area). The annually harvested rainwater of the study area was estimated to be 1 25,172m 3 and the respective annual toilet flushing water demand was 6,090,314m 3 . This result showed that 18.13% of water consumption of toilet flushing of the study area could be covered by the harvested rainwater, which is an indispensable figure to alleviate and minimize the ever-increasing water scarcity of the study area to some extent. Keywords: Rooftop-Rainwater Harvesting; Google Earth; Field Survey; Master Plan; Potential Assessment DOI: 10.7176/CER/12-8-03 Publication date: August 31 st 2020