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

Yalemzewd Abere Mulu

doi:10.7176/cer/12-8-03

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

Highlights

Sustainable utilization of natural resources and their protection is of fundamental significance for smart development (Urbaniec et al, 2017; Lopez and Roderiguz, 2019)
According to the measurement conducted by Google Earth and Master Plan, 489 buildings were found and buildings of having the same roof shape were categorized into ten groups for the ease of simplicity
Rainwater harvesting system, where rainfall runoff collected and utilized, is a prominent solution to address the issue of water scarcity by conserving the available water resources and the energy needed to deliver water to the water supply system

Summary

Introduction

Sustainable utilization of natural resources and their protection is of fundamental significance for smart development (Urbaniec et al, 2017; Lopez and Roderiguz, 2019). It is very crucial to implement alternative sources of water and energy in all capacities of the economy, in housing, which is characterized by a high demand for water and energy (Stec et al, 2017; Kordana and Slys, 2017). Water resources are affected by climate change and the increase of the urbanization process, which causes substantial hydrological alterations in catchment areas. These alterations have an adverse influence predominantly on the quantity and quality of rainwater, causing an increase in the speed and volume of runoff, a decrease in infiltration, an increased risk of flooding, and the hydraulic overload of sewage systems (Pochwat et al, 2017; Kazmierczak and Kotowski, 2014; Pochwat, 2017)

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