The potential of rainwater harvesting: the case of the city of Windhoek, Namibia

Windhoek, Namibia’s capital, has experience for more than 25 years of novel approaches in integrated water management largely driven by the scarcity of water in the area. Notably absent in their approaches however, is the rooftop rainwater harvesting which is regarded as one of the viable alternative sources of water for domestic use. This paper assesses the potential economic benefits for rooftop rainwater harvesting for the City of Windhoek. The rooftop areas from four representative formal suburbs of Okuryangava (low income) in the north, Academia (middle income) in the south-central, Pioneers Park (middle income) in the south-west and Ludwigsdorf (high income) in the east, were estimated from high resolution satellite images captured from Google Earth. These estimates were used to extrapolate for the potential amount of rainwater that can be harvested in an average rainy season (i.e. December to April) in the study area. The estimated harvestable amount for each residential area was developed using a simple model that incorporates total rooftop area and estimated rainwater. The derived figure was then expressed in terms of cost per unit prices charged by the City of Windhoek.

Pioneers Park attests to have the highest (134 m3) potential harvestable rainwater per household, while Okuryangava is estimated to harvest the least amount of 36 m3 per raining period. Given the high density of erven, however, Okuryangava has a potential to harvest approximately 920484 m3 of water per hectare, ranking this suburb second after Academia, which stands at 1120716 m3. This is a significant amount of water effectively taken from rainwater rooftop that could also provide justifiable saving to residents if used instead of tap water. It is therefore recommended that the City of Windhoek actively promotes rooftop rainwater harvesting for the benefit of residents and also as a measure to reduce storm-water runoff due to urban development.

Keywords: City of Windhoek, Rooftop Area, Rainwater Harvesting, Water Saving Cost.

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Details

Publication Type Journal article
Publisher Science Publishing Group
Year 2013
Author(s) Festus Panduleni Nashima, Inekela Iiyambo, Johannes Hambia, Martin Hipondoka
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