Terry Thomas and Dai Rees
10th International Rainwater Catchment Systems Conference, Mannheim, Germany, 2001
This paper concerns the use of domestic roofwater to supply households in the rural areas of low-income countries. It focuses on communities where rainfall is sufficient, roofing is suitable for domestic roofwater harvesting (henceforth DRWH), and where existing point water sources are so widely spaced that fetching water from them is a considerable household burden. The paper is illustrated by data from East African areas where these conditions apply and where incidentally a very complete evaluation of rural water economics was made in the mid 70s (White, Bradley, & White, 1972 - which showed the over 10:1 increase in per capita consumption that can occur when convenient piped water replaced fetched water).
The primary benefit of DRWH in the scenario we are addressing is the time-saving, or more rarely money-saving, obtained by reducing the fetching of water. A secondary benefit is the increase in water consumption that follows any reduction in marginal water costs. The situation has a strong seasonal aspect, since in the dry season the cost of water from point sources rises, due to the failure of more local sources and increases in queuing times, while the yield of DRWH systems falls. There are consequent changes in water consumption.
The main design choices in DRWH concern the size and type of tank used, the area of roof guttered, the water-management strategy and any phasing of construction. This paper addresses these options mainly from an economic standpoint, using a mixture of field data collected in 2000 and modelling. It is based on activities undertaken under two 4-partner DRWH research programmes (one EU-funded and the other DFID-funded) and under a smaller programme funded by the Laing Trust and by Warwick University. The support of these sponsors is gratefully acknowledged. Further details may be found in Rees & Thomas 2000, DTU website & RHRG website.