International Rainwater Catchment Systems Conference
Mannheim, Germany - September 2001
Rainwater Catchment in Humid and Arid Regions
Roofwater Catchment for the Rural Poor
Terry Thomas and Dai Rees
Development Technology Unit
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.
PDF of full document (6pp, 42kb)
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