Low-cost roofwater harvesting in the humid tropics

Domestic roofwater harvesting is a centuries-old technique. In the latter half of this century, domestic rain-water, or roof-water harvesting (DRWH) has been promoted mainly in arid areas, where the alternative water sources are scarce and/or prohibitively expensive. It is a technology that is now employed primarily when other conventional options have been discarded due to complexities or cost, or where subsidies are applied for specific promotion of DRWH. In this paper we will consider the use of domestic roofwater harvesting in humid tropical areas of the world. It is demonstrated that the uptake of this technology in areas with favourable climatic conditions, and where users are willing to modify their behaviour, can bring sufficient quantities of clean water to large numbers of people for a large part of the year, without the usual prohibitive initial costs. Firstly, we will consider the climatic implications on DRWH and see what effect preferential rainfall patterns can have on the cost of the DRWH system, especially the cost of water storage. Secondly, we will consider user patterns and show how suitable user behaviour (consumption pattern) can again improve the desirability of a DRWH system. Finally we will look at the work being done at Warwick University (and by other members of the Roofwater Harvesting Research Group) on reducing costs of roofwater collection systems and improving the quality of stored rainwater for use in high rainfall areas.