Roofwater harvesting can be a clean and convenient method of obtaining water. Terry Thomas considers the many advantages and disadvantages of its use, as well as its future prospects.
In few areas of Africa is roofwater harvesting likely to be sufficient for all domestic needs, at a reasonable cost. But despite this and other factors that have so far prevented the widespread dissemination of this technology, roofwater harvesting is gradually being recognized as a partial solution to the need for clean water, close to the home.
Many tropical countries often have poorly performing or absent piped-water supplies in their rural and suburban areas. Fetching water from point sources such as wells is often arduous and such sources are vulnerable to pollution. Domestic roofwater harvesting (DRWH in this article) is a promising alternative self-supply technology and is supported by many agencies and associations. However take-up of DRWH has been very limited due to the six constraints discussed in this article. These are: inadequacy of annual roof run-off volume; excessive cost; difficulty of water management; uncertain water quality; poor installation/maintenance/longevity; and ugliness. While these constraints rule against DRWH becoming a universal first choice for less economically developed countries, (LEDC) domestic water supply, there are many specific scenarios where it outperforms, or is cheaper than, the alternatives. The paper identifies some of these scenarios and also how the constraints can be minimized by prudent application and ongoing R&D.