Rainwater harvesting

Overview

Rainwater harvesting on a commercial farming shed. Picture used courtesy of Helen Gordon, WWF-SA.

Rain water harvesting (RWH) is increasingly being accepted as a practical method of providing both irrigation and potable water in agricultural and development projects throughout the world.

Enough rain falls on the African continent to supply the water needs for 13 billion people, twice the current world population. However, little of the rainfall is collected or stored through sustainable methods, such as small and large-scale rainwater harvesting.

In South Africa, where the backyards of rural homesteads add up to a whopping 200 000 hectares (i.e. double the current area under smallholder irrigation), the potential impact on food security is more than significant.

The level of economic activity has been shown to double in rural villages with access to more water. This has a direct impact on poverty. Every household with a roof can potentially harvest and store rainwater.

RWH has wide application also in urban and peri-urban areas where the quantity, reliability and quality of piped water are sometimes questioned. Some rainwater might require treatment before it is considered suitable for drinking. So-called “appropriate technology” methods (e.g. as solar water disinfection) provide low-cost disinfection options for treatment of stored rainwater for drinking.

Source: UN Environment Programme (UNEP) “Environmental Food Crisis” report, May 2009. Find it at www.unep.org; http://en.wikipedia.org/wiki/Rainwater_harvesting; Tsepho Khumbane, Trustee of The Mvula Trust (adapted)

Contents

Role players
Websites and publications

Role players

Rainwater for drinking should be carefully stored and treated prior to consumption. Several technologies exist for home treatment including: ozone sterilisation, UV, distillation. Fairly simple sand filters followed by household chlorine may also be utilised.

For further details, contact Dr Jo Burgess at the Water Research Commission (RWH for domestic use) or Dr Sylvester Mpandeli (for agricultural use).

Websites and publications

  • Find information and publications at http://amanziforfood.co.za.
  • Various reports on in-field rainwater harvesting and conservation are available from the Water Research Commission. Visit www.wrc.org.za.
  • Kejafa Knowledge Works stocks the publication Water Harvesting Techniques. Contact them at 014 577 8006 or visit www.kejafa.com.
  • www.harvesth2o.com – the “online rainwater harvesting community” (USA based)
  • Find the Info Pak “Collecting rainwater from your roof” from DAFF under the “Resource centre” option at www.daff.gov.za.
  • Contact the Environmental Monitoring Group (EMG) for the DVD “Rainwater harvesting – An illustration of what can be done, and is being done at a community level”. See www.emg.org.za.
  • “Hoops” are raised earth structures (bunds) constructed as semi-circles on gently sloping land. They are made so that the tips of the bunds or hoops point up the slope and are on the same level with the contour line. The hoops capture rainwater that runs down the slope. Rainwater Harvesting for Increased Pasture Production, CTA Practical Guide Series No 3, an equivalent of the South African Info Paks, is a brochure dealing with the making of these hoops. Visit www.cta.int.

Further excellent sources include:

  • Botha, J.J., van Rensburg, L.D., Anderson, J.J., Hensley, M., Macheli, M.S., van Staden, P.P., Kundhlande, G., Groenewald, D.C., & Baiphethi, M.N. 2003. Water conservation techniques on small plots in semi-arid areas to enhance rainfall use efficiency, food security, and sustainable crop production. Report No. 1176/1/03, Water Research Commission, Pretoria.
  • Hensley, M., Botha, J.J., Anderson, J.J., Van Staden, P.P. & Du Toit, A. 2000. Optimising rainfall use efficiency for developing farmers with limited access to irrigation water. Report No. 878/1/00, Water Research Commission, Pretoria.
  • Kundhlande, G., Groenewald, D.C., Baiphethi, M.N., Viljoen, M.F., Botha, J.J., Van Rensburg, L.D., Anderson, J.J. 2004. Socio-economic study on water conservation techniques in semi-arid areas. Report No. 1267/1/04, Water Research Commission, Pretoria.
  • Water resources management in rainwater harvesting: An integrated systems approach includes case studies of villages / farm workers who catch rainwater for a variety of purposes.
  • Rainfed Farming Systems (eds Tow P, Cooper I, Partridge I, Birch C). Springer, The Netherlands. Find the chapter “Rainfed farming systems in South Africa” by Hardy MB, Dizba L, Kilian W and Tolmay J.
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