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Main characteristics, benefits an disadvantages

Main characteristics

  • overland flow or rill flow harvested
  • diverted from hillsides, pasture land, forests or roads and settlements
  • runoff usually stored in the soil or in storage facilities
  • catchment usually 30: 200 meters in length
  • size of catchment from 0.1: 200 ha
  • catchment: application area ratio 10:1 100:1
  • runoff coefficient relatively low: 0.1 to 0.5 (10 – 50% of annual rainfall); the longer the catchment the lower the coefficient
  • provision for overflow of excess water
  • cropping area terraced on slopes or in flat terrain
  • suitable for annual and perennial crops tolerant of temporary waterlogging or rapidly maturing on residual moisture
  • nutrients harvested from accumulated sediments and washed-in animal droppings
  • no control over catchment area because located outside farm boundaries

Main benefits

  • Improved crop yields
  • Improved year-round access to water for domestic and livestock consumption, as well as for supplementary irrigation
  • Reduced risk of crop failure by bridging prolonged dry periods and as such contribute to food security and climate change adaptation.
  • Reduced damage from soil erosion and flooding by storing excess runoff water

Main disadvantages

  • Open and shallow rainwater ponds and dams may dry out after the rainy seasons, as the water is lost via seepage (except for rock catchment and sand dams) and evaporation
  • Health risks: open storage structures can be contaminated by animals and can provide a breeding ground for disease-carrying insects. Sand dams are often contaminated as they are seldom protected from animals

(Mekdaschi & Liniger 2013, Critchley & Siegert 1991, African Development Bank 2009, Liniger et al. 2011, Critchley & Gowing 2012, Oweis et al. 2012)