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Rainwater harvesting
General features
The distance between barriers or trenches, their size, grade, etc., depend primarily on soil and subsurface conditions, which can vary considerably from place to place. One of the prime factors determining the applicability of these techniques is the slope of the area. Areas having slope greater than 5% are not recommended. Another factor is the soil. If the rainfall is less than infiltration rate in sandy soil, then the technique cannot be applied. Regular maintenance of schemes is required to prevent breaching of barriers and loss of permeability in trenches.
Although small-scale runoff collection activities can be organized on an individual farm basis in some locations, where many farms are found on steep slopes, effective programs will require an organized community effort, possibly with NGO assistance. In the past some large scale runoff collection and soil protection programmes have been initiated and funded by governments and international donors.
Advantages of ground surface runoff collection systems are that they prevent soil erosion as well as recharging the groundwater. Also systems collecting surface runoff from fields are cheap and easy to construct. However, the volumes of recharged water are relatively small, and benefits may not be visible for years.