Term:
Rainwater harvesting; rainwater collection
Definition:

Rainwater harvesting (RWH) is a method of inducing, collecting, storing and conserving local surface runoff for agricultural production.; Areas where rainwater is collected and either directly applied to the cropped area, and stored in the soil profile for immediate uptake by the crop (runoff irrigation) or stored in a water reservoir for future productive use (for example used for supplementary irrigation). Rainwater harvesting includes: (i) Roof water harvesting is mainly used for domestic purposes and sometimes as water supply for family gardens; (ii) Micro-catchment water harvesting is characterized by a relatively small catchment area C (< 1 000 m²) and cropping area CA (< 100 m²) with ratio C:CA = 1:1 to 10:1. The farmer usually has control over both the catchment area and the target area. These systems are used for the irrigation of a single tree, fodder shrubs or annual crops. The construction is mainly manual. Examples are pits, semi-circular bunds, Negarim micro-catchment, eyebrow terrace, contour bench terrace, etc.; (iii) Macro-catchment water harvesting collects water that flows over the ground as turbulent runoff and channel flow. These systems are characterized by a large catchment area C (‘external' catchment area of 1 000 m² – 200 ha), located outside the cultivated area CA, with a ratio C:CA = 10:1 to 100:1. The systems are mainly implemented for the production of annual crops. The construction is manual or mechanized. Examples are trapezoidal bunds, large semi-circular bunds, stone bunds, etc.

Domain:
Water
Source:
Rainwater harvesting technologies for agricultural production: A case for Dodoma, Tanzania (by N. Hatibu and H. Mahoo), Animal Traction Network for Eastern and Southern Africa (ATNESA) (http://www.fao.org/ag/ags/agse/agse_s/3ero/namibia1/c21.htm).
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