Review of Rainwater Harvesting Techniques and Evidence for their Use in Semi-Arid Tanzania

Rainwater harvesting (RWH) should be regarded as a continuum of techniques that link in-situ soil-water conservation at one extreme to conventional irrigation at the other. In-situ RWH, com-prises a group of techniques for preventing runoff and promoting infiltration. Micro-catchment RWH comprises a group of techniques for collecting overland flow (sheet or rill) from a catchment area and delivering it to a cropped area in order to supplement the inadequate direct rainfall. The transfer normally occurs over a relatively short distance entirely within the land-holding of an individual farmer and the system is therefore sometimes known as an "internal catchment".. Macro-catchment RWH comprises a group of techniques in which natural runof is collected from a relatively large area and transferred over a longer distance. Examples of each of these catego-ries of RWH exist in parts of Tanzania, but their potential is largely neglected by research and extension services and they are under-exploited. The purpose of this paper was to assess the extent to which the different rainwater harvesting systems, are used in Tanzania. The findings show that there is a widespread practice of rainwater harvesting in Tanzania. Rainwater harvesting with storage of water for livestock has received government support in the past. However, many stor-age reservoirs have been destroyed by siltation. On the other hand rainwater harvesting for crop production has not received an adequate support from research and extension services. Therefore, although farmers are practicing rainwater harvesting, they are faced with shortage of appropriate technologies and knowledge