Water Harvesting – Guidelines to Good Practice

Construction of the dam wall begins with excavation of a core trench along the length of the dam wall which is filled with clay  and compacted to form a ‘central core’ that anchors the wall and prevents or minimizes  seepage. The upstream and downstream embankments are built using soil with a 20-30% clay content. It is common to plant Kikuyu grass (Pennisetum clandestinum) to  prevent erosion of the embankment. The dam is fenced with barbed wire to prevent livestock from eroding the wall. Typical length of the embankment is 50-100 m with water depth ranging 4-8 m. An emergency spillway (vegetated or a concrete shute) is  provided on either, or both sides, of the wall for safe disposal of excess water above the full supply level. The dam water has a maximum throwback of 500 m, with a capacity ranging from 50,000 – 100,000 m3.
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