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Natural ground catchment and Open water reservoir

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Since 1967, an estimated US$50 million has been spent on pond/dam construction in East Africa and most of them are now abandoned due to heavy siltation. In Ethiopia, the siltation rate in the southern rangelands was estimated at 1,000/2,400 cubic metres per pond, per year. Local pastoral groups were unable to excavate more than 15 to 20 cubic metres by hand per year.

According to the International Livestock Center for Africa (ILCA), it appears possible to construct small to medium-sized ponds and to maintain or enlarge existing ones using ox-drawn scoops and ploughs. In an experiment, ILCA researchers used five metal scoops with a capacity of 0.2 cubic metres each. They were made in Ethiopia at a cost of US$150 each. Six ploughs of the local "Matesha" design-a simple ox-drawn aid - were also used.

The oxen worked in pairs for five hours a day. Two pairs were used in two shifts every day. They were fed two kgs daily of a mixture of bran and oilseed cake (noug) and grazed for seven hours. The feeding of concentrates was considered necessary because drought had reduced grass cover to a minimum. All oxen were watered every three days, which is a common practice. Seven ponds were excavated in 81 days. The amount of silt taken away totaled 3,254 cubic metres. The average volume of silt excavated per ox-pair per day was 13 cubic metres in 62 loads. The cost of excavation by scoop totaled US$ 0.30/0.40 per cubic metre. Excavation costs using heavy earth moving machinery were about US$2.00 to US$3.00 per cubic metre.

Winona

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