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Large semi-circular or trapezoidal bunds

Large semi-circular or trapezoidal bunds consist of earthen bunds facing up the slope and are built in long staggered rows. These structures harvest runoff water from external catchments upslope and are used for annual and perennial crops as well as pastures. A trapezoidal bund consists of a base bund, connected to two side bunds at an angle of about 135° and a distance between the tips of 10 – 100 m. Overflow is discharged around the tips of the side bunds. The wings of the side bunds are preferably reinforced with stones. Often they are constructed using machinery. Enclosed areas can reach 1 ha in size (C:A 15:1 – 100:1). The technology is suitable for areas with 200 – 400 mm of annual rainfall. Crops are planted when the water trapped in the enclosed area subsides. This technology is relatively new. Semi-circular bunds are suitable for areas with an annual rainfall of 400 mm and hence the C:A ratio ranges between 15:1 – 40:1. In Tunisia large semi-circular bunds are also called tabia. (Mekdaschi & Liniger 2013)