61a catchment which produces runoff that collects at the furrow. A cereal crop is
planted on the lower side of the furrow and a pulse on the upper side. The furrows
are tied every 5 m to ensure that, in the case of a defective spirit level, runoff does
not flow laterally and concentrate on one side causing erosion. The technique is,
therefore, suitable in areas with a well-developed use of animal power (Hai 1998 ;
Oweis et al. 2001 ).
4.2.4 Trapezoidal Bunds
This technique is suitable for areas with 250–500 mm of annual rainfall. It consists
of large structures enclosing up to 1 ha and impounding large amounts of runoff
from an external area. Crops are planted in the cropping area enclosed by soil bunds.
The impounding bunds are laid on the contour but staggered down the slope to allow
for the release of excess runoff. Excess runoff is discharged from the tips of the
bunds. The most suitable slopes are 0.25–1.5 % on even topography and non-
cracking soils such as black cotton soil. The maximum bund height is 0.6 m
Fig. 6 Contour ridges: a schematic sketch; combination of shrub and barley in Jordan (bottom left)
and shrub in Syria (bottom right) (Source http://www.ricehub.org/RT/land-development/inland-
valleys/water-control-structure/; Aktar Ali, personal communication)
Water Harvesting in Dry Environments