Abstract:
Irrigation development could improve agricultural productivity and enhance socioeconomic
development of the community. Though agriculture is the leading sector, most of Ethiopia’s cultivated
land is under rain fed agriculture. Rainfall variability and inadequacy have been challenging the
sector due to local and global environmental changes. This study was intended to evaluate suitability
of Walga sub basin for surface irrigation development and producing geo-referenced map of
potentially irrigable sites. Methodology of the current suitability encompasses evaluation of slope,
land use land cover, major soil physical properties and surface water resources of the sub basin for
surface irrigation development. Suitability of the area’s slope, soil, land use land cover and surface
water resources were evaluated and geo-referenced map of each parameter were presented on Arc
GIS. Overall suitability map of the area for the intended irrigation method was produced using
suitability model developed on Arc GIS. In the suitability’s model weighted overlay analysis, high
weight was given for slope, since it is the determinant factor in the evaluation of the given area for
surface irrigation development. Result of the suitability model revealed that about 45.72%
(135519.18 ha) of lands in the sub basin were in the range of highly suitable to marginally suitable
for surface irrigation development due to the combined effect of slope, soil and land use land cover
suitability. Potentially suitable sites for surface irrigation development were evaluated for the
selected crops (Maize, Soyabean and Sesame). By maintaining 20% of the stream flows for
downstream ecological balance, flows in each stream are able to satisfy gross irrigation water
requirements of the selected crops in the potentially irrigable sites. Accordingly; Amanya, Rebu,
Kulit, Nano, Walga and Darge river catchments have a total potentially irrigable areas of 41.32 %
(122488.2 ha) together in the sub basin through surface irrigation system. The current study
considered slope, land use land cover, surface water availability and some soil physical properties
only. Other suitability factors like socioeconomic, environmental issues, soil chemical properties and
others should be studied in detail for sustainable irrigation development in the area.
