Abstract:
The world water demand is growing twice as fast as the population. On the other hand, Food
supply is the greatest challenge faced by humankind in the 21st century. The communities in the
study area are facing acute water shortage for crop production during dry seasons, where
Rainwater harvesting is vital means of survival. The purpose of this study was to assess water
harvesting zone for irrigation practices by considering socioeconomic and biophysical factors.
This was performed through integrated Geographic Information Science, Soil Water
Assessment Tool model, fuzzy logic, and Analytical hierarchy process model. The parameters
used for rainwater harvesting site selection were rainfall, drainage density, surface runoff,
percentage of clay content, land use land cover, slope, lithology, lineament, and Euclidean
distance to settlement and road. The Soil Water Assessment Tool model was used to compute
run-off, Analytical hierarchy process was used to drive the weight of each influential factor,
fuzzy membership to standardize the input factor, and gamma fuzzy overlay weighted was used
to aggregate factors together. Statistical performance of the Soil Water Assessment Tool model
was revealed with R2
of 0.79 and NSE of 0.77 for monthly calibration and R2
of 0.81 and NSE of
0.75 for monthly validation periods. Rainwater harvesting potential suitability class coverage
of the study area was very highly Suitable (16.91%), highly suitable (27.6%), moderately
suitable (20.23%), low suitable (13.1%), not suitable (6.43%), and constraints (15.73%).
Finally, surface irrigation land suitability class coverage was highly suitable (7.8%),
moderately (22.8%), marginally (58.6%), and unsuitable (10.8%). The study result could assist
policy makers for better decisions during development of irrigation projects in the Keleta
watershed and for better identification of profitable and sustainable irrigation investment
opportunities in the watershed
