Multi-criteria based Watershed Prioritization for Soil and Water Conservation: The case of Gotu Watershed, Awash River Basin, Ethiopia
Background: In Ethiopia, soil and water conservation has often been implemented haphazardly through community mobilization during dry seasons. However, in the process, the question “which part of the watershed should be conserved first considering different criteria and which one should be the last?” is never been answered.
Objective: This study was undertaken to prioritize sub-watersheds on the basis of myriad of parameters: morphometric, soil loss, socioeconomic and related criteria for soil and water conservation activities in five catchments in Gotu watershed, Awash River basin, Ethiopia.
Materials and Methods: Advanced Space borne Thermal Emission and Reflection Radiometer Digital Elevation Model, Revised Universal Soil Loss Equation (RUSLE), socioeconomic and related data like population density, share of cultivated land, economic status, land pressure, potential labor force for conservation, conservation work performance, and share of unirrigated land were used for prioritization exercise.
Results: It was found that Gotu watershed has seven order streams with a mean bifurcation ratio of 2.1; higher stream frequency = 6.4–7.9 streams km–2; low drainage density (0.52–2.85 km km–2) and moderate drainage texture (3.7–5.7); elongated shape (Form factor = 0.16–0.23; elongation ratio = 0.45–0.53; circulatory ratio = 0.17–0.24). Using RUSLE model, the soil loss of the study catchments ranged from 0 t ha–1yr–1in the plain area up to 197.2 t ha–1 yr–1 in the steeper, and fragile part of the watershed which made catchment two an area of severe soil erosion. Considering socioeconomic parameters, catchment five and catchment two have been shown with low and high status, respectively. Therefore, the combined result showed that catchment five that measures about 17.77 km2 out of 160.56 km2 of the total area of the study watershed requires the first priority for soil and water conservation measures.
Conclusion: It is concluded that catchments with high soil loss may not usually guarantee primary attention for conservation unless the condition of socioeconomics, morphometry of catchments and related parameters simultaneously contribute to the decision-making process of conservation planners. This implies that land conservation planners should reconsider prioritization criteria of resource flows to soil and water conservation initiatives.