Dynamics of Soil Erosion as Influenced by Watershed Management Practices: A Case Study of the Agula Watershed in the Semi Arid Highlands of Northern Ethiopia
Since the past two decades, watershed management practices such as construction of stone bunds and establishment of exclosures have been widely implemented in the semi arid highlands of northern Ethiopia to curb land degradation by soil erosion. This study assessed changes in soil erosion for the years 1990, 2000 and 2012 as a result of such watershed management practices in Agula watershed using the Revised Universal Soil Loss Equation. The Revised Universal Soil Loss Equation factors were computed in a geographic information system for 30 x 30 m raster layers using spatial data obtained from different sources. The results revealed significant reduction in soil loss rates by about 55 from about 28 to 12 t ha 1 per year in 1990 2000 and an overall 64 reduction from 28 to 10 t ha 1 per year in 1990 2012. This change in soil loss is attributed to improvement in surface cover and stone bund practices, which resulted in the decrease in mean C and P factors, respectively, by about 19 and 34 in 1990 2000 and an overall decrease in C factor by 29 in 1990 2012. Considerable reductions in soil loss were observed from bare land (89 followed by cultivated land (56 and shrub land (49 Furthermore, the reduction in soil loss was more pronounced in steeper slopes where very steep slope and steep slope classes experienced over 70 reduction. Validation of soil erosion estimations using field observed points showed an overall accuracy of 69 which is fairly satisfactory. This study demonstrated the potential of watershed management efforts to bring remarkable restoration of degraded semi arid lands that could serve as a basis for sustainable planning of future developments of areas experiencing severe land degradation due to water erosion.
Environmental Management