Assessing the effects of land uses and water conservation on soil erosion in central Ethiopia
Land degradation in the form of soil erosion has significant direct effects on farmlands resulting from soil loss and indirect effects away from farms such as siltation of reservoirs, irrigation canals, and flooding. In Ethiopia, land degradation has affected national agricultural production and undermined the implementation and success of sustainable intensification. Due to land mismanagement, Ethiopia experiences the worst soil erosion in the world.
To tackle the problem of soil erosion and moisture stress, the government of Ethiopia introduced a yearly mass campaign where communities get together and implement various soil and water conservation practices. Although the interventions are believed to have reduced soil erosion and enhanced surface and groundwater recharge, quantitative information on the impacts of various options at different scales is scarce.
A recent study led by Africa RISING in collaboration with the International Center for Tropical Agriculture (CIAT), the International Livestock Research Institute (ILRI) and other CGIAR scientists filled the gap of the scarce quantitative information. The study assessed the impacts of different land uses, soil and water conservation (SWC), and suspended sediment yield interventions in the central highlands of Ethiopia. Standard erosion plot experiments and hydrological stations were used to monitor the daily water and suspended sediment yield from 2014 to 2017. The assessment was conducted in Jemma River subbasin of the Blue Nile in Basona Worena District.
The results of the study show differences between treatments both at plot and watershed scales. Runoff and soil loss were reduced by an average 27 and 37%, respectively due to SWC practises at the plot level. Overall, SWC practises implemented at the watershed level reduced sediment yield by about 74% (in the year 2014), although the magnitude of sediment reduction due to the SWC interventions reduced over time. At both scales it was observed that as the number of years since SWC measures have been in place increased, their effectiveness declined due to the lack of maintenance. This study also revealed that extrapolating plot data to watershed scale causes overestimation or underestimation of net erosion.
Africa RISING, one of the research-for-development projects in Ethiopia, is generating evidence to support Ethiopia’s government watershed management initiatives across different agro-ecologies.