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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #335475
Title: Evaluating erosion control practices in an actively gullying watershed in the highlands of Ethiopia

Author
item AYELE, GETANEH - Bahir Dar University
item ADDISIE, MESERET - Bahir Dar University
item Langendoen, Eddy
item TEGEGNE, NIGUS - Bahir Dar University
item TILAHUN, SEIFU - Bahir Dar University
item MOGUS, MAMARU - Bahir Dar University
item NICHOLSON, CHARLES - Pennsylvania State University
item STEENHUIS, TAMMO - Cornell University

Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2018
Publication Date: 10/7/2018
Citation: Ayele, G.K., Addisie, M.B., Langendoen, E.J., Tegegne, N.H., Tilahun, S.A., Mogus, M.A., Nicholson, C.F., Steenhuis, T.S. 2018. Evaluating erosion control practices in an actively gullying watershed in the highlands of Ethiopia. Earth Surface Processes and Landforms. 43(13):2835-28-43. DOI: 10.1002/esp.4436.

Interpretive Summary: Long-term watershed studies in the sub humid northern Ethiopian highlands, which have been devastated by extensive gully networks, have shown that conventional soil and water conservation practices (SWCPs), such as check dams and soil bunds, are unable to reduce downslope and downstream sediment concentrations. During 2013 and 2014 scientists at the USDA-ARS National Sedimentation Laboratory in collaboration with researchers at Bahir Dar University (Ethiopia), Cornell University and Penn State University have investigated the effectiveness of the Ethiopian government-mandated conventional SWCPs and community-participatory gully rehabilitation in the Ene-Chilala watershed located south of Lake Tana, Ethiopia. Suspended sediment concentration and flow discharge were measured at the watershed outlet and at two nested upslope watersheds. Upland rill erosion on plowed land early in the rain phase and gully erosion in saturated valley bottoms were main sources of sediments in the rivers. The combination of decreased runoff due to less rainfall and participatory rehabilitation of active shallow gully heads and bank protection placement were responsible for the reduced sediment loads in 2014 compared to 2013. The study is important for farmers, soil conservation experts and policy makers in order to inform future land management activities.

Technical Abstract: Soil erosion, with significant contributions from gullies, is a serious problem in the Ethiopian highlands. Conventional top-down erosion control approaches have not reduced sediment loads in rivers. The objective of this paper is to examine patterns of discharge and sediment transport, and to provide an initial assessment of whether soil and water conservation practices (SWCP) can reduce sediment loads. The study was conducted during 2013 and 2014 in the 414 ha Ene-Chilala watershed with a unimodal sub-humid monsoon climate. In 2013 and 2014, as part of the government large-scale soil and water conservation program, the local community was mandated to install upland infiltration furrows and subsequently, farmers, by their initiative, rehabilitated six gully heads and protected 16 m of eroding stream banks. Suspended sediment concentration and flow discharge were measured at the watershed outlet and at two nested upslope watersheds. Precipitation during the 2013 rainy monsoon phase was 1047 mm and 770 mm in 2014. Measured median infiltration capacity was always greater than the rainfall intensity in the unsaturated uplands. After 175 mm cumulative rainfall, the groundwater table reached the surface in the valley bottoms, restricting infiltration, and runoff was generated as saturation excess overland flow and flowed through active gullies out of the watershed. The total annual runoff, including baseflow at the watershed outlet, was 748 mm (2013) and 378 mm (2014). Upland rill erosion on plowed land early in the rain phase and gully erosion in saturated valley bottoms were main sources of sediments in the rivers. Average annual sediment yield at the outlet of the watershed was 75 t ha-1 y-1 in 2013 and 10 t ha-1 y-1 in 2014. The combination of decreased runoff and participatory rehabilitation of active shallow gully heads and bank protection placement were responsible for the reduced sediment loads in 2014.