Improving efficacy of landscape interventions in the (sub) humid Ethiopian highlands by improved understanding of runoff processes

Authors: TEBEBU, TIGIST - Cornell University; STEENHUIS, TAMMO - Cornell University; DAGNEW, DESSALEGN - Bahir Dar University; GUZMAN, CHRISTIAN - Cornell University; BAYABIL, HAIMANOTE - Cornell University; ZEGEYE, ASSEFA - Cornell University; Collick, Amy; LANGAN, SIMON - International Water Management Institute, East Africa And Nile Basin Office; MCALLISTER, CHARLOTTE - International Development Research Centre; Langendoen, Eddy; YITAFERU, BIRRU - Amhara Regional Agricultural Research Institute; TILAHUN, SEIFU - Bahir Dar University

Submitted to: Frontiers in Earth Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2015
Publication Date: 9/2/2015
Publication URL: https://handle.nal.usda.gov/10113/5763090
Citation: Tebebu, T.Y., Steenhuis, T.S., Dagnew, D.C., Guzman, C.D., Bayabil, H.K., Zegeye, A.D., Collick, A.S., Langan, S., Mcallister, C., Langendoen, E.J., Yitaferu, B., Tilahun, S.A. 2015. Improving efficacy of landscape interventions in the (sub) humid Ethiopian highlands by improved understanding of runoff processes. Frontiers in Earth Science. 3:49. DOI:10.3389/feart.2015.00049.

Interpretive Summary: This paper covers recent research to reverse the current upward trend of sediment concentrations in rivers in the Ethiopian highlands although vast amounts of money and labor have been invested in soil and water conservation over the past 50 years. Within the past decade, interdisciplinary research has revealed the hydrological similarity between watersheds, saturated areas of the watershed are source to runoff and sediment; and forests on hillslopes enhances deeper infiltration and facilitates transport to the stream. Consequently, those interventions to remediate high sediment loss should enhance deeper infiltration profile below the restrictive layers, allow drainage of excess rainfall, and combat gully sediment losses at the bottom as well as at the top of the watershed.

Technical Abstract: Despite millions of dollars invested in soil and water conservation practices in the (sub) humid Ethiopian highlands and billions of hours of food-for-work farm labor, sediment concentration in rivers is increasing. This paper reports on the research to reverse the current trend. Based on the understanding of the hydrology of highlands, we provide evidence on sources of surface runoff and sediment and on mechanisms that govern the erosion processes and approaches and how they affect soil and water conservation practices. We suggest that priority in landscape interventions should be given to re-vegetation of the degraded areas so as to reduce the sediment concentration contributions originating from these areas. Additionally, efforts should be directed to gully rehabilitation in the saturated bottom landscape that may consist of vegetating shallow gullies and stabilizing head cuts of deeper gullies Finally, rehabilitation efforts should be directed to increase the rain water infiltration in the upland areas through the hard pan layer by connecting the land surface to the original deep flow paths that exist below about 60 cm. It will reduce the direct runoff during the rainy season and increase baseflow during the dry season.