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Oxford, MS, United States

Tebebu T.Y.,Cornell University | Steenhuis T.S.,Cornell University | Steenhuis T.S.,Bahir Dar University | Dagnew D.C.,Bahir Dar University | And 10 more authors.
Frontiers in Earth Sciences | Year: 2015

Despite millions of dollars invested in soil and water conservation (SWC) 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 SWC 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 hardpan 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. © 2015 Tebebu, Steenhuis, Dagnew, Guzman, Bayabil, Zegeye, Collick, Langan, MacAlister, Langendoen, Yitaferu and Tilahun. Source

Momm H.G.,Watershed Physical Processes Research Unit | Bingner R.L.,Watershed Physical Processes Research Unit | Wells R.R.,Watershed Physical Processes Research Unit | Wilcox D.,Watershed Physical Processes Research Unit
Applied Engineering in Agriculture | Year: 2012

The formation of ephemeral gullies in agricultural fields has been recognized as an important source of sediment contributing to environmental degradation and compromising crop productivity. Methodologies are being developed for assessing gully formation and gully sediment yield. The Annualized Agricultural Non-Point Source (AnnAGNPS) pollution model is an important tool for multi-temporal watershed-scale simulations because it contains the necessary components for ephemeral gully investigation, making AnnAGNPS a commonly used tool for evaluations of agricultural conservation and operation practices. AnnAGNPS requires the user to define the location of ephemeral gullies throughout the watershed, what often constitutes a time consuming task where users may not accurately locate and describe all ephemeral gully locations. Alternatively, herein a GIS-based graphical user interface is described for the automated identification of areas with high probability of forming ephemeral gullies, referred to as potential ephemeral gullies (PEGs), based on the modified Compound Topographic Index (CTI). Through the aid of a study case, PEG mouth locations along with their attributes are generated through an iterative procedure by varying different CTI threshold values (99.9%, 99.5%, 99.0%, 98.5%, and 98%). Three sets of yielded PEG mouth locations and corresponding attributes were then integrated with AnnAGNPS for assessment of the impact of potential ephemeral gullies in the watershed sediment erosion. Analysis of the spatial distribution of estimates of annual average of gully erosion identifies the sub-watersheds prone to ephemeral gully erosion, thus enhancing the applicability of AnnAGNPS to evaluate conservation practices and/or targeted interventions designed to address ephemeral gully erosion at the watershed-scale. © 2012 American Society of Agricultural and Biological Engineers. Source

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