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Mehammednur Seid N.,P.A. College | Yitaferu B.,Amhara Regional Agricultural Research Institute ARARI | Kibret K.,Haramaya University | Ziadat F.,International Center for Agricultural Research in the Dry Areas
Applied and Environmental Soil Science

Information about the spatial distribution of soil properties is necessary for natural resources modeling; however, the cost of soil surveys limits the development of high-resolution soil maps. The objective of this study was to provide an approach for predicting soil attributes. Topographic attributes and the normalized difference vegetation index (NDVI) were used to provide information about the spatial distribution of soil properties using clustering and statistical techniques for the 56 km2 Gumara-Maksegnit watershed in Ethiopia. Multiple linear regression models implemented within classified subwatersheds explained 6-85% of the variations in soil depth, texture, organic matter, bulk density, pH, total nitrogen, available phosphorous, and stone content. The prediction model was favorably comparable with the interpolation using the inverse distance weighted algorithm. The use of satellite images improved the prediction. The soil depth prediction accuracy dropped gradually from 98% when 180 field observations were used to 65% using only 25 field observations. Soil attributes were predicted with acceptable accuracy even with a low density of observations (1-2 observations/2 km2). This is because the model utilizes topographic and satellite data to support the statistical prediction of soil properties between two observations. Hence, the use of DEM and remote sensing with minimum field data provides an alternative source of spatially continuous soil attributes. © 2013 Nurhussen Mehammednur Seid et al. Source

Guzman C.D.,Cornell University | Tilahun S.A.,Bahir Dar University | Zegeye A.D.,Cornell University | Zegeye A.D.,Amhara Regional Agricultural Research Institute ARARI | And 2 more authors.
Hydrology and Earth System Sciences

Loss of top soil and subsequent filling up of reservoirs in much of the lands with variable relief in developing countries degrades environmental resources necessary for subsistence. In the Ethiopia highlands, sediment mobilization from rain-fed agricultural fields is one of the leading factors causing land degradation. Sediment rating curves, produced from long-term sediment concentration and discharge data, attempt to predict suspended sediment concentration variations, which exhibit a distinct shift with the progression of the rainy season. In this paper, we calculate sediment rating curves and examine this shift in concentration for three watersheds in which rain-fed agriculture is practiced to differing extents. High sediment concentrations with low flows are found at the beginning of the rainy season of the semi-monsoonal climate, while high flows and low sediment concentrations occur at the end of the rainy season. Results show that a reasonably unique set of rating curves were obtained by separating biweekly data into early, mid, and late rainfall periods and by making adjustments for the ratio of plowed cropland. The shift from high to low concentrations suggests that diminishing sediment supply and dilution from greater base flow during the end of the rainfall period play important roles in characterizing changing sediment concentrations during the rainy season. © 2013 Author(s). Source

Amare T.,Amhara Regional Agricultural Research Institute ARARI | Amare T.,University of Bern | Zegeye A.D.,Amhara Regional Agricultural Research Institute ARARI | Zegeye A.D.,Cornell University | And 4 more authors.
Ecohydrology and Hydrobiology

Excessive runoff and soil erosion in the upper Blue Nile Basin poses a threat that has attracted the attention of the Ethiopian government because of the serious on-site effects in addition to downstream effects, such as the siltation of water harvesting structures and reservoirs. The objective of the study was to evaluate and recommend effective biophysical soil and water conservation measure(s) in the Debre Mewi watershed, about 30 km south of the Lake Tana. Six conservation measures were evaluated for their effects on runoff, soil loss, and forage yield using runoff plots. There was a significant difference between treatments for both runoff and soil loss. The four-year average annual soil loss in the different plots ranged from 26 to 71 t ha -1, and total runoff ranged from 180 to 302 mm, while annual rainfall varied between 854 mm in 2008 and 1247 mm in 2011. Soil bund combined with elephant grass had the lowest runoff and soil loss as compared to the other treatments, whereas the untreated control plot had the highest for both parameters. As an additional benefit, 2.8 and 0.7 t ha-1 year -1 of dried forage was obtained from elephant and local grasses, respectively. Furthermore, it was found that soil bund combined with Tephrosia increased soil organic matter by 13% compared to the control plot. Soil bund efficiency was significantly enhanced by combining them with biological measures and improved farmers' perception of soil and water conservation measures. © 2014 European Regional Centre for Ecohydrology of Polish Academy of Sciences. Source

Tebebu T.Y.,Cornell University | Tebebu T.Y.,Bahir Dar University | Abiy A.Z.,Bahir Dar University | Zegeye A.D.,Bahir Dar University | And 12 more authors.
Hydrology and Earth System Sciences

Gully formation in the Ethiopian Highlands has been identified as a major source of sediment in water bodies, and results in sever land degradation. Loss of soil from gully erosion reduces agricultural productivity and grazing land availability, and is one of the major causes of reservoir siltation in the Nile Basin. This study was conducted in the 523 ha Debre-Mawi watershed south of Bahir Dar, Ethiopia, where gullies are actively forming in the landscape. Historic gully development in a section of the Debre-Mawi watershed was estimated with semi structured farmer interviews, remotely sensed imagery, and measurements of current gully volumes. Gully formation was assessed by instrumenting the gully and surrounding area to measure water table levels and soil physical properties. Gully formation began in the late 1980's following the removal of indigenous vegetation, leading to an increase in surface and subsurface runoff from the hillsides. A comparison of the gully area, estimated from a 0.58 m resolution QuickBird image, with the current gully area mapped with a GPS, indicated that the total eroded area of the gully increased from 0.65 ha in 2005 to 1.0 ha in 2007 and 1.43 ha in 2008. The gully erosion rate, calculated from cross-sectional transect measurements, between 2007 and 2008 was 530 t ha -1 yr -1 in the 17.4 ha area contributing to the gully, equivalent to over 4 cm soil loss over the contributing area. As a comparison, we also measured rill and interrill erosion rates in a nearby section of the watershed, gully erosion rates were approximately 20 times the measured rill and interrill rates. Depths to the water table measured with piezometers showed that in the actively eroding sections of the gully the water table was above the gully bottom and, in stable gully sections the water table was below the gully bottom during the rainy season. The elevated water table appears to facilitate the slumping of gully walls, which causes the gully to widen and to migrate up the hillside. © Author(s) 2008. Source

Tewabe D.,Amhara Regional Agricultural Research Institute ARARI | Getahun A.,Addis Ababa Institute of Technology | Dejen E.,Amhara Regional Agricultural Research Institute ARARI
Ecohydrology and Hydrobiology

We sampled fishes of the rivers Gendwuha, Guang, Shinfa, and Ayima with 6, 8, 10, 12 and 14 cm stretched mesh gillnet, monoflament of different mesh sizes, hook and line, fykenet and castnet. During October 2007 through January 2008 in both dry and wet seasons. 27 fsh species were identified from the four rivers represented by the families: Centropomidae, Cichlidae, Bagridae, Schilbeidae, Clariidae, Mochokidae, Malapteruridae, Osteoglossidae, Mormyridae, Characidae, Citharinidae and Cyprini-dae. Species richness was slightly highest in the rivers Shinfa and Ayima - 20 species each, whereas 16 and 18 species were identified from Gendwuha and Guang rivers, respectively. Most destructive fishing methods used in the region include plant poisons and chemicals (Malathion) which are nonselective and dangerous for all biota. Action towards awareness creation in this respect should be urgently undertaken before extinction of species. Source

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