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Application of models to identify soil erosion processes, estimate sediment accumulations into lakes, technically design best management practices, and monitor and evaluate different management scenarios in the Ethiopian highlands has been growing. However, proper model implementation will require verification of the model against known output parameters. This study investigated the performance and applicability of one such model, Soil and Water Assessment Tool (SWAT). Sequential Uncertainty Fitting-2 (SUFI-2), a SWAT-CUP2012 sub-module computer program, was applied to optimize the parameters of the SWAT using monthly observed sediment yield data at a monitoring site in Maybar experimental watershed, Ethiopia. Thirteen hydrological years were used for model calibration, validation and uncertainty analysis. Multi-objective function statistics: P-factor (23%, 12%), R-factor (0.63, 0.40), Nash–Sutcliffe efficiency, NSE (0.55, 0.53), root mean square error-observations standard deviation ratio (RSR) (0.67, 0.69), coefficient of determination, R 2 (0.55, 0.52), and percent bias, PBIAS (− 14.6%, 0.8%) for calibration and validation, respectively were obtained. The model evaluation statistics suggested that SWAT extremely under-predicted peak sediment loads in both calibration and validation periods. However, according to model evaluation guidelines and performance ratings, modeled sediment yield can be rated as satisfactory. Although the accuracy of modeling of soil erosion processes using SWAT is likely affected by spatial variation of watershed characteristics, and scale of management, among other factors, Maybar calibrated SWAT model do suggest a broad guide: prediction of sediment yield at ungauged watershed with SWAT could be possible under comparable topography, land use, soil, management and climate condition for the purpose of soil erosion assessment, scenario analysis, and recommendation of best management practices to support watershed management initiatives in the Ethiopian highlands. [ABSTRACT FROM AUTHOR]

Land use/land cover changes in a lake drainage basin reflect changes in the magnitude of the water balance components and rate of sediment deposition in a lake as a reflection of the fundamental linkage between what happens in a lake considered against what is happening in the drainage basin of the lake. The objective of this study was to quantify the spatio-temporal land cover/land use changes across the Lake Hayq closed drainage basin in north-east Ethiopia over a 50-years period, using multitemporal remote sensing and geospatial data. Two historical occasions of aerial photographs (1957 and 1986) and one satellite image (2007) were examined with image analysis tools: Leica Photogrammetric Suite ( LPS 9.2) Project Manager, ArcGIS10.0, and ERDAS EMAGINE 9.2. Seven aerial coverage of land use/land cover categories were identified and mapped for the past three historical times. The results indicated that farmlands/settlements and shrublands/degraded lands increased by 43.1% and 136.9%, at an annual rate of 27.4 and 13.5 ha year−1, respectively, between 1957 and 2007. In contrast, bushlands, grasslands, forestlands and lake surface area were diminished by 68.8%, 62.7%, 90.5% and 7.6%, at a rate of 24.0, 7.6, 6.1 and 3.7 ha year−1, respectively, over the past five decades. The basin had undergone significant transformation in land use/land cover over the past half century, affecting the lake's biophysical stability by accelerating soil erosion in the basin, sediment accumulation, and a reduced quantity and quality of cumulative stream flow into the lake. [ABSTRACT FROM AUTHOR]

This study aimed to determine the spatial variation of topsoil properties as influenced by slope aspects and vegetation types. Three vegetation types and two slope aspects were considered. Disturbed and undisturbed samples were taken from the top soils. A two-way analysis of variance was used to test significant mean differences (α = 0.05). Results showed that contents of bulk density, total porosity, organic matter and exchangeable magnesium were significantly different with changes in slope aspect ( P < 0.05). Textural classes, organic matter, available phosphorus, carbon-to-nitrogen ratio, cation-exchange capacity, per cent base saturation and exchangeable bases demonstrated significant variation among vegetation types ( P < 0.05). The south-facing aspect and the grass vegetation showed higher bulk density but lower organic matter and total porosity. As a remedy for the identified problems, there is a need to undertake plantation of indigenous trees. [ABSTRACT FROM AUTHOR]