http://ir.bdu.edu.et/handle/123456789/11548 2001-01-13T05:51:12Z http://ir.bdu.edu.et/handle/123456789/12964 IDENTIFICATION OF EROSION HOT-SPOT AREAS FOR PRIORITIZATION OF CONSERVATION MEASURES USING THE SWAT MODEL IN RIBB WATERSHED, ABBAY BASIN, ETHIOPIA BETELHEM FETENE Identifying erosion hot-spot areas of a watershed/basin and isolating best management practices (BMPs) for erosion-prone sub-watersheds is imperative for effective soil loss reduction and lessening its on-site and off-site effects. The present study aimed to identify erosion hot-spot areas for prioritization of conservation measures and evaluate BMPs for reducing soil erosion using the Soil and Water Assessment Tool (SWAT) model in Ribb watershed, Ethiopia. The SWAT model was calibrated (1995-2002) and validated (2003-2008) using flow and sediment data in the SWAT Calibration and Uncertainty Program (SWAT-CUP). The study evaluated the effectiveness of three BMPs against the baseline conditions for reducing soil erosion, such as filter strips Scenario (Scenario F), stone/soil bunds Scenario (Scenario S) and reforestation Scenario (Scenario R). The result indicated that about 95% of the watershed are identified as erosion hot-spot areas, which experienced sediment yield > 11 t ha−1 yr−1. The mean annual sediment yield (1995-2008) of the watershed at the baseline conditions was nearly 29 t ha−1 yr−1. The implementation of Scenario F, Scenario S and Scenario R reduced the baseline sediment yield by 31%, 76% and 62% at the watershed scale, respectively. At the sub-watershed levels, Scenario S and Scenario R reduced the mean annual sediment yield from 45-90% and 0-90%, respectively. Therefore, the study suggests implementations of Scenario S and Scenario R for effective soil erosion reduction in the study watershed in particular and to other watersheds in Ethiopia in general which have similar environmental settings. 2022-01-24T00:00:00Z http://ir.bdu.edu.et/handle/123456789/12963 Modeling the Impacts of Land Use/Land Cover Changes on the Hydrological Processes of Upper Gilgel Abay Watershed, Abbay River Basin, Ethiopia Wassie Abuhay Land use land cover (LULC) changes is among the major environmental challenges in the globe. This study aimed to evaluate the impacts of land use/land cover (LULC) changes on the hydrological processes of the Upper Gilgel Abay watershed, Upper Blue Nile Basin. The study used three times series Landsat images, namely Landsat 5 TM 1986, Landsat ETM+ 2003 and Landsat 8 OLI-TIRS 2021. The supervised image classification technique for classifying the Landsat images into LULC classes and the Soil and Water Assessment Tool (SWAT) model for analyzing the hydrological processes were used. The result has shown that an expansion of cultivated land and a reduction of forest, shrubland, grassland and water body were observed during 1986-2003 periods. On the other hand, between 2003 and 2021 periods, cultivated land, grassland and water body were reduced while forest and shrubland were increased. Consequently, surface runoff and water yield were increased during 1986-2003 periods while these hydrological components were reduced in 2003-2021 periods. In contrast, lateral flow, groundwater flow, soil water and evapotranspiration were reduced during 1986-2003 periods and increased during 2003-2021 periods. The findings of this study mainly revealed that the expansion cultivated land on the expense of other land use conversion led to deterioration of the hydrological processes in the study watershed. The result suggests improvements of vegetation cover to reduce surface runoff and increase groundwater in the study watershed in particular and in the Ethiopian Highlands in general. 2022-01-24T00:00:00Z http://ir.bdu.edu.et/handle/123456789/12962 Changes in Historical Rainfall and Temperature Extremes in the Upper Blue Nile Basin of Ethiopia Jemal Ali Ethiopia is a resourceful and densely populated country often hit by drought and flood disasters that cause great damage to life and property every year. The frequency and intensity of extreme events have increased significantly in recent decades due to climate change and global warming. This study aimed to analyze the historical changes in rainfall and temperature extremes in the Upper Blue Nile Basin of Ethiopia during the periods from 1980 to 2019. The Mann-Kendall nonparametric trend test and the Theil-Sen’s slope estimator were used to estimate annual and seasonal trends. The rainfall and temperature extremes were analyzed with the RClimDex software by selecting ten rainfall and eleven temperature indices. The results showed a positive trend in annual, Belg (March-May) and Bega (October-February) rainfall in more than 54% of the stations and a decreasing trend in Kiremt (June-September) rainfall in 65.4% of the stations. Several extreme rainfall indices showed insignificant positive trends in the basin. Although there is a positive trend in extreme rainfall, the number of consecutive wet days (CWD) and the simple daily intensity index (SDII) show insignificant negative trends in most stations. In addition, a warming trend of the annual and seasonal maximum and minimum temperature and extreme temperature indices were noted. Overall, the increase in extreme rainfall and a warming trend in the extreme temperature indices indicate signs of climate change in the Upper Blue Nile Basin. These results, therefore, highlight the need to plan and implement effective strategies for adapting and mitigating climate change. 2022-01-24T00:00:00Z http://ir.bdu.edu.et/handle/123456789/12961 Estimating Soil Erosion Responses to Land Use/ Land Cover Changes using RUSLE Model in Angereb Watershed, Lake Tana Basin, Ethiopia Lemlem Sema Understanding the impact of land use/land cover (LULC) change on soil erosion and sedimentation is highly important for land resource management. This study was intended to investigate the impact of LULC changes on soil erosion and sediment yield in the Angereb watershed. The supervised land use classification technique was used to classify Landsat 4-5 Thematic Mapper of 1991, 2001, 2011, and Landsat 8 Operational Landsat Imagery of 2021. The GIS-based Revised Universal Soil Loss Equation (RUSLE) model was employed to estimate the rate of soil erosion. As the LULC classification result of the four years indicated that cultivated land increased from 29.6 to 42.6% between 1991 and 2021. On the other hand, bush and shrub land had decreased from 46.2 to 32.4% between 1991 and 2021. Forestland also shrinks from 16.7 to 8.8% in the same period. Such type of LULC changes increased the mean annual soil erosion rate from 39.6 in 1991 to 43.2, 53.6, and 62 t ha-1yr-1 in 2001, 2011, and 2021 respectively. Similarly, sediment yield increased from 3.6 t ha-1yr-1 in 1991 to 4.5 t ha-1yr-1 in 2001 and 4.9 t ha-1yr-1 in 2011 to 5 t ha-1yr-1 in 2021. Especially, the upstream mountainous and steeper parts of the study watershed were the erosion hotspot areas in the watershed. The increase in soil erosion from the four periods was a direct reflection of the change of bush and shrublands, forestlands, and grasslands to cultivated land. As a short-term plan, the watershed areas that have a high erosion rate should be prioritized during Soil and Water Conservation (SWC) practices. To minimize soil erosion sustainably for the future, land use plans are advised to be implemented to conserve hill slopes from cultivation. 2022-01-24T00:00:00Z