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    EFFECT OF PHYSICAL SOIL AND WATER CONSERVATION MEASURES ON SELECTED SOIL PHYSICOCHEMICAL PROPERTIES IN UBALE MICRO WATERSHED, ARBA MINCH ZURIA WOREDA, SOUTHERN ETHIOPIA
    (Hawassa University, 2019-07-23) ANDARGE ALARO ALTAYE
    Following erosion-induced soil degradation tremendous efforts have been made in implementing different soil and water conservation measures (SWC) in Arba Minch Zuria Wereda. Apart from monitoring and evaluation reports no substantive studies were made and documented on the performances of SWC measures in soil properties so far. The aim of the study is examine the effects of different SWC measures on the selected physicochemical properties of soil among physical SWC measures and position of terrace and, its improvement on soil infiltration rate. Reconnaissance survey was carried out and convenient sampling method was used to select the sampling plot. In cultivated fields treated by level stone bund and level soil bund each with 5 years old age from 15-25% slope category were compared with control. 9 experimental plots were selected. A total of 21 composite soil samples, 18 from treated and 3 from control were collected from the top 15 cm soil depth using “W” sampling design method and analyzed for soil texture, pH [H2O], electrical conductivity (EC), organic carbon (OC), organic matter (OM), total nitrogen (TN), available phosphorous (AP), zinc (Zn), exchangeable potassium (K+ ), exchangeable calcium (Ca2+) and exchangeable magnesium (Mg2+ ) using standard laboratory procedures. 21 undisturbed core samples, 18 from treated and 3 from control plots were collected and analyzed for bulk density (BD), total porosity (TP) and moisture content (MC). Infiltration rate of the soil was measured using a double ring infiltrometer. Results of the experimental study showed that soil MC (%), EC (ds/m), SOC (%), SOM (%), TN (%) and Ca2+ (cmol (+)/kg) were significantly different between SWC measures and the three different position within terrace. % clay were significantly different between SWC measures and interaction effect. Except pH all soil properties were significantly different between SWC measures. Equilibrium infiltration rate was reached on each treatment after (120mins), the LSTB had the highest basic soil infiltration rate, while the control and the LSB received medium and lowest infiltration rate respectively. SOC, SOM and TN were better on the level stone bund and soil bund than the control plot, while the control plots was received the highest pH, EC, Zn, Ca2+ and silt fractions compared with treated plot. The middle position within terraces recorded the higher OC, OM and TN than upper and lower position. Interaction effect of soil and water conservation measures by positions, the level stone bund in the lower position was recorded the higher OC and TN followed by level soil bund on the middle position. The cumulative values of physical SWC measures without proper attention for technical characteristics of the bunds and the maintenance systems improved were decreasing the marginal status of soil nutrients. Biological measures could be integrated for better effect soil fertility. Thus, further research need to be conducted on the effectiveness of bunds in relation to functions relevant for biomass and environmental quality
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    Effects of land use land cover changes on soil erosion risk in Beshilo sub basin and the influence on Tebi dam, north eastern highlands of Ethiopia
    (Hawassa University, 2022-03-15) Andarge Getachew
    Continuous increase of world’s population and demand for food and staple production poses a major challenge for agriculture in the short and medium period. In the current study area, soil loss information and evaluation of risk of potential of soil erosion was not assessed. So, the aim of these study is to assess and analyze the impact of land use land cover change on soil erosion risk using remote sensing and GIS techniques in the upper bushilo sub-basin northern-eastern highland of Ethiopia between 1990 and 2020. Primary materials and tools used are ArcGIS 10.8 software, ENVI 5.3 software, Landsat satellite image of 1990, 2000, 2010, and 2020, ASTER DEM /DEM 30X30 was downloaded from USGS earth explore, Google earth pro as use for base map that also were downloaded for the four study periods. GPS, Camera, Internet access, and computer software were used for data processing and GIS analysis. the watershed’s computed soil loss ranged from zero in plain areas and water courses to large over 68.7t ha-1 yr -1 . In very degraded sloping regions and at specific spots of steep slopes of the watershed, gross soil loss rate ranged to 79.65 t/ha. It shows a larger spatial variation of soil loss over the watershed. It is mainly caused by the difference in soil, rainfall, slope, land cover, and improper land management. The estimated mean annual gross soil loss from 1990-2020 under the entire watershed is about a 9.94 t/ha/yr. Within the study period (1990-2020), 41723.8 ton soil has transported to Tebi dam. The GIS-based RUSLE model can assist decision-makers in effective planning for erosion control studies on risky areas
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    Land Degradation Dynamics Under Land Use Land Cover and Climate Change Projection Towards the Appraisal of Potential Soil and Water Conservation Practices in the Gidabo Watershed, Ethiopian Rift Valley Lakes Basin
    (Hawassa University, 2024-10-11) Rediet Girma Legesse
    The intricate relationship between land use, climate dynamics, and land degradation profoundly impacts the sustainability of ecosystems and human well-being in Ethiopia. This study, conducted in the Gidabo Watershed (GW) within the Ethiopian Rift Valley Lakes Basin (ERVLB), aimed to assess the long-term land use land cover (LULC), evaluate regional climate models (RCMs), assess land degradation indicators, and propose management alternatives. To address these objectives, multidisciplinary approach integrating, remote sensing, geospatial analysis, statistical metrics and hydrological modeling were used. The study identified nine major LULC classes i.e., water body, grass land, forest, agriculture, bare/barren land, built-up, agroforestry, shrub and marsh land. The watershed experienced significant LULC changes between 1985 and 2021, predominantly driven by agricultural expansion at the expense of forest, shrub, and grasslands. Future (2035 and 2050) projections using a hybrid Multi-Layer Perceptron (MLP) and Cellular Automata-Markov chain (CA-MC) model indicated further agricultural expansion, accompanied by declines in forest and grasslands. Furthermore, the study evaluated 11 CORDEX-Africa RCMs and their mean ensemble performance, revealing varied accuracies in reproducing rainfall and temperature patterns over GW from 1991 to 2005. The observed climate trends indicated a significant declining rainfall (-13.38 mm/year) and warming temperatures, with future projections (RCP4.5 and RCP8.5) showing consistent temperature increases. Additionally, the study investigated the impact of LULC and climate change on surface runoff and sediment yield using SWAT model. The results revealed notable increases in surface runoff and sediment yield attributed to LULC changes. Whereas, climate change alone exhibited a diverse influence, with both increases and decreases in surface runoff and sediment yield. Similarly, the combined effects of LULC and climate change demonstrated that certain scenarios led to the increases in surface runoff and sediment yield, while others reduced these processes. This might be attributed to the offset of runoff and sediment reduction by climate change. Soil erosion rates were found to be high, particularly most of the southern and eastern parts of the watershed will generate the highest amount of surface runoff and sediment yield in to the future. Addressing these concerns, soil/stone bund, terracing, contour farming, and reforestation practice can significantly reduce the annual sediment yield in the future. The land degradation neutrality (LDN) assessment from 1985–2003 to 2003–2021 revealed land productivity decline, land cover degradation, SOC loss, and the expansion of land degradation trajectories by 26%. Overall, the findings provide valuable information for stakeholders.