Soil and Water Conservation Engineering

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/67

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Start date: 2017Subject: search.filters.subject.Soil erosion

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    ESTIMATION OF SEDIMENT YIELD AND EFFECTIVENESS OF LEVEL STONE BUNDS TO REDUCE SEDIMENT LOSS: IN GUMARA-MAKSEGNIT WATERSHED, NILE BASIN, ETHIOPIA
    (Hawassa University, 2018-10-21) ATIKILT ABERA ALEMAYEHU
    The study was conducted in Gumara-Maksegnit watershed and it’s sub-catchments to estimate event-based sediment yield and to evaluate the effectiveness of level stone bunds based on sediment loss reduction. Modified Universal Soil Loss Equation (MUSLE) was used for estimation of sediment yield. The model input parameters were collected from different sources and these are discretized and preprocessed with the help of various suitable software and tools. Finally, all six model factors were combined together using the raster calculator in map algebra to estimate the sediment yields of the study watersheds. The event-based mean observed and model estimated sediment yields were (0.5581, 0.4031 ton ha-1 ) for Gumara-Maksegnit watershed, (0.5125, 0.4194 ton ha-1 ) for treated sub-catchment and (1.0694, 1.0150 ton ha-1 ) for untreated sub-catchments respectively. The sediment losses between treated and untreated sub-catchments were highly significantly different when the sediment loss reduced by 58.8% as a result of level stone bund interventions. However, the observed and estimated sediment losses are not significantly different within a watershed. Hence, the model was well performed to estimate sediment yield in the study area with R2 (0.62, 0.72 and 0.7) and NSE (0.53, 0.71 and 0.34) for treated, untreated and Gumara-Maksegnit watershed respectively. Hence, the result showed that the Modified Universal Soil Loss Equation (MUSLE) model was well suited for reliable applications of sediment yield estimation in the study area as well as similar agroecologies
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    IMPACT OF SOIL EROSION ON CHELELEKA WETLAND AREA OF TIKURWUHA CATCHMENT, LAKE HAWASSA WATERSHED, SOUTHERN ETHIOPIA
    (Hawassa University, 2017-10-22) ASHAGO AGARO ALIT
    Environmental depletion and loss of wetland ecosystem due to soil erosion from the nearby catchment is an alarming issue because of its adverse impact on the environment that aggravated due to human pressure. This research was carried out on Tikurwuha catchment that has faced tremendous environmental problems in the last 30 years. The objective of the research was to assess the current status of soil erosion from the catchment and to detect changes on each land use /land land cover in the catchment in 1985, 2000 and 2015 time periods. The study related to estimating soil erosion from the catchment was undertaken using Revised Universal Soil Loss Equation (RUSLE) model integrating with Geographic Information System (GIS). Change in the area detected using 1985, 2000 and 2015 year satellite images. Questionnaires and focused group discussion were employed to identify major contributed factors for soil erosion in the catchment within 30 years. The result indicated that the annual soil loss in the catchment within slope classification, ranges from 0.003 to 19,886.5 t//yr and the average soil loss ranges 0.004 t/ha/yr to 13.61 t/ha/y and about 60.8% of the study area were identified to experience very low annual soil loss, whereas 21.16% of the study area experienced low annual soil losses and 18 % of the study area experienced as its high contribution for annual soil loss in the catchment. Significant change has occurred and observed in the wetland sub- catchment by analyzing three years Land sat images in the last 30 years. The areas that were covered with marsh land in 1985 were 3609.92 ha this was changed to 2441.40ha in the 2000 and this was decreased to 1651.74 ha in the 2015 and has shown 54.22% decrease from 1985 to 2015. The area that were covered with forest in 1985 was 2950.78ha and this was changed to 4409.01ha in 2000 and this was decreased to 1261.97ha in 2015 and has shown 57.14% decrease from 1985 to 2015. The area that were covered with cultivated land in 1985 was 20932ha and this increased to 31912.55 ha in 2000 and this has increased to 33080.75 ha in 2015 and it has shown 58.02% increase from 1985 to 2015. Farmers’ attitudes were also analyzed and they replied that forest degradation, agricultural land expansion and unwise use of catchments are the main causes for the decrease of wetland areas and for the soil loss in the catchmen