Soil and Water Conservation Engineering

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    EFFECTS OF INTEGRATED USE OF GRASS STRIP COMBINED WITH SOIL BUNDS ON SELECTED SOIL PROPRIETIES: A CASE OF DALTA SUB WATERSHED IN ESSERA DISTRICT, SOUTHWESTERN ETHIOPIA
    (Hawassa University, 2024-10-23) TIZITAW GODARO TOLOLA
    Soil erosion by water constitutes to the most widespread and damaging process of soil degradation. The aim of this study was to determine the effects of integrated use of grass strip combined with soil bunds on selected soil proprieties, to evaluate the Effects of integrated use of soil bund and grass strip combined with soil bunds under different slope gradient and To assess farmer’s adoption on using grass strip combined with soil bunds as soil erosion conservation measures at Dalta sub-watershed. 246-households selected randomly from three kebeles by using systematic random sampling techniques. Three land management practices (Land treated with soil bund alone, soil bund with grass strip and untreated adjacent control plot) were evaluated under three slope of lower slope (3-8%), middle slope (8-15%) and upper slope (15-30%). A total of 27 soil samples were collected from the top 20 cm soil depth with three replication in ‘X’ design square from 10 m x 10 m plots. The results showed that soil Bulk density (Bd), moisture content (MC), soil pH, soil organic matter (SOM), total nitrogen (TN) available phosphorous (Av.p) and cation exchange capacity (CEC) were significantly (p≤0.05) different on land treated by soil bund and soil bund with grass strip as compared to the untreated adjacent control plots. The result also showed, the contents of sand, silt and clay were significantly different with the change in the slope gradient. There were no significant (p≤0.05) differences on soil texture between the conserved and non conserved lands but significant difference with respect to slope gradient. The contribution of soil bund and soil bund with grass strip were effective and promising for land rehabilitation and improving soil properties through minimizing erosion and farmers’ adoption towards the practices at Dalta sub watershed, southwestern Ethiopia. Generally, the difference observed in soil physical and chemical properties between slope positions is not due to grass strip malfunction at slope positions but caused by past erosion events and topographic effects on soil property. Moreover, further research need to be conducted on socio-economic aspects for a better understanding the impact of integrated soil and water conservation interventions.
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    EVALUATING THE EFFECT OF IN SITU RAINWATER HARVESTING TECHNIQUES ON MAIZE PRODUCTION IN MOISTURE STRESS AREAS OF HUMBO WOREDA,WOLAITA ZONE, SNNPRS, ETHIOPIA
    (Hawassa University, 2019-10-28) WUDNESH NABA YAYA
    Rainfall fluctuations, dry spells and drought are the main constraints for rain fed agriculture. In recent years the yield and productivity of maize have been declining drastically. This is mainly attributed due to the lack of appropriate soil and rainfall management practices. This situation is envisaged can be improved under the prevailing conditions by adopting simple water harvesting techniques with the intention of raising and sustaining maize productivity. Accordingly a study was conducted to investigate the effect of some In situ water harvesting techniques on performance of maize crop with respect to soil moisture content, yield and yield components and to assess farmers' perception of water conservation techniques. To achieve the objectives of the study data and information collected through house hold survey and field experiment. The experiment was conducted in Wolaita Zone Humbo Woreda at Abela Sippa kebele, which has an irregular rain fall distribution and a prolonged dry season which leads low soil moisture availability during critical crop growth stages. The study was conducted over a period of one growing season (2010/11) using maize as indicator crop at the farmers training center of the Abela Sippa kebele. The experiment was laid out in a randomized complete block design, with three replications and four treatments. The four treatments used in the study were; Control, Targa , Tie ridge and Zai pits . Findings from this study revealed that maize grain yield and yield components, such as, grain yield, dry matter biomass, and cob length were highly significant (p<0.05) by Targa treatments, but plant height was not significant different. Soil-moisture content over the crop growing season at dry spell periods was significantly higher in Targa and Tie ridges than the control. Targa treatments increased maize yield production to (7.15 ton/ha), Tie ridge increased significantly maize production to (6.19ton/ha), Zai pits yielded (4.5ton/ha) and Control treatment yielded (4.9 ton/ha). Targa and Tie ridge treatments recorded higher net returns (29712, and 25164 ha-1) than Control (20370ha-1) and Zai (14350 ha-1) treatments. The results revealed that the rainwater harvesting technology by the community members to be a good initiative in improving agricultural practices in periods of water scarcity. But, the utilization of the technology is surrounded by various constraints. The major constraints include: labour, cost, lack of knowledge and crops planted on bunds. The findings suggest that Targa structure improved water availability during the growing season, thereby protecting crops from dry periods and it needs minimum cost, less labour power ,and easily constructed by local farmers(not require complicated knowledge)
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    LAND USE LAND COVER CHANGE DYNAMICS AND SOIL LOSS: GIS AND REMOTE SENSING BASED ANALYISIS, IN SHASHOGO WEREDA, HADIYA ZONE, SNNPRS, ETHIOPIA
    (Hawassa University, 2018-10-26) YOSEPH DEBOCH HANKORE
    The relationship between land use land cover change dynamics and soil loss over the last four decades (1973-2015) was investigated using GIS and Remote Sensing data at Shashogo Wereda, Hadiya Zone, SNNPRS, Ethiopia. In order to achieve these, satellite data of Landsat 1 MSS for 1973, Landsat 5 TM for 1986, Landsat 7 ETM plus for 2000, and Landsat 8 OLI for 2015 have been obtained and pre-processed using ERDAS Imagine 2014 software. The Maximum Likelihood Algorithm of Supervised Classification has been used to generate LULC maps. Ancillary data were used to validate the classified LULC maps. For the accuracy of classified LULC maps, a confusion matrix was used to derive overall accuracy and results were above the minimum and acceptable threshold level. For change detection statistics, cross-tabulation matrices method was employed to identify gains and losses between LULC classes. The study analyzed the magnitude of spatial and temporal LULC changes for three consecutive periods; 1973 to 1986, 1986 to 2000, and 2000 to 2015. Moreover, the soil loss from the watershed was estimated using USLE employing GIS tools. Results of the study revealed that the study area has undergone substantial LULC changes. Over the 42yrs, the aerial coverage of cultivated land was increased from 43.9 to 63.0% between 1973 and 2015. Similarly, water body and wetland were increased from 0.6 to 3.9% and 4.4 to 6.7% respectively. Settlement area which was not found in the first and second period of study years, satellite image result have 2.9% proportion in 2015 LULC classification. On the other hand, grass land, bush land, and bare land were decreased from 16.1 to 6.5%, 28.6 to 12.4%, and 6.4 to 4.5% between 1973 and 2015, respectively. Following the land use change pattern, soil loss values were increased in 2015. The estimated soil loss rate in the watershed was 14.31t/ha/yr in 2015. The findings of this study suggested that the rate of LULC change over the study period, particularly intensively cultivated land, bare land, and soil erosion problems need to be given due attention to maintain the stability of the ecosystem
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    EVALUATING SEPARATE IMPACTS OF LAND USE, LAND COVER AND CLIMATE CHANGE ON STREAMFLOW IN UPPER GIDABO WATERSHED, SOUTHERN ETHIOPIA
    (Hawassa University, 2019-12-22) DEGEFU DOGISO BUKURE
    LULC and climate change are two factors that produce major impacts on stream flow and separation of these impacts is important for water resources management as well as policy adaptation and planning for sustainable watershed development. This study was mainly focused on separating the combined and isolated impacts of LULC and climate change on stream flow reduction in upper Gidabo watershed, Southern Ethiopia. The hydrological modeling with the one factor at a time (OFAT) analysis was employed to separate hydrological impacts of LULCC from those of climate change. The SWAT model and MK statistics test were used for the study. SWAT was calibrated and validated in the watershed. The results confirmed that SWAT was a powerful and accurate model for the watershed. The model assessment metrics: NSE, R2 and PBIAS in the data were 0.90, 0.91 and 5% respectively for the calibration period and 0.73, 0.75 and 12.4% respectively for the validation period. After the calibration and validation of the SWAT model, four different scenarios were developed based on one factor at a time (OFAT) experiment. By comparing, the simulated mean annual stream flow components (Qsurf, Qlat and Qbase) results of S1 vs. S2, S3 and S4 for evaluating the effect of LULC and climate change and both on stream flow. The assessment of MK statistics result of climate change showed that precipitation and stream flow exhibited a downward trend and air temperature exhibited upward trends significantly from 1985 to 2016. Evaluation of LULCC from 1985 to 2016 showed that the changes in growth of agricultural land and built-up areas have increased by the annual rate of change 1.81% and 2.33% respectively whereas the mixed forest, evergreen forest and grassland has reduced by the rate of change 1.27%,1.84% and 0.30% respectively. The combined effects of LULC and climate change reduced mean annual lateral flow and base flow values by 7.17mm/yr. and 94.74mm/yr. respectively. The LULCC increased surface runoff by 38.29mm/yr. (56.5%) decreased lateral flow and base flow by 6.23mm/yr. (86.89%) and 26.48mm/yr. (27.95%) respectively while climate change decreased surface runoff, lateral flow and base flow by 29.47mm/yr. (43.5%),0.94mm/yr. (13.11%) and 68.26mm/yr. (72.05%) respectively. Generally, the climate change had the higher impact on base flow reduction while LULCC had higher impact on surface runoff increment and lateral flow reduction in the study watershed. Therefore, to mitigate the negative impacts of climate change combined with LULC change, local and national policymakers are encouraged to apply science-based watershed and land use planning and implement appropriate management approaches in the upper Gidabo watershed
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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
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    HYDRO-SEDIMENT RESPONSES TO MANAGEMENT OPTIONS UNDER CURRENT AND FUTURE CLIMATE CHANGE SCENARIOS IN MAYBAR SUB WATERSHED, SOUTH WOLLO ZONE, ETHIOPIA
    (Hawassa University, 2022-10-22) MULUKEN LEBAY EGIGU
    Climate change coupled with inappropriate land use management is a serious environmental challenge in the highland part of Ethiopia. The aim of this study was to investigate hydro-sediment responses to management options under current and future climate change scenarios in Maybar watershed, Northern Ethiopia. We employed soil and water assessment tool (SWAT) for hydrologic modeling and CORDEX-climate data under RCP 4.5 and RCP 8.5 emission scenarios was used for climate projections. Soil map was prepared by digitizing soil characterization map of the watershed generated by Weigel in 1986. DEM data with 2m spatial resolution was obtained from water and land resource center and land use classification was done through digitization of google earth images. Better agreement between calibrated SWAT simulation and observed variables was achieved. Delta change bias correction method was empolyed to improve the climate simulation in reproducing the observed climate variables. We found a considerable increase in annual precipitation by 18.71% and 22.33% for RCP 4.5 and RCP 8.5, respectively compared with the current climate conditions. Climate change induced hydro-sediment results were observed to be consistent with predicted precipitation. Under the current climatatic conditions, average sediment yield at the subbasin scale varies from negligible (under terrace complementation) to approximately more than 50 t ha-1 yr-1 with a basin average of 32 t ha-1 yr-1 (under no-terrace conditions). The implementation of management alternatives gets the dry seasons hydrological behavior of the catchment improved and climate change induced sediment yield reduction. Generally, the information could possibly support decision makers and planners to implement best-fitted management options and thereby reduce current and expected aggressive sediment loss situations.