Soil and Water Conservation Engineering

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Start date: 2020End date: 2024

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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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    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.