ASTU ETD

Adama Science and Technology University Library Electronic Theses & Dissertations (ASTU- ETD) is a new digital institutional repository system that collects, preserve and distribute the scholarly output of the university, mainly postgraduate Electronic Thesis and Dissertation (ETD), articles, proceedings. The system is dedicated to help users to find all the information they might require in order to format and successfully submit their graduate thesis, dissertation and publications electronically. The user friendly web interface enables to maximize & optimize the resource sharing among ASTU different Colleges.

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Synthesis of Cobalt Doped ZnO/Co₃O₄ heterostructures for Efficient methylene blue dye degradation applicationThesis
(ASTU, 2025) Degefa Bekele
Catalysis research has turned its attention to improving optical and charge transfer materials by combining doping and interfacial engineering. Cobalt-doped ZnO/CoO (CZnO) heterostructures were created in order to accomplish an effective photocatalytic process for the breakdown of methylene blue dye. Successful cobalt incorporation and heterojunction development were confirmed by XRD analysis, which showed changes in diffraction peaks and the appearance of distinctive Co3O4 peaks.The crystallite sizes for pure ZnO and the doped heterostructure were detected as 26.3 nm and 10.7 nm, in the order given. High resolution TEM images showed sharp lattice patterns with d-spacings of 0.273 nm for ZnO and 0.241 nm for Co₃O₄, further verifying the interface formation. CZnO particles exhibited nanoscale dimensions ranging from 27 to 50 nm. Surface morphology analysis via FESEM and elemental mapping through EDX confirmed a uniform distribution of cobalt and the absence of impurities. UV-vis DRS technique indicated improved light absorption and a notable reduction in band gap energy upon cobalt doping, with indirect bandgaps of 3.05 eV for ZnO and 1.71 eV for CZnO. Photoluminescence (PL) spectra showed decreased emission intensity for CZnO, suggesting efficient charge separation at the heterojunction interface. The photocatalytic performance of CZnO showed a 4.5-fold increase in the degradation rate of methylene blue (k = 0.141 min⁻¹) compared to pure ZnO (k = 0.031 min⁻¹), attributed to enhanced optical and charge transport properties. The results confirm the potential of the porous CZnO heterostructure, prepared via a straightforward combustion method, for scalable photocatalytic applications.
Evaluating Impacts Of Climate Change On Water Availability: The Case Of Hargeisa Watershed In SomalilandThesis
(ASTU, 2025) Ibrahim Ahmed
The Hargeisa watershed is the lifeline water basin located in the Marodi-jeh region of Somaliland, which includes the capital city of Hargeisa. However, as a semi-arid and groundwater-dependent system, the watershed is highly vulnerable to the impacts of climate change. This study quantifies these impacts using the Soil and Water Assessment Tool plus (SWAT+) model, driven by downscaled data from three coupled model inter comparison project phase six (CMIP6) of Global Circulation Models (CanESM5, NorESM2-MM, GFDL-ESM4) under SSP2-4.5 and SSP5-8.5 scenarios. A regionalization approach using data from the gauged Dagahbur catchment was employed to overcome local data scarcity. Historical analysis (1995-2024) exposed a significant increasing trend in annual precipitation (up to 13.19 mm/year) alongside regional warming. Future projections indicate a complex hydrological response to accelerating warming, which could exceed +6.8°C by the end of the century under SSP5-8.5. Evapotranspiration is projected to increase substantially across all scenarios (+46.0% to +184.2%). Critically, despite this, groundwater recharge shows a consistent and significant increase, ranging from +4.1% to as high as +781.0%. Completely different, projections for surface runoff are highly uncertain, ranging from a decrease of -32.7% to an increase of +135.8%. This study concludes that while the Hargeisa watershed may see improved groundwater security, it faces a dual risk of increased droughts and heightened flood potential. These findings provide a quantitative basis for developing adaptive water management strategies to ensure the region's long-term water security.
Evaluation Of Irrigation And Drainage Performance: The Case Of Amibara Irrigation SchemeThesis
(2026) Geremew Ajema
Irrigation and drainage systems play a critical role in sustaining agricultural productivity in semi arid regions; however, the Amibara Irrigation Scheme has increasingly suffered from water scarcity, poor water distribution, deteriorating drainage, and rising soil salinity, threatening crop production and land sustainability. The objective of this study was to evaluate the performance of the irrigation and drainage systems, as well as irrigation water use efficiency, within the Amibara Irrigation Scheme. A mixed-methods research design was employed, combining quantitative field measurements with qualitative assessments to obtain comprehensive system-level and field-level performance insights. Primary data included canal discharge measurements, soil moisture readings, groundwater levels, soil and water samples, and field observations, while secondary data were obtained from the CLIMWAT database. CROPWAT 8.0 was used for estimating crop water requirements and comparing theoretical and actual irrigation demands. The results showed significant performance limitations at both irrigation and drainage levels. Overall irrigation efficiency was 42%, with conveyance efficiencies of 62–71% and application efficiency of 58%, indicating substantial seepage losses, deep percolation, and non-uniform field application. Storage efficiency was 71%, while distribution uniformity remained below recommended thresholds. Drainage performance was poor, particularly in Middle and Lower command areas, where water tables as shallow as 0.55–0.65 m and soil salinity levels of 3.7–4.1 dS/m were recorded values approaching or exceeding crop tolerance limits. In conclusion, the study found that the Amibara Irrigation Scheme is operating far below expected performance standards due to combined infrastructural, hydrological, and institutional challenges that reduce water productivity and accelerate land degradation. The study recommends (i) rehabilitating and lining canals to minimize losses, (ii) completing drainage upgrading works, including Phase II of the Amibara Drainage Project, and (iii) improving irrigation scheduling and on-farm water management.
Flood Inundation Mapping In Webishabele River Using Google Earth Engine And Hec-Ras Model: Case Study Of Beletwayne City, SomaliaThesis
(ASTU, 2025) Abdirahman Yousuf
Flooding from the Shebelle River is a persistent and severe hazard in Beletweyne City, Somalia, causing significant loss of life and infrastructure damage. This study modeled these dynamics by integrating the HEC-RAS hydraulic model with the Google Earth Engine (GEE) geospatial platform. A 1D/2D HEC-RAS model was developed using a 30m Digital Elevation Model (DEM) and Manning’s roughness coefficients derived from land use and land cover (LULC) data. The 2D model was calibrated against the October 2019 flood event, yielding a coefficient of determination R2=0.89. Spatial validation against Sentinel-1 satellite imagery via GEE showed 54.106% overlap with the observed flood extent. Simulation results for 25, 50, and 100-year return periods reveal escalating risk to the urban area: the 25-year event produced a maximum flood depth of 3.80 m and an inundated area of 4.87 km², while the 50-year event produced a maximum depth of 5.97 m and an inundated area of 8.56 km². The 100-year event reached a depth of 8.58 m and an inundated area of 11.65 km², aligning closely with the 8.30 m bank-full level observed during the 2019 extreme floods. Unsteady flow simulations further generated critical risk maps for flood velocity, arrival time, and inundation duration. These high-resolution outputs provide a scientifically validated framework essential for risk-based zoning and the development of early warning systems in Beletweyne.
Comparison of Geostudio and Plaxis in the Embankment dam Seepage and Slope Stability analysis: A case Study of Kundhi Dam, Oromia EthiopiaDissertation
(2025) Haimanot Shume
This study presents a comparative evaluation of seepage and slope stability analysis of the Finna Kundhi earthen dam located in Oromia Region, Ethiopia, recognizing that seepage and slope failure are major causes of embankment dam instability. The main objective of the study was to compare the performance of GeoStudio and PLAXIS software in simulating seepage behavior and slope stability under critical loading conditions. Two-dimensional numerical modeling was carried out using GeoStudio (SEEP/W and SLOPE/W) and PLAXIS based on finite element and limit equilibrium methods. Seepage and stability analyses were conducted under steadystate seepage at full supply level, end-of-construction, steady-state, and rapid drawdown conditions using available geotechnical and hydraulic data of the dam. The results showed that both software tools produced comparable seepage patterns, pore water pressure distributions, and factors of safety, with minor differences attributed to their numerical approaches. All computed factors of safety satisfied recommended international standards, indicating that the dam is stable under the considered conditions. The study recommends the use of GeoStudio for routine dam safety evaluation and PLAXIS for advanced stress–deformation analysis, together with continuous seepage monitoring to enhance long-term dam safety.