Hydraulic Engineering

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    GROUNDWATER POTENTIAL MAPPING USING SWAT MODEL AND GIS BASED MULTI-CRITERIA DECISION ANALYSIS: A CASE STUDY IN GIDABO WATERSHED, RIFT VALLEY LAKES BASIN, ETHIOPIA
    (Hawassa University, 2022-07-08) BIRUK TAMIRU TADELE
    Groundwater is the water that is located in the subsurface and saturates the rocks and soil beneath the ground surface. Groundwater is the most valuable natural resources for mankind for drinking, industrialization and irrigation in present day, but the availability is reduced gradually due to over exploitation and lack of management. However, identifying the groundwater potential zones in certain areas of Ethiopia is still challenging in terms of time and cost for resolving water scarcity problems and the management system of groundwater. A systematic assessment and identification of groundwater is essential for proper utilization and management of this precious natural resource. In recent years, Geographic information system based studies have gained much prominence in groundwater exploration, because it is rapid and will provide first-hand information on the resource for further developments. Therefore, the present study was conducted with an objective to identify the groundwater potential of Gidabo catchment, Rift Valley Lakes Basin of Ethiopia using SWAT and GIS-based MCDA techniques. Thematic maps were developed, for ten major parameters (recharge, soil, lineament density, lithology, land-us/ land-cover, geomorphology, slope, drainage density, Roughness and Topographic wetness index (TWI)) that affect the occurrence and movements of groundwater. Recharge was simulated by using SWAT model, the rest thematic layers were developed using ArcGIS 10.4 and Weights assigned to each thematic maps were based on their characteristics and water potential capacity through analytic hierarchy approach (AHP). The thematic layers were subjected to weight sum overlay in ArcGIS spatial analysis tool box, to delineate groundwater potential zone map. The resulted groundwater potential zone was categories in to four classes, namely high, moderate, low and very low. Generally Low and very low groundwater potential zones were found around highland area which coincide with structural hills, peak of the mountain and hard geological formation. The accuracy of the output was cross-validated with information on groundwater prospects of the catchment. Finally, it can be concluded that SWAT and GIS-based MCDA-AHP techniques is very effective and useful for the delineation and identification of groundwater potential zones in the study area.
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    GROUNDWATER POTENTIAL MAPPING USING GIS AND REMOTE SENSING: A CASE STUDY IN WELMEL WATERSHEDE, GENALE-DAWA RIVER BASIN, SOUTHEAST ETHIOPIA
    (Hawassa University, 2023-08-03) HAILEYESUS HIFAMO HILLO
    To fulfil the demand of a rapidly growing population in drought-prone areas with high rate of urbanization, identification and management of groundwater resources are required. In the welmel catchment, a search for an alternative source of water has been always a major issue. The current practice of groundwater potential zone (GWPZ) identification is time consuming and uneconomical. This study applied integration of GIS-Remote Sensing (RS) and Analytical Hierarchy Process (AHP) for mapping the GWPZ of welmel catchment , Southeast Ethiopia. This technique is a fast, accurate, and feasible technique. Groundwater potential zone influencing parameters were derived from Operational Land Imager 8, digital elevation model(DEM) 20*20 resolution and secondary sources were utilized in this research. These were geomorphology, lineament density , lithology, rainfall, drainage density , slope , elevation , LULC, and soil texture were prepared . Borehole data were used for results validation. All thematic layers were reclassified based knowledge based analysis that was reviewed from different kinds of literature. Then the weight for each factor was assigned according to their relative importance as per suitable based on Saatty's scale of AHP. The important factors result show that geomorphology and lineament density have a higher weight and soil texture has the lowest weight for identifying groundwater potential zone . For weights allocated to each parameter, the consistency ratio obtained was 0.061, which is less than 0.1, showing the weight allocated to each parameter is acceptable. The resulting GWPZ of the study area indicates four zones representing Very Low, Low, Moderate and High . The areal extent of high and moderate GWPZ is 350 km2 and 2256 km2 , respectively. low and very low GWPZ covers 10356 km2 and 1547km2 areas. The particular direction of groundwater flow is towards the NE and SE, coinciding with the direction of surface water flow. The validation result of 82.08% confirms the very good agreement among the groundwater record data and groundwater potential classes delineated. Thus, the identification of GWPZ by using GIS and RS through AHP is reliable for conducting similar studies.
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    GROUNDWATER POTENTIAL MAPPING USING GIS AND REMOTE SENSING: A CASE STUDY IN WEYIB SUB-BASIN, GENALE-DAWA RIVER BASIN, SOUTHEAST ETHIOPIA
    (Hawassa University, 2021-08-12) ABDULGEFAR MUHIDIN MOHAMMED
    To fulfill the demand of a rapidly growing population in drought-prone areas with high rate of urbanization, identification and management of groundwater resources are required. In the Weyib Sub-basin, a search for an alternative source of water has been always a major issue. The current practice of groundwater potential zone (GWPZ) identification is time-consuming and uneconomical. Therefore, it is required to apply effective techniques for proper evaluation of groundwater resources. This study applied integration of GIS-Remote Sensing (RS) and Analytical Hierarchy Process (AHP) for mapping the GWPZ of Weyib Sub-basin, Southeast Ethiopia. For this purpose the physiographic, geology and climatic factors influencing GWPZ of the study area were characterized. The thematic maps of geomorphological landforms, lineament density, geology, rainfall distribution, drainage density, elevation, slope, LU/LC and soil texture were prepared. System for automated geoscientific analysis (SAGA) GIS, PCI Geomatics, Rockworks 16, IDRISI Selva and Surfer 17.1, were employed for landform classification, lineament extraction, rose diagram preparation, pairwise comparison of the factors and identification of groundwater flow direction, respectively. The AHP technique of Multi-criteria decision analysis (MCDA) was employed to determine the relative weight and influences of the thematic layers. Geomorphologic landform, lineament density, geology, and rainfall distribution were found to be the dominant factors sharing the highest weightage of 67%. A weighting overlay approach of GIS was utilized to overlay the thematic maps. The resulting GWPZ of the study area indicates five zones representing very high, high, moderate, poor and very poor GWPZ. The areal extent of very high and high GWPZ is 41 km2 and 2032 km2, respectively. Moderate, poor and very poor GWPZ covers 2088 km2, 252 km2 and 0.142 km2 areas. The particular direction of groundwater flow is towards the NE and SE, coinciding with the direction of surface water flow. It was controlled by NW-SE striking geologic structures. The delineated GWPZ map is verified by using the existing water point’s inventory data. It indicates a good prediction accuracy of 84%. Thus, the identification of GWPZ by using GIS and RS through AHP is reliable for conducting similar studies