Department of Geology

Permanent URI for this collectionhttps://repository.mu.edu.et/handle/123456789/207

Browse

Search Results

Now showing 1 - 5 of 5
  • Item
    GROUNDWATER POTENTIAL AND WELL YIELD DISCREPANCIES: HYDROGEOLOGICAL CONTROLS, DRILLING CHALLENGES, AND AQUIFER PARAMETER–RESISTIVITY RELATIONSHIPS IN UPPER BILATE RIVER BASIN, MAIN ETHIOPIAN RIFT VALLEY, SOUTHERN ETHIOPIA
    (Mekelle University, 2025-10-16) Fisseha Teka Hailu
    Discrepancies in well yields within the Upper Bilate River Basin (UBRB) of the Ethiopian Rift Valley Lake Basin highlight the intricate hydrogeology of its volcanic aquifers and Quaternary deposits. This study examines the influence of drilling-challenges such as partial penetration, well loss coefficient, wellbore storage on yield variations, which may surpass the effects of natural hydrogeological variability. By integrating data from meteorological, hydrological, remote sensing, vertical electrical sounding, and pumping tests with historical well records, key aquifer parameters like transmissivity and hydraulic conductivity are quantified, while empirical relationships between aquifer productivity and resistivity are established. This study's water balance analysis for the Upper Bilate River Basin reveals a semi-humid system with a 254.6 mm annual surplus. A significant wet-season surplus facilitates groundwater recharge, estimated at 58.9 mm/year (6% of rainfall), indicating moderate infiltration and strong surface water-groundwater interaction A hydrogeological framework and groundwater potential zone map, generated through weighted overlay analysis of ten thematic layers, categorized the basin into excellent (1.39%), very good (17.9%), good (79.17%), and low (1.54%) potential zones. Most wells align with high-potential zones, confirming predictive accuracy: 74% of Wells are in very good zones and 26% in good zones, with none in low-potential areas. Transmissivity (T) in the study area varies from 0.05 to 841.10 m²/day, indicating a heterogeneous aquifer system. Moderate to moderately high transmissivity zones (59.77–89.93 m²/day) dominate, covering nearly 60% of the area, mainly in the central and northern parts, suggesting good aquifer productivity. Geophysical investigations identify Layer 6 (highly weathered and fractured pyroclastic rocks) as the most promising aquifer, followed by Layers 5 and 4, while upper shallow layers function as aquitards. A strong correlation between transmissivity and transverse resistance (r = 0.83, p = 1.32×10⁻¹³) supports the integration of geophysical and pumping test data for aquifer assessment. Well yield discrepancies in the UBRB are influenced more by drilling challenges than by aquifer natural heterogeneity. An analysis of 220 Wells indicates a partial penetration ratio (L/b) of 0.13 to 0.96, with a mean of 0.56, suggesting moderately penetrating wells. Wellbore storage shows that 49% of wells have high storage (Cw ≥ 0.9), while 27% have low storage (Cw < 0.1), reflecting variable aquifer connectivity. In a study of 25 wells, loss coefficients (C) range from 4.0×10⁻⁷ to 5.0×10⁻⁵ day²/m⁵, with 72% classified as severely clogged and none being properly developed. Well efficiency varies between 11.2% to 100% (mean 70.3%), with 18% rated Poor, 22% Fair, 30% Good, and 30% Excellent. This highlights the need for better well design, development, and maintenance practices. The correlation between transmissivity and well efficiency demonstrates that aquifer transmissivity primarily governs well performance, with high-transmissivity zones hosting the most efficient wells. In contrast, low efficiency in moderately transmissive areas mainly stems from technical issues—such as improper well design, partial penetration, or excessive wellbore storage rather than aquifer limitations. Enhancing well construction and maintenance practices is therefore crucial to fully realize groundwater potential in these zones.
  • Item
    GROUNDWATER POTENTIAL ASSESSMENT OF AGULAE CHINFERS RIVER CATCHEMNT, NORTHEN ETHIOPIA
    (Mekelle University, 0011-10-25) Hadush weldemichaeal
    The general objective of the research is to study the hydrogeological system of the Agula-Chinferes catchment by giving particular emphasis to groundwater potential assessment, and recharge-discharge conditions. The Agulae_Chinfers river catchment is found in the Tigray National Regional state, Northern Ethiopia, which is about 783km from Addis Ababa on the way between Mekelle and Wukro in the western part of Giba Basin. It has a total area of 697 km2 with altitude ranging from 1769 m to 2853 m above mean sea level. The area is covered by alluvial deposit, dolerite rocks, limestone-shale-marl intercalation, limestone, adigrat sandstone, enticho sandstone and meta -volcanic. These rocks mainly meta- volcanic and adigrat sandstone in composition are emplaced along an NW-SE tectonic lineament. Different approaches are used to estimate the groundwater recharge, characterize the aquifer and assess the hydro geochemistry of the catchment. Soil moisture balance, and surface water balance approaches are used to estimate recharge. Annual precipitatrion by estimated arithmetic mean is 632mm/year, by Theissen polygon 626.3mm/year,by Ishyetal method 630.84mm/year,potential evapotranspiration by Penman method 815.97mm/year, potential evapotranspiration by Thornwaite method 817.41mm/year, average by two methods 816.7mm/year and the actual evapotranspiration by Turc method 339.14mm/year, Thornthwaite and Mather standard soil water balance model 458.5mm/year The results of estimated annual direct groundwater recharge in the catchment shows that the recharge estimated by soil moisture balance 54.7mm/year .the recharge estimated by water balance 45.34mm/year,average from two methods 50.02mm/year ( 8% of the precipitation in the watershed) .So, the recharge estimated by soil moisture balance is higher than the values estimated by water balance method. The groundwater potential and surface water (drainage pattern) and the discharge recharge is controlled by the topography, the geology, and structure. In the limestone, limestone-shale-marle intercaltion and sandstone rocks, which are the major aquifers in the area the hydraulic parameter varies with the fracture distribution. The structures that control the recharge discharge condition and areas of groundwater potential are associated with the regional tectonic structures of the faults. The source and alignment of springs is also associated with the joints, fractured and hill said. Geology, land use and land cover, soil types, dreaning density, linamant density, rainfall and slope are used to show groundwater potentioal zones and groundwater flow system, recharge discharge conditions. The analysis result of the above parameters overlaps with the hydrogeology which indicates that the south -eastern, eastern and northwestern part of the area is the potential zone for ground water exploitation. Piper plots are used to classify the water chemistry. There is variation in water type from low TDS Ca-HCO3 and Ca-Mg-HCO3 through intermediate type Ca-Na-HCO3 to high TDS Na-HCO3 type. There is no strong variation in PH of the waters as such and the low TDS, low alkalinity, waters have similar near neutral PH with the high TDS, high alkalinity water, reflecting the existence of chemical reaction that affect the hydrogen ion.PH of the study area(6.56-7.95),groundwater of the study area based on total dissolved solids (by WHO standard) fresh water (238-1000mg/l) and brackish water (1000-1469.6mg/l) so, the groundwater of the area has Total Dissolved Solids ranging from less than 615.41 mg/l in the high lands (recharge area) and sandstone geological formation to about 1469.6mg/l in low lands especially in areas of limestone intercalation with shale-marl geological formation. The total Hardens of the study area range from 85.2 to 947 (mg/l). so, by the classification of water (Jasrotia & Kumar, 2014) from medium hard to very hard (in areas of limestone intercalation with shale-marl geological formation .
  • Item
    Evaluation Of Limestone as Coarse Aggregate in Concrete and Cobblestones: A Case study from Mekelle Area, Northern Ethiopia
    (Mekelle University, 2024-11-25) Muez Aregawi
    Engineering geological investigation is essential for evaluating the quality of construction materials and ensuring the durability of engineering structures. This study assessed the physical and mechanical properties of limestone aggregates from selected quarries in the Mekelle area to determine their suitability for concrete and stone-paved road applications. A total of twelve representative samples and 50 kg of coarse aggregates were collected according to ASTM D75 from the Shugala, Kokolo, Mayalem, Mossobo, Chanadug, and Genha quarry sites and tested for gradation, specific gravity, unit weight, water absorption, moisture content, flakiness index (FI), aggregate crushing value (ACV), Los Angeles abrasion value (LAAV), and unconfined compressive strength (UCS), with results compared to ASTM and BS standards. The results indicate that the tested aggregates largely satisfy international specifications. Specific gravity values ranged between 2.43 and 2.83, while unit weight varied from 1.47 to 1.65 g/cm³. According to ASTM C33 classification, these unit weight values confirm that the aggregates are normal weight. Water absorption values (0.11%–0.78%) fall within the required range, indicating low porosity and good durability. Moisture content is very low (0.012–0.39%), significantly below the 4% limit, ensuring that the aggregates are dry. Mechanical tests revealed flakiness index values ranging from 12.11–20.30%, ACV values from 10.66–22.16%, LAAV values from 19.18– 25.40%, and UCS values from 105–117 MPa, indicating that all samples fall within the “highstrength” category (>55 MPa). Sieve analysis further revealed that aggregates from Chanadug, Genha, Mossobo, and Mayalem quarries exhibit favourable particle size distribution, making them highly suitable for construction, while those from Shugala and Kokolo did not meet gradation criteria.
  • Item
    HYDROMETEOROLOGICAL STATIONS DISTRIBUTION AND PARAMETER TRENDS IN TIGRAY.
    (Mekelle University, 2025-09-25) MEBRAT AMARE
    The effective management of water resources in Ethiopia's topographically complex Tigray Region is critically dependent on a robust hydro-meteorological observation distribution. However, the existing distribution suffers from severe deficiencies in spatial coverage and operational integrity, creating significant uncertainty for water resource planning. This thesis provides a systematic evaluation of the hydro-meteorological distribution in Tigray, analyzes long-term trends in key climatic and hydrological parameters, and proposes a data-driven framework for its optimization. The study employed a mixed-methods design, integrating Geographic Information Systems (GIS) to assess spatial adequacy against World Meteorological Organization (WMO) standards, non-parametric statistical tests (Mann-Kendall, Sen’s Slope) to analyze long-term (1960–2024) data, and field verification to assess operational status. Results reveal a network in critical failure. The conventional station network meets only 51% of the WMO minimum requirement, with precipitation stations achieving just 17% of the necessary coverage. This spatial gap is compounded by an operational collapse, with only 13% of the required stations currently functional, creating vast unmonitored areas. The streamflow gauging network is similarly sub-optimal, while the modern Automatic Weather Station (AWS) network is nascent. Trend analysis identified no significant long-term change in regional rainfall or streamflow. In conclusion, the existing monitoring infrastructure is structurally imbalanced, spatially biased, and operationally crippled, rendering it unfits to support reliable water resource assessment or climate-resilient development. This thesis culminates in a strategic roadmap with prioritized recommendations for the phased expansion and modernization of the network to build a scientifically robust observational foundation for the region.
  • Item
    Landslide Susceptibility Mapping Using Frequency Ratio (FR) and Weight of Evidence (WoE) Methods, and Verification Using the Limit Equilibrium (LE) Method: A Case Study along the Bonga - Felegeselam Road.
    (Mekelle University, 2025-09-25) Hagos Kidanemariam Gebregewergs
    Landslides are a critical geohazards in Ethiopia, particularly along mountainous and rift-margin road corridors, where they frequently disrupt transportation, damage infrastructure, and pose serious threats to human life. The study aims to generate landslide susceptibility mapping and slope stability analysis along the Bonga – Felegeselam road corridor. Initially, a total of 120 landslides were inventoried and mapped based on field visits and Google Earth image interpretation, and subsequently divided into two subsets: 70% for model training and 30% for validation. Eight landslide causative factors including slope angle, aspect, elevation, lithology, land use, distance to road, distance to stream and precipitation were selected based on geomorphological relevance and site verification. The relationship between landslide occurrence and causative factors was analyzed using frequency ratio (FR) and weight of evidence (WoE) models. Based on these models, landslide susceptibility maps were generated by integrating the weighted values of all factors and reclassified into five susceptibility zones: very low, low, moderate, high, and very high. The high and very high susceptibility zones accounted for 17.8% and 24.1% of the area in the FR and WoE models, respectively. The accuracy of the models was validated using the relative operating characteristic (ROC) curve and the area under the curve (AUC) values. The frequency ratio (FR) model achieved a prediction rate of 80.6%, while the WoE model yielded 79.1%, both indicating strong predictive capability. Geotechnical verification of eight road slope failures within moderate to very high susceptibility zones was performed using limit equilibrium method (LEM) based stability analyses. Secondary borehole and eight test pit data, supported by laboratory test results, were used to establish subsurface profiles and geotechnical parameters of the slope materials. Stability analyses using Bishop and Spencer methods under both dry and saturated conditions produced factors of safety ranging from 1.15 to 0.78 and 0.96 to 0.54, respectively. These results confirm the consistency of the susceptibility models by indicating strong agreement between mapped zones and stability analysis results. This approach provides a strong framework for landslide hazard management and informed infrastructure planning in Ethiopia and similar mountainous regions.