Gebremedhin Berhane | Ghent University (original) (raw)

Papers by Gebremedhin Berhane

Journal of African Earth Sciences, Aug 1, 2021

The hilly region of Manipur especially along the NH-39 road, which is the lifeline of the State, ... more The hilly region of Manipur especially along the NH-39 road, which is the lifeline of the State, is prone to landslides every year particularly during the monsoon season. Anthropological factors, such as excessive deforestation, unsystematic changes in land use and land cover pattern and slope cultivation, etc. are indirectly initiate the process of landslides. In the present study, landslide susceptibility mapping was carried out using frequency ratio and fuzzy gamma operator models with the help of geomatics techniques. The landslide susceptibility mapping was prepared using landslide inventory data and nine landslide causative factors, i.e. lithology, land use and land cover, geomorphology, drainage density, lineament density, slope gradient, slope aspect, curvature, and elevation. These causative factors were prepared with the help of toposheet, high resolution IRS P6 LISS IV satellite imagery, cartosat DEM data and extensive field work. The landslide susceptibility maps were prepared by calculating the relationship between the landslide causative parameters with landslide areas using a frequency ratio model. To get the fuzzy membership values, the frequency ratio values were normalized between the ranges of 0 and 1. The landslide susceptibility maps were compared and prediction accuracy of both the models was derived using the area under curve (AUC) method. The success rate curves were obtained using both training and all landslide inventory dataset. For training landslide inventory dataset, the AUC value of the success rate curve for the frequency ratio model was found to be 0.8056, whereas for the fuzzy gamma operator (using c = 0.99) model, it was calculated as 0.9150. In the case of all landslide inventory dataset, the AUC value of the success rate curve for the frequency ratio model and the fuzzy gamma operator model were 0.7921 and 0.8188, respectively. The landslide susceptibility index was also compared with the landslide validation inventory dataset to obtain the prediction rate curves. The AUC value of the prediction rate curve for the frequency ratio model was 0.5681, whereas in the case of the fuzzy gamma operator model, it was 0.6721.

Momona Ethiopian Journal of Science

Leakage is one of the major problems facing the functionality and sustainability of dams. It occu... more Leakage is one of the major problems facing the functionality and sustainability of dams. It occurs through the embankment body, reservoir, foundation, and abutments. This study was conducted to identify the main causes of the leakage problem at the Dora-1 dam, located in the northern part of Ethiopia. It is an earthfill dam with a height of 43.5 m, crest length of 454 m, and reservoir capacity of 4.67 million cubic meters. Part of the embankment body was wet and swampy up to 20 m high from the ground due to leaking water. Geological investigation, laboratory test of the construction materials (including grain size analysis, specific gravity and water absorption, Atterberg limit, free swell, dispersion, permeability, and shear strength), and electrical resistivity investigation were used to identify and pinpoint the possible causes of the leakage problem. Results of the study show that the favorable geological features responsible for the occurrence of leakage include: (a) geologica...

Rainwater-Smart Agriculture in Arid and Semi-Arid Areas, 2017

In Tigray, over 78,000 dugout ponds have been constructed since 2000. The objective was to allevi... more In Tigray, over 78,000 dugout ponds have been constructed since 2000. The objective was to alleviate the problem of recurrent drought that prevails in the region every five to ten years. However, it has been reported that most of the ponds are not functional. Therefore, this paper presents an assessment of the dugout pond construction in Tigray with a particular emphasis to challenges and technical problems and pinpoints the causes that led to the poor performance of the ponds. Thus, even though rainwater harvesting ponds have the potential to ensure availability of water for various uses and generate income for smallholders, poor performance levels and insufficient impacts to local communities were widely observed in the study area due to inadequate site selection, absence of biophysical survey during design and construction, leakage and evaporation losses, and poor management of the ponds.

Hydro Nepal: Journal of Water, Energy and Environment, 2019

Construction of underground Cavern in the Himalayan region is full of challenges and uncertaintie... more Construction of underground Cavern in the Himalayan region is full of challenges and uncertainties. Experience has shown that construction in Himalayan regions requires good understanding of geology, adequate site investigations, proper design and selection of suitable construction methodology and technology. The most commonly encountered geological problems during excavation of underground structure in Hydroelectric Projects are, Fault/Thrust/Shear Zones squeezing and swelling, wedge block failure etc. Tehri Pumped Storage Plant (PSP) is located at the left bank of river Bhagirathi in the state of Uttarakhand in Northern India. This case study indicates about the geological challenges faced and their remedial measures during the construction of Tehri PSP Powerhouse Cavern having dimension of 203m x 24m x 58m.3D-geological mapping with 1:100 scales was carried out in excavated central drift of powerhouse to evaluate the rock composition, behavior of rock mass, structural features an...

Momona Ethiopian Journal of Science, 2013

Surface and groundwater chemistry being an important factor in urban planning and infrastructure ... more Surface and groundwater chemistry being an important factor in urban planning and infrastructure development, present paper tries to present the problems of corrosiveness due to groundwater chemistry in Mekelle city. Iron corrosion in distribution systems and engineering structures are common problems in many urban areas. Corrosiveness of groundwater at different localities in Mekelle and its environs has been evaluated on the basis of AAS-UV spectrophotometer-generated hydro-geochemical data. Corrosiveness of water was estimated by using corrosion indices like Larson Index, LI and Aggressive Index, AI and total dissolved solids, total carbonate hardness, chloride and sulphate data were evaluated to estimate aggressiveness of the water samples on iron pipes. Analyses of the results have shown that most of the samples from boreholes and hand dug wells compared to spring samples, are potentially aggressive. The result shows that 66.7% spring, 81.3% shallow hand dug wells and 81% borehole water samples have a Larson index (LI) above 0.5, a threshold of corrosiveness of water. This study highlights the basic characteristics of surface and groundwater chemistry and its potential hazard for corrosion of pipes, and provides a baseline information and awareness to the city planners for urban management.

Abstract: Engineering geological map of Mekele town and its environs has been established for the... more Abstract: Engineering geological map of Mekele town and its environs has been established for the first time after characterizing the geotechnical property of soils and rocks in the field and laboratory. Geological, geotechnical and engineering geological condition of Mekele area was characterized in relation to their effects to civil engineering structures. The engineering geological and geotechnical condition of the rocks and soils was studied on the bases of field description, simple in-situ geotechnical test and laboratory analysis. The dominant lithologic units are Quaternary sediment deposits (alluvial and residual soils), dolerite, sandstone, limestone-marl-shale intercalation and bedded limestone. The laboratory tests revealed that soils have medium to very high plasticity. The liquid limit of the soils varies from 50-80.8% for alluvial; 29.4-67% for residual. The dolerite shows variable engineering property in terms of strength from weak rock mass strength to very high rock...

ABSTRACT The study was conducted to assess the main causes of leakage problem in the Hashenge mic... more ABSTRACT The study was conducted to assess the main causes of leakage problem in the Hashenge micro-dam, located in the Tigray regional state, northern part of Ethiopia. The micro dam is a 19 m height earth fill dam with the length of 387 m and reservoir capacity of about 2.3 million cubic meters at maximum water level. Geological, geophysical and engineering geological investigations were conducted in the abutment and reservoir area to assess and pinpoint the main causes. The dominant lithologic units include limestone-shale-marl intercalation, dolerite and recent soil deposits. Vertical electrical sounding was used to locate geotechnical boreholes and to know vertical and lateral variability of geological materials. Geotechnical and engineering geological investigation including drilling of three boreholes and packer testing along with detail measurement and analysis of discontinuity parameters was conducted. Analysis of the data shows that the sedimentary succession, limestone-sh...

The study was conducted to assess the index properties and characterize soils and rocks of Mekele... more The study was conducted to assess the index properties and characterize soils and rocks of Mekele town located in the northern Ethiopia having an area of 45 km2. Geological, engineering geological and geotechnical condition of the rocks and soils was studied on the bases of field description, in-situ geotechnical test and laboratory analysis. Four soil types were identified in the field: clay, silt, sandy clay/silt and clayey/silty sand soils. Laboratory result revealed that moisture content of the soils ranges from 15.8 to 40.9% for clay; 21.7 to 34.7% for silt; 6.6 to 20.5% for sandy silt/clay and 14.2 to 23% for clayey/silty sand soils. pH and electrical conductivity of the soils vary from 7.1-8.5 and 180-1930μS/cm, respectively. The liquid limit (LL) in percent ranges from 29-59, 50-67.4, 37.5-70.8 and almost non-plastic to 66 for clay, silt, sandy clay/silt and clayey/silty sand, respectively. Similarly, the plasticity index in percent (PI) of the soils ranges from 14-36.6, 13....

Journal of the Geological Society of India, 2014

The hilly region of Manipur especially along the NH-39 road, which is the lifeline of the State, ... more The hilly region of Manipur especially along the NH-39 road, which is the lifeline of the State, is prone to landslides every year particularly during the monsoon season. Anthropological factors, such as excessive deforestation, unsystematic changes in land use and land cover pattern and slope cultivation, etc. are indirectly initiate the process of landslides. In the present study, landslide susceptibility mapping was carried out using frequency ratio and fuzzy gamma operator models with the help of geomatics techniques. The landslide susceptibility mapping was prepared using landslide inventory data and nine landslide causative factors, i.e. lithology, land use and land cover, geomorphology, drainage density, lineament density, slope gradient, slope aspect, curvature, and elevation. These causative factors were prepared with the help of toposheet, high resolution IRS P6 LISS IV satellite imagery, cartosat DEM data and extensive field work. The landslide susceptibility maps were prepared by calculating the relationship between the landslide causative parameters with landslide areas using a frequency ratio model. To get the fuzzy membership values, the frequency ratio values were normalized between the ranges of 0 and 1. The landslide susceptibility maps were compared and prediction accuracy of both the models was derived using the area under curve (AUC) method. The success rate curves were obtained using both training and all landslide inventory dataset. For training landslide inventory dataset, the AUC value of the success rate curve for the frequency ratio model was found to be 0.8056, whereas for the fuzzy gamma operator (using c = 0.99) model, it was calculated as 0.9150. In the case of all landslide inventory dataset, the AUC value of the success rate curve for the frequency ratio model and the fuzzy gamma operator model were 0.7921 and 0.8188, respectively. The landslide susceptibility index was also compared with the landslide validation inventory dataset to obtain the prediction rate curves. The AUC value of the prediction rate curve for the frequency ratio model was 0.5681, whereas in the case of the fuzzy gamma operator model, it was 0.6721.

Natural constraints and the damaged Meli gold mining: forecasting impact on the water resources q... more Natural constraints and the damaged Meli gold mining: forecasting impact on the water resources quality of the Meli area and the surroundings, Tigray Kaleab Adhena Abera 1, Berhane Abrha 2, Tesfamichael Gebreyohannes 2, Abdelwassie Hussien 2 , Miruts Hagos 2, Gebremedhin Berhane 2, and Kristine Walraevens 11 Laboratory for Applied Geology and Hydrogeology, Department of Geology, Ghent University, Belgium (kaleabadhena.abera@ugent.be)2 Department of Geology, School of Earth Science, Mekelle University, Ethiopia : Meli is the only modern gold mining site in the Tigray region, Northern Ethiopia. Water resources of this area and the surroundings are currently very susceptible to pollution by toxic chemicals than ever before, due to both the natural geological setup of the area and anthropogenic impacts, specifically because of the recent war in northern Ethiopia. The war that was started on November 03, 2020, resulted in the complete destruction of the mining company and tailings da...

Momona Ethiopian Journal of Science, 2021

Due to the ever-increasing demand for water in Aynalem catchment and its surrounding, there has b... more Due to the ever-increasing demand for water in Aynalem catchment and its surrounding, there has been an increased pressure on the Aynalem well field putting the sustainability of water supply from the aquifer under continuous threat. Thus, it is vital to understand the water balance of the catchment to ensure sustainable utilization of the groundwater resource. This in turn requires proper quantification of the components of water balance among which recharge estimation is the most important. This paper estimates the groundwater recharge of the Aynalem catchment using high-resolution hydro-meteorological data. Daily precipitation and temperature measurement data for years 2001-2018; groundwater level fluctuation records collected at every 30 minutes; and soil and land use maps were used to make recharge estimations. In the groundwater level fluctuation, three boreholes were monitored, but only two were utilized for the analysis because the third was under operation and does not repr...

International Journal of Earth Sciences, 2020

The Mekelle basin (area ~ 5500 km 2) is located at the immediate western margin of the Afar Depre... more The Mekelle basin (area ~ 5500 km 2) is located at the immediate western margin of the Afar Depression, which has a history of collision, subsidence, uplift, magmatism and now rifting. The evolution of such small to medium size basins as the Mekelle in a complicated geodynamic setup is a subject of debate, because several different mechanisms of basin formation could apply. To address the possible basin evolution scenarios, we combine structural and dynamic analyses of northern Ethiopia, with strong emphasis on the basin and basin bounding basement rocks. The northern basin bounding block is uplifted by about 1500 m compared with the western and southwestern basin-bounding blocks. In the basin, superposition of large-scale orthogonal brittle shear fabrics and the development of young, parallel to subparallel extensional fractures and domino faulting have produced a total of ~ 2200 m vertical displacement. These observations, coupled with the absence of gradual roll-down of the internal basin (i.e., absence of bending/folding of an elastic beam supported at both ends), imply that Mekelle basin is not an IntraCONtinental Sags (ICONS) or plate interior basin, as previously described, but is instead a multi-tectonic triggered basin. Integrated satellite images using ground-controlled measurements and deep borehole data were used to decipher the entire evolution of the basin starting from the late-collisional deformation through the regional up-doming to the sills/dikes injection and basin formation.

Bulletin of Engineering Geology and the Environment, 2020

Landslides, mainly triggered by rainfall, are one of the most common natural hazards in the north... more Landslides, mainly triggered by rainfall, are one of the most common natural hazards in the northern and central highlands of Ethiopia, resulting in the loss of human life and property. As part of the Ethiopian highlands, Mgulat Mountain (88.6 km 2) is a typical example for the occurrence of landslides and associated damages. The main aim of this research was to generate landslide susceptibility map (LSM) for the first time by considering various causative factors typical for the Mgulat Mountain area. The methods used include frequency ratio (FR) and kinematic analysis (KA) supported by GIS tools. The research involved conventional fieldwork (e.g., geological mapping, landslides inventory) and analysis and interpretation of images. From the geological mapping, major rock units were identified: quaternary deposit, basalt, red sandstone, tillite, and white sandstone. A total of 220 landslides (15.45 km 2) were identified in the study area from field survey, Google Earth and aerial photo interpretation. Five causative factors (lithology, slope steepness, distance from drainage, land use-land cover (LULC), and slope aspect) were selected based on their contribution to landslide initiation as the landslide conditioning factors for generation of the LSM. From the five causative factors, lithology and slope steepness were found to be influential as landslide conditioning factors. Specifically, lithology (red sandstone and tillite), distance to stream (0 to 300 m), LULC (bare land and settlement), and slope steepness (> 25°) have FR > 1, indicating a high relationship with landslide occurrence. Based on the generated LSM, five susceptibility classes or zones were identified (very low, low, moderate, high, and very high susceptibility). The area of each class as percentage of total area was found to be 19.53, 24.15, 22.57, 18.74, and 15.01%, for the very low to the very high class, respectively. The results of KA show potentially and marginally planar, topple, and wedge failures. The generated LSM can serve as an important tool or guide for further land-use planning and to prevent and mitigate landslide-related risks. Consequently, to consider cost-effective and technically sound mitigation measures, detailed and site-specific multidisciplinary investigations are recommended.

Environmental Earth Sciences, 2017

Overextraction of groundwater is widely occurring along the coast where good quality groundwater ... more Overextraction of groundwater is widely occurring along the coast where good quality groundwater is at risk, due to urbanization, tourist development and intensive agriculture. The Sabratah area at the northern central part of Jifarah Plain, Northwest Libya, is a typical area where the contamination of the aquifer in the form of saltwater intrusion, gypsum/anhydrite dissolution and high nitrate concentrations is very developed. Fifty groundwater samples were collected from the study area and analysed for certain parameters that indicate salinization and pollution of the aquifer. The results demonstrate high values of the parameters electrical conductivity, sodium, potassium, magnesium, chloride and sulphate which can be attributed to seawater intrusion. The intensive extraction of groundwater from the aquifer reduces freshwater outflow to the sea, creates drawdown cones and lowering of the water table to as much as 30 m below mean sea level. Irrigation with nitrogen fertilizers and domestic sewage and movement of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for the high nitrate concentration towards the south of the region. Seawater intrusion and deep salt water upconing result in general high SO 4 2concentrations in groundwater near the shoreline, where localized SO 4 2anomalies are also due to the dissolution of sebkha deposits for few wells in the nearby sebkhas. Upstream, the increase in SO 4 2concentrations in the south is ascribed to the dissolution of gypsum at depth in the upper aquifer.

Environmental Earth Sciences, 2017

The desert of eastern Libya forms one of the most arid regions of the Sahara. Libya suffers from ... more The desert of eastern Libya forms one of the most arid regions of the Sahara. Libya suffers from a shortage in water resources due to its arid climate. On the other hand, Libya has large resources of good-quality groundwater distributed in six basin systems beneath the Sahara. In order to deal with the shortage of water in most coastal cities, the Libyan government established the Great Man-Made River Project to transport millions of cubic meters of water a day from desert wellfields to the coastal cities, where over 80% of the population lives. In this paper, a hydrogeochemical study is presented for the Nubian Sandstone Aquifer in Tazerbo Wellfield, SE Libya, based on chemical analyses and physical parameters for 108 wells. Samples were collected from 108 borewells of the Nubian Aquifer (Akakus Formation) from depth range between 280 m in the north and 500 m in the south. This study is the first hydrochemical investigation in Tazerbo and also in the whole Sahara, which introduces the importance of considering the end members and the synsedimentary influence for the interpretation of the groundwater hydrochemistry. The results of the analyses indicate soft to moderately hard, lowly mineralized, slightly alkaline groundwater, with Mg 2? as the main cation and HCO 3 as the main anion. The major hydrogeochemical processes that affect the quality of water in sediments of the Nubian system at Tazerbo have been identified; the water type is mostly fresh MgHCO 3, while NaHCO 3 and KHCO 3 are also found for some wells. These water types indicate that groundwater chemistry is changed by cation exchange reactions during flushing of the aquifer by freshwater from the south.

Journal of African Earth Sciences, 2017

Highlights  Geological factors considered into account in reservoir water leakage.  Vertical el... more Highlights  Geological factors considered into account in reservoir water leakage.  Vertical electrical sounding and profiling integrated with other data for leakage zone delineation.  Discontinuities, bedding planes and regional faults play a great role in leakage problems localized in sedimentary basins.  Regional and local geology and hydrogeology have played a major role in the planning, design, construction and performance of the MDRs. Geological and geophysical investigation of water leakage from two micro-dam reservoirs: implications for future site selection, northern Ethiopia

Environmental Earth Sciences, 2016

Large increases in water demand with very little recharge have strained Libya's groundwater resou... more Large increases in water demand with very little recharge have strained Libya's groundwater resources resulting in serious declines in water levels and quality, especially along the Mediterranean coast where most of the domestic, industrial and agricultural activities are concentrated. The rapid economic expansion, coupled with sharp population growth, in the Jifarah Plain comprising Tripoli, NW-Libya, has created an immediate need for proper groundwater reserves, not only to meet the increasing population's demands, but also to secure a contingency plan. The main problem is salinization of freshwater. Based on the available hydrogeological and hydrochemical information, the sources of salinization are identified. The overpumping for groundwater contributed to the deterioration of the water quality by seawater intrusion and exposing the deep saline water. Clis the major pollutant of the aquifer. Water samples were collected from 134 sampling wells in the study area and analyzed for the major cations and anions. The chemical results for the groundwater samples in the plain are classified according to the Stuyfzand groundwater classification system. The water type is mostly CaCl, NaCl and Ca/MgMix. These water types indicate that groundwater chemistry is changed by cation exchange reactions during the mixing process between freshwater and seawater. The majority of groundwater samples (80%) show a composition that is indicative of seawater intrusion.

Environmental Earth Sciences, 2012

The study was conducted in the rapidly expanding city of Mekelle located in the northern part of ... more The study was conducted in the rapidly expanding city of Mekelle located in the northern part of Ethiopia, East Africa. An integrated approach including geomorphological, geological and engineering geological, geotechnical and hydrogeological methods were used to characterize the natural urban environment to be used as a baseline for protection and rational planning of development. Conventional field observation, test pits and drilled boreholes were used to collect soil, rock and water samples and standard laboratory procedures were applied. The results revealed that the main geologic constraints to sustainable development of the city are active erosion, instability of slopes, flood hazard, cyclic/alternating hard and weak rock layers, high swelling-shrinkage soils, shallow and unconfined groundwater with variable composition and high susceptibility to corrosion and pollution. It is recommended to avoid development and expansion of the city in areas of steep land forms, at the foot of steep slopes and in areas covered by black alluvial soil deposits. Development of a systematic multidisciplinary database aided by GIS, with continuous monitoring and updating is also highly recommended and will be useful for further refined geotechnical microzonation. It is the authors' belief that this study highlights the basic constraints and hazards the city is facing, and provides baseline information and awareness to the city planners, decision makers, geo-environmentalists, engineers and the community for future expansion and rehabilitation plans and to tackle the existing hazards.

Land Degradation & Development, 2015

Mendae Plain at Abraha Atsbaha (Tigray Region, northern Ethiopia) is an agricultural area, which ... more Mendae Plain at Abraha Atsbaha (Tigray Region, northern Ethiopia) is an agricultural area, which has been very drought-prone in the past. In the last decade, agricultural development has boosted because of the intensive use of large diameter wells that tap the phreatic aquifer. Pumped water is used for irrigation during the long dry season (October to May). Since 15 years, water harvesting measures have been implemented, mainly in the form of infiltration ponds and trenches that enhance local infiltration of rainfall runoff from hillslopes. To investigate the sustainability of the groundwater exploitation and the efficiency of the measures, the different recharge and discharge components of the water balance of data-scarce Mendae Plain have been identified and quantified, using different methods. Diffuse aquifer recharge is calculated from a soil moisture balance, based on meteorological data, and with the chloride mass balance method, based on groundwater analyses. Diffuse recharge is much higher on cultivated land plots than on non-cultivated bare soils. Rainfall infiltration in ponds and trenches is estimated based on the inflow catchment derived from the topography. Groundwater flow to a nearby river is obtained by balancing inflow and outflow by the other components over an 11 year period. The balance components are integrated into a lumped parameter model that was run for the period from 2000 to 2010. The results show that infiltration in ponds and trenches contributes between 30 and nearly 50% of total aquifer recharge, with the highest values in dry years. Changes in aquifer storage over time are an indicator for the evolution of groundwater levels in the aquifer and confirm the occurrence of two dry periods in

Journal of African Earth Sciences, 2013

Millions of people throughout the world depend on dam reservoirs for domestic water supply, irrig... more Millions of people throughout the world depend on dam reservoirs for domestic water supply, irrigation, electricity and flood protection. In the last two decades, 54 micro-dam reservoirs have been constructed in Northern Ethiopia to fight the recurrent drought and improve agricultural productivity through irrigation. However, about 60% of these micro-dam reservoirs are suffering from excessive leakage. Comprehensive studies have been carried out on two micro-dams to assess and pinpoint the causes of leakage. Arato and Hashenge micro-dams located in Northern Ethiopia have 20 m and 19 m height, and 2.59 Mm 3 and 2.23 Mm 3 reservoir capacities respectively. Observational geological description, shallow hand dug test pits, vertical electrical sounding and drilling of geotechnical holes were used to understand the overall geological, engineering geological and geo-hydrological setup of the area. The different methods applied, such as discontinuity analysis, geophysical surveys, drilling and packer tests, delivered results that were found to be in close agreement and led to the identification of the leakage zone. The geological units found in both sites are limestone-shale-marl intercalation, dolerite and recent soil deposits. The research results revealed that the limestone-shale-marl intercalation unit is heterogeneous and shows alternating sequences. Analysis of the different data shows that the limestone-shale-marl intercalation is a pervious unit (hydraulic conductivity in the range of 10 À4-10 +2 cm/s) and was found to be responsible for the excessive leakage of the micro-dams. It is hoped that the observations, data and insights gathered from these case studies will enable to plan technically and economically viable anti-leakage measures for these schemes and help for future new site selection and design activities in the region and other regions with a similar geological environment.

Journal of African Earth Sciences, Aug 1, 2021

The hilly region of Manipur especially along the NH-39 road, which is the lifeline of the State, ... more The hilly region of Manipur especially along the NH-39 road, which is the lifeline of the State, is prone to landslides every year particularly during the monsoon season. Anthropological factors, such as excessive deforestation, unsystematic changes in land use and land cover pattern and slope cultivation, etc. are indirectly initiate the process of landslides. In the present study, landslide susceptibility mapping was carried out using frequency ratio and fuzzy gamma operator models with the help of geomatics techniques. The landslide susceptibility mapping was prepared using landslide inventory data and nine landslide causative factors, i.e. lithology, land use and land cover, geomorphology, drainage density, lineament density, slope gradient, slope aspect, curvature, and elevation. These causative factors were prepared with the help of toposheet, high resolution IRS P6 LISS IV satellite imagery, cartosat DEM data and extensive field work. The landslide susceptibility maps were prepared by calculating the relationship between the landslide causative parameters with landslide areas using a frequency ratio model. To get the fuzzy membership values, the frequency ratio values were normalized between the ranges of 0 and 1. The landslide susceptibility maps were compared and prediction accuracy of both the models was derived using the area under curve (AUC) method. The success rate curves were obtained using both training and all landslide inventory dataset. For training landslide inventory dataset, the AUC value of the success rate curve for the frequency ratio model was found to be 0.8056, whereas for the fuzzy gamma operator (using c = 0.99) model, it was calculated as 0.9150. In the case of all landslide inventory dataset, the AUC value of the success rate curve for the frequency ratio model and the fuzzy gamma operator model were 0.7921 and 0.8188, respectively. The landslide susceptibility index was also compared with the landslide validation inventory dataset to obtain the prediction rate curves. The AUC value of the prediction rate curve for the frequency ratio model was 0.5681, whereas in the case of the fuzzy gamma operator model, it was 0.6721.

Momona Ethiopian Journal of Science

Leakage is one of the major problems facing the functionality and sustainability of dams. It occu... more Leakage is one of the major problems facing the functionality and sustainability of dams. It occurs through the embankment body, reservoir, foundation, and abutments. This study was conducted to identify the main causes of the leakage problem at the Dora-1 dam, located in the northern part of Ethiopia. It is an earthfill dam with a height of 43.5 m, crest length of 454 m, and reservoir capacity of 4.67 million cubic meters. Part of the embankment body was wet and swampy up to 20 m high from the ground due to leaking water. Geological investigation, laboratory test of the construction materials (including grain size analysis, specific gravity and water absorption, Atterberg limit, free swell, dispersion, permeability, and shear strength), and electrical resistivity investigation were used to identify and pinpoint the possible causes of the leakage problem. Results of the study show that the favorable geological features responsible for the occurrence of leakage include: (a) geologica...

Rainwater-Smart Agriculture in Arid and Semi-Arid Areas, 2017

In Tigray, over 78,000 dugout ponds have been constructed since 2000. The objective was to allevi... more In Tigray, over 78,000 dugout ponds have been constructed since 2000. The objective was to alleviate the problem of recurrent drought that prevails in the region every five to ten years. However, it has been reported that most of the ponds are not functional. Therefore, this paper presents an assessment of the dugout pond construction in Tigray with a particular emphasis to challenges and technical problems and pinpoints the causes that led to the poor performance of the ponds. Thus, even though rainwater harvesting ponds have the potential to ensure availability of water for various uses and generate income for smallholders, poor performance levels and insufficient impacts to local communities were widely observed in the study area due to inadequate site selection, absence of biophysical survey during design and construction, leakage and evaporation losses, and poor management of the ponds.

Hydro Nepal: Journal of Water, Energy and Environment, 2019

Construction of underground Cavern in the Himalayan region is full of challenges and uncertaintie... more Construction of underground Cavern in the Himalayan region is full of challenges and uncertainties. Experience has shown that construction in Himalayan regions requires good understanding of geology, adequate site investigations, proper design and selection of suitable construction methodology and technology. The most commonly encountered geological problems during excavation of underground structure in Hydroelectric Projects are, Fault/Thrust/Shear Zones squeezing and swelling, wedge block failure etc. Tehri Pumped Storage Plant (PSP) is located at the left bank of river Bhagirathi in the state of Uttarakhand in Northern India. This case study indicates about the geological challenges faced and their remedial measures during the construction of Tehri PSP Powerhouse Cavern having dimension of 203m x 24m x 58m.3D-geological mapping with 1:100 scales was carried out in excavated central drift of powerhouse to evaluate the rock composition, behavior of rock mass, structural features an...

Momona Ethiopian Journal of Science, 2013

Surface and groundwater chemistry being an important factor in urban planning and infrastructure ... more Surface and groundwater chemistry being an important factor in urban planning and infrastructure development, present paper tries to present the problems of corrosiveness due to groundwater chemistry in Mekelle city. Iron corrosion in distribution systems and engineering structures are common problems in many urban areas. Corrosiveness of groundwater at different localities in Mekelle and its environs has been evaluated on the basis of AAS-UV spectrophotometer-generated hydro-geochemical data. Corrosiveness of water was estimated by using corrosion indices like Larson Index, LI and Aggressive Index, AI and total dissolved solids, total carbonate hardness, chloride and sulphate data were evaluated to estimate aggressiveness of the water samples on iron pipes. Analyses of the results have shown that most of the samples from boreholes and hand dug wells compared to spring samples, are potentially aggressive. The result shows that 66.7% spring, 81.3% shallow hand dug wells and 81% borehole water samples have a Larson index (LI) above 0.5, a threshold of corrosiveness of water. This study highlights the basic characteristics of surface and groundwater chemistry and its potential hazard for corrosion of pipes, and provides a baseline information and awareness to the city planners for urban management.

Abstract: Engineering geological map of Mekele town and its environs has been established for the... more Abstract: Engineering geological map of Mekele town and its environs has been established for the first time after characterizing the geotechnical property of soils and rocks in the field and laboratory. Geological, geotechnical and engineering geological condition of Mekele area was characterized in relation to their effects to civil engineering structures. The engineering geological and geotechnical condition of the rocks and soils was studied on the bases of field description, simple in-situ geotechnical test and laboratory analysis. The dominant lithologic units are Quaternary sediment deposits (alluvial and residual soils), dolerite, sandstone, limestone-marl-shale intercalation and bedded limestone. The laboratory tests revealed that soils have medium to very high plasticity. The liquid limit of the soils varies from 50-80.8% for alluvial; 29.4-67% for residual. The dolerite shows variable engineering property in terms of strength from weak rock mass strength to very high rock...

ABSTRACT The study was conducted to assess the main causes of leakage problem in the Hashenge mic... more ABSTRACT The study was conducted to assess the main causes of leakage problem in the Hashenge micro-dam, located in the Tigray regional state, northern part of Ethiopia. The micro dam is a 19 m height earth fill dam with the length of 387 m and reservoir capacity of about 2.3 million cubic meters at maximum water level. Geological, geophysical and engineering geological investigations were conducted in the abutment and reservoir area to assess and pinpoint the main causes. The dominant lithologic units include limestone-shale-marl intercalation, dolerite and recent soil deposits. Vertical electrical sounding was used to locate geotechnical boreholes and to know vertical and lateral variability of geological materials. Geotechnical and engineering geological investigation including drilling of three boreholes and packer testing along with detail measurement and analysis of discontinuity parameters was conducted. Analysis of the data shows that the sedimentary succession, limestone-sh...

The study was conducted to assess the index properties and characterize soils and rocks of Mekele... more The study was conducted to assess the index properties and characterize soils and rocks of Mekele town located in the northern Ethiopia having an area of 45 km2. Geological, engineering geological and geotechnical condition of the rocks and soils was studied on the bases of field description, in-situ geotechnical test and laboratory analysis. Four soil types were identified in the field: clay, silt, sandy clay/silt and clayey/silty sand soils. Laboratory result revealed that moisture content of the soils ranges from 15.8 to 40.9% for clay; 21.7 to 34.7% for silt; 6.6 to 20.5% for sandy silt/clay and 14.2 to 23% for clayey/silty sand soils. pH and electrical conductivity of the soils vary from 7.1-8.5 and 180-1930μS/cm, respectively. The liquid limit (LL) in percent ranges from 29-59, 50-67.4, 37.5-70.8 and almost non-plastic to 66 for clay, silt, sandy clay/silt and clayey/silty sand, respectively. Similarly, the plasticity index in percent (PI) of the soils ranges from 14-36.6, 13....

Journal of the Geological Society of India, 2014

The hilly region of Manipur especially along the NH-39 road, which is the lifeline of the State, ... more The hilly region of Manipur especially along the NH-39 road, which is the lifeline of the State, is prone to landslides every year particularly during the monsoon season. Anthropological factors, such as excessive deforestation, unsystematic changes in land use and land cover pattern and slope cultivation, etc. are indirectly initiate the process of landslides. In the present study, landslide susceptibility mapping was carried out using frequency ratio and fuzzy gamma operator models with the help of geomatics techniques. The landslide susceptibility mapping was prepared using landslide inventory data and nine landslide causative factors, i.e. lithology, land use and land cover, geomorphology, drainage density, lineament density, slope gradient, slope aspect, curvature, and elevation. These causative factors were prepared with the help of toposheet, high resolution IRS P6 LISS IV satellite imagery, cartosat DEM data and extensive field work. The landslide susceptibility maps were prepared by calculating the relationship between the landslide causative parameters with landslide areas using a frequency ratio model. To get the fuzzy membership values, the frequency ratio values were normalized between the ranges of 0 and 1. The landslide susceptibility maps were compared and prediction accuracy of both the models was derived using the area under curve (AUC) method. The success rate curves were obtained using both training and all landslide inventory dataset. For training landslide inventory dataset, the AUC value of the success rate curve for the frequency ratio model was found to be 0.8056, whereas for the fuzzy gamma operator (using c = 0.99) model, it was calculated as 0.9150. In the case of all landslide inventory dataset, the AUC value of the success rate curve for the frequency ratio model and the fuzzy gamma operator model were 0.7921 and 0.8188, respectively. The landslide susceptibility index was also compared with the landslide validation inventory dataset to obtain the prediction rate curves. The AUC value of the prediction rate curve for the frequency ratio model was 0.5681, whereas in the case of the fuzzy gamma operator model, it was 0.6721.

Natural constraints and the damaged Meli gold mining: forecasting impact on the water resources q... more Natural constraints and the damaged Meli gold mining: forecasting impact on the water resources quality of the Meli area and the surroundings, Tigray Kaleab Adhena Abera 1, Berhane Abrha 2, Tesfamichael Gebreyohannes 2, Abdelwassie Hussien 2 , Miruts Hagos 2, Gebremedhin Berhane 2, and Kristine Walraevens 11 Laboratory for Applied Geology and Hydrogeology, Department of Geology, Ghent University, Belgium (kaleabadhena.abera@ugent.be)2 Department of Geology, School of Earth Science, Mekelle University, Ethiopia : Meli is the only modern gold mining site in the Tigray region, Northern Ethiopia. Water resources of this area and the surroundings are currently very susceptible to pollution by toxic chemicals than ever before, due to both the natural geological setup of the area and anthropogenic impacts, specifically because of the recent war in northern Ethiopia. The war that was started on November 03, 2020, resulted in the complete destruction of the mining company and tailings da...

Momona Ethiopian Journal of Science, 2021

Due to the ever-increasing demand for water in Aynalem catchment and its surrounding, there has b... more Due to the ever-increasing demand for water in Aynalem catchment and its surrounding, there has been an increased pressure on the Aynalem well field putting the sustainability of water supply from the aquifer under continuous threat. Thus, it is vital to understand the water balance of the catchment to ensure sustainable utilization of the groundwater resource. This in turn requires proper quantification of the components of water balance among which recharge estimation is the most important. This paper estimates the groundwater recharge of the Aynalem catchment using high-resolution hydro-meteorological data. Daily precipitation and temperature measurement data for years 2001-2018; groundwater level fluctuation records collected at every 30 minutes; and soil and land use maps were used to make recharge estimations. In the groundwater level fluctuation, three boreholes were monitored, but only two were utilized for the analysis because the third was under operation and does not repr...

International Journal of Earth Sciences, 2020

The Mekelle basin (area ~ 5500 km 2) is located at the immediate western margin of the Afar Depre... more The Mekelle basin (area ~ 5500 km 2) is located at the immediate western margin of the Afar Depression, which has a history of collision, subsidence, uplift, magmatism and now rifting. The evolution of such small to medium size basins as the Mekelle in a complicated geodynamic setup is a subject of debate, because several different mechanisms of basin formation could apply. To address the possible basin evolution scenarios, we combine structural and dynamic analyses of northern Ethiopia, with strong emphasis on the basin and basin bounding basement rocks. The northern basin bounding block is uplifted by about 1500 m compared with the western and southwestern basin-bounding blocks. In the basin, superposition of large-scale orthogonal brittle shear fabrics and the development of young, parallel to subparallel extensional fractures and domino faulting have produced a total of ~ 2200 m vertical displacement. These observations, coupled with the absence of gradual roll-down of the internal basin (i.e., absence of bending/folding of an elastic beam supported at both ends), imply that Mekelle basin is not an IntraCONtinental Sags (ICONS) or plate interior basin, as previously described, but is instead a multi-tectonic triggered basin. Integrated satellite images using ground-controlled measurements and deep borehole data were used to decipher the entire evolution of the basin starting from the late-collisional deformation through the regional up-doming to the sills/dikes injection and basin formation.

Bulletin of Engineering Geology and the Environment, 2020

Landslides, mainly triggered by rainfall, are one of the most common natural hazards in the north... more Landslides, mainly triggered by rainfall, are one of the most common natural hazards in the northern and central highlands of Ethiopia, resulting in the loss of human life and property. As part of the Ethiopian highlands, Mgulat Mountain (88.6 km 2) is a typical example for the occurrence of landslides and associated damages. The main aim of this research was to generate landslide susceptibility map (LSM) for the first time by considering various causative factors typical for the Mgulat Mountain area. The methods used include frequency ratio (FR) and kinematic analysis (KA) supported by GIS tools. The research involved conventional fieldwork (e.g., geological mapping, landslides inventory) and analysis and interpretation of images. From the geological mapping, major rock units were identified: quaternary deposit, basalt, red sandstone, tillite, and white sandstone. A total of 220 landslides (15.45 km 2) were identified in the study area from field survey, Google Earth and aerial photo interpretation. Five causative factors (lithology, slope steepness, distance from drainage, land use-land cover (LULC), and slope aspect) were selected based on their contribution to landslide initiation as the landslide conditioning factors for generation of the LSM. From the five causative factors, lithology and slope steepness were found to be influential as landslide conditioning factors. Specifically, lithology (red sandstone and tillite), distance to stream (0 to 300 m), LULC (bare land and settlement), and slope steepness (> 25°) have FR > 1, indicating a high relationship with landslide occurrence. Based on the generated LSM, five susceptibility classes or zones were identified (very low, low, moderate, high, and very high susceptibility). The area of each class as percentage of total area was found to be 19.53, 24.15, 22.57, 18.74, and 15.01%, for the very low to the very high class, respectively. The results of KA show potentially and marginally planar, topple, and wedge failures. The generated LSM can serve as an important tool or guide for further land-use planning and to prevent and mitigate landslide-related risks. Consequently, to consider cost-effective and technically sound mitigation measures, detailed and site-specific multidisciplinary investigations are recommended.

Environmental Earth Sciences, 2017

Overextraction of groundwater is widely occurring along the coast where good quality groundwater ... more Overextraction of groundwater is widely occurring along the coast where good quality groundwater is at risk, due to urbanization, tourist development and intensive agriculture. The Sabratah area at the northern central part of Jifarah Plain, Northwest Libya, is a typical area where the contamination of the aquifer in the form of saltwater intrusion, gypsum/anhydrite dissolution and high nitrate concentrations is very developed. Fifty groundwater samples were collected from the study area and analysed for certain parameters that indicate salinization and pollution of the aquifer. The results demonstrate high values of the parameters electrical conductivity, sodium, potassium, magnesium, chloride and sulphate which can be attributed to seawater intrusion. The intensive extraction of groundwater from the aquifer reduces freshwater outflow to the sea, creates drawdown cones and lowering of the water table to as much as 30 m below mean sea level. Irrigation with nitrogen fertilizers and domestic sewage and movement of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for the high nitrate concentration towards the south of the region. Seawater intrusion and deep salt water upconing result in general high SO 4 2concentrations in groundwater near the shoreline, where localized SO 4 2anomalies are also due to the dissolution of sebkha deposits for few wells in the nearby sebkhas. Upstream, the increase in SO 4 2concentrations in the south is ascribed to the dissolution of gypsum at depth in the upper aquifer.

Environmental Earth Sciences, 2017

The desert of eastern Libya forms one of the most arid regions of the Sahara. Libya suffers from ... more The desert of eastern Libya forms one of the most arid regions of the Sahara. Libya suffers from a shortage in water resources due to its arid climate. On the other hand, Libya has large resources of good-quality groundwater distributed in six basin systems beneath the Sahara. In order to deal with the shortage of water in most coastal cities, the Libyan government established the Great Man-Made River Project to transport millions of cubic meters of water a day from desert wellfields to the coastal cities, where over 80% of the population lives. In this paper, a hydrogeochemical study is presented for the Nubian Sandstone Aquifer in Tazerbo Wellfield, SE Libya, based on chemical analyses and physical parameters for 108 wells. Samples were collected from 108 borewells of the Nubian Aquifer (Akakus Formation) from depth range between 280 m in the north and 500 m in the south. This study is the first hydrochemical investigation in Tazerbo and also in the whole Sahara, which introduces the importance of considering the end members and the synsedimentary influence for the interpretation of the groundwater hydrochemistry. The results of the analyses indicate soft to moderately hard, lowly mineralized, slightly alkaline groundwater, with Mg 2? as the main cation and HCO 3 as the main anion. The major hydrogeochemical processes that affect the quality of water in sediments of the Nubian system at Tazerbo have been identified; the water type is mostly fresh MgHCO 3, while NaHCO 3 and KHCO 3 are also found for some wells. These water types indicate that groundwater chemistry is changed by cation exchange reactions during flushing of the aquifer by freshwater from the south.

Journal of African Earth Sciences, 2017

Highlights  Geological factors considered into account in reservoir water leakage.  Vertical el... more Highlights  Geological factors considered into account in reservoir water leakage.  Vertical electrical sounding and profiling integrated with other data for leakage zone delineation.  Discontinuities, bedding planes and regional faults play a great role in leakage problems localized in sedimentary basins.  Regional and local geology and hydrogeology have played a major role in the planning, design, construction and performance of the MDRs. Geological and geophysical investigation of water leakage from two micro-dam reservoirs: implications for future site selection, northern Ethiopia

Environmental Earth Sciences, 2016

Large increases in water demand with very little recharge have strained Libya's groundwater resou... more Large increases in water demand with very little recharge have strained Libya's groundwater resources resulting in serious declines in water levels and quality, especially along the Mediterranean coast where most of the domestic, industrial and agricultural activities are concentrated. The rapid economic expansion, coupled with sharp population growth, in the Jifarah Plain comprising Tripoli, NW-Libya, has created an immediate need for proper groundwater reserves, not only to meet the increasing population's demands, but also to secure a contingency plan. The main problem is salinization of freshwater. Based on the available hydrogeological and hydrochemical information, the sources of salinization are identified. The overpumping for groundwater contributed to the deterioration of the water quality by seawater intrusion and exposing the deep saline water. Clis the major pollutant of the aquifer. Water samples were collected from 134 sampling wells in the study area and analyzed for the major cations and anions. The chemical results for the groundwater samples in the plain are classified according to the Stuyfzand groundwater classification system. The water type is mostly CaCl, NaCl and Ca/MgMix. These water types indicate that groundwater chemistry is changed by cation exchange reactions during the mixing process between freshwater and seawater. The majority of groundwater samples (80%) show a composition that is indicative of seawater intrusion.

Environmental Earth Sciences, 2012

The study was conducted in the rapidly expanding city of Mekelle located in the northern part of ... more The study was conducted in the rapidly expanding city of Mekelle located in the northern part of Ethiopia, East Africa. An integrated approach including geomorphological, geological and engineering geological, geotechnical and hydrogeological methods were used to characterize the natural urban environment to be used as a baseline for protection and rational planning of development. Conventional field observation, test pits and drilled boreholes were used to collect soil, rock and water samples and standard laboratory procedures were applied. The results revealed that the main geologic constraints to sustainable development of the city are active erosion, instability of slopes, flood hazard, cyclic/alternating hard and weak rock layers, high swelling-shrinkage soils, shallow and unconfined groundwater with variable composition and high susceptibility to corrosion and pollution. It is recommended to avoid development and expansion of the city in areas of steep land forms, at the foot of steep slopes and in areas covered by black alluvial soil deposits. Development of a systematic multidisciplinary database aided by GIS, with continuous monitoring and updating is also highly recommended and will be useful for further refined geotechnical microzonation. It is the authors' belief that this study highlights the basic constraints and hazards the city is facing, and provides baseline information and awareness to the city planners, decision makers, geo-environmentalists, engineers and the community for future expansion and rehabilitation plans and to tackle the existing hazards.

Land Degradation & Development, 2015

Mendae Plain at Abraha Atsbaha (Tigray Region, northern Ethiopia) is an agricultural area, which ... more Mendae Plain at Abraha Atsbaha (Tigray Region, northern Ethiopia) is an agricultural area, which has been very drought-prone in the past. In the last decade, agricultural development has boosted because of the intensive use of large diameter wells that tap the phreatic aquifer. Pumped water is used for irrigation during the long dry season (October to May). Since 15 years, water harvesting measures have been implemented, mainly in the form of infiltration ponds and trenches that enhance local infiltration of rainfall runoff from hillslopes. To investigate the sustainability of the groundwater exploitation and the efficiency of the measures, the different recharge and discharge components of the water balance of data-scarce Mendae Plain have been identified and quantified, using different methods. Diffuse aquifer recharge is calculated from a soil moisture balance, based on meteorological data, and with the chloride mass balance method, based on groundwater analyses. Diffuse recharge is much higher on cultivated land plots than on non-cultivated bare soils. Rainfall infiltration in ponds and trenches is estimated based on the inflow catchment derived from the topography. Groundwater flow to a nearby river is obtained by balancing inflow and outflow by the other components over an 11 year period. The balance components are integrated into a lumped parameter model that was run for the period from 2000 to 2010. The results show that infiltration in ponds and trenches contributes between 30 and nearly 50% of total aquifer recharge, with the highest values in dry years. Changes in aquifer storage over time are an indicator for the evolution of groundwater levels in the aquifer and confirm the occurrence of two dry periods in

Journal of African Earth Sciences, 2013

Millions of people throughout the world depend on dam reservoirs for domestic water supply, irrig... more Millions of people throughout the world depend on dam reservoirs for domestic water supply, irrigation, electricity and flood protection. In the last two decades, 54 micro-dam reservoirs have been constructed in Northern Ethiopia to fight the recurrent drought and improve agricultural productivity through irrigation. However, about 60% of these micro-dam reservoirs are suffering from excessive leakage. Comprehensive studies have been carried out on two micro-dams to assess and pinpoint the causes of leakage. Arato and Hashenge micro-dams located in Northern Ethiopia have 20 m and 19 m height, and 2.59 Mm 3 and 2.23 Mm 3 reservoir capacities respectively. Observational geological description, shallow hand dug test pits, vertical electrical sounding and drilling of geotechnical holes were used to understand the overall geological, engineering geological and geo-hydrological setup of the area. The different methods applied, such as discontinuity analysis, geophysical surveys, drilling and packer tests, delivered results that were found to be in close agreement and led to the identification of the leakage zone. The geological units found in both sites are limestone-shale-marl intercalation, dolerite and recent soil deposits. The research results revealed that the limestone-shale-marl intercalation unit is heterogeneous and shows alternating sequences. Analysis of the different data shows that the limestone-shale-marl intercalation is a pervious unit (hydraulic conductivity in the range of 10 À4-10 +2 cm/s) and was found to be responsible for the excessive leakage of the micro-dams. It is hoped that the observations, data and insights gathered from these case studies will enable to plan technically and economically viable anti-leakage measures for these schemes and help for future new site selection and design activities in the region and other regions with a similar geological environment.