scholarly journals Contribution of Sentinel Radar Images 1Ato the Extraction of Lineaments from the Lobo Watershed (Center-West of the Ivory Coast)

2020 ◽  
pp. 11-25
Author(s):  
J. O. K. Kouadio ◽  
B. Dibi ◽  
M. J. Mangoua ◽  
A. B. Konan- Waidhet ◽  
B. Kamagaté
Keyword(s):  
Average Length ◽  
Fracture Network ◽  
High Yield ◽  
Aquifer System ◽  
Underground Waters ◽  
Radar Images ◽  
Run Off ◽  
Density Maps ◽  
Climatic Hazards ◽  
Bedrock Aquifer

The improvement of the conditions of access to drinking water for the populations of the Lobo watershed requires the exploitation of groundwater because of the surface water which remains exposed to climatic hazards and the impacts of anthropic activities. And yet, these underground waters finds himself bedrock aquifer which are complex aquifers. Thus, the objective of this study is to characterize those fissure aquifers that who govern underground run-off in the aquifer system of the Lobo catchment area. The methodology adopted consisted in using 1A sentinel radar images to map fractures and their spatial distribution. The validation of the lineaments first consisted in comparing and highlighting the lineaments from the radar images and the fractures revealed from photo-geological images. Next, we superimposed the map of lineaments on the map of boreholes with a flow rate greater than or equal to 5 m3/h, which were considered as productive boreholes. To determine the traffic corridors, this fracturing map was superimposed on the piezometric map. This work made it possible to extract 9,753 lineaments over a surface area of 7,000 km². The various validation techniques enabled us to confirm 121 major fractures with an average length of 9 km. In addition, the most productive boreholes are located on average less than 300 m from the fractures. The analysis of the distribution of the orientations of these fractures revealed a heterogeneity of direction and a predominance of the N-S; NW-SE and NE-SW families. The Fracturing density maps and density of the number of fracture crossing points highlight the spatial heterogeneity of the fracture network which is controlled by geomorphology, geological formations and lithological contacts. The river Lobo and its main tributary the Dé, flow preferentially in fractures. This river and its tributary drains the aquifer system. The results obtained from different thematic maps are useful for the realisation of future high-yield hydraulic wells (Q ≥ 5 m3/h).

Multi-scale hydrogeologic characterization of a leaky till–mantled fractured bedrock aquifer system

2015 ◽  
Vol 52 (12) ◽  
pp. 1945-1955 ◽  
Author(s):  
William G. Lukas ◽  
Don J. DeGroot ◽  
David W. Ostendorf ◽  
Erich S. Hinlein
Keyword(s):  
Hydraulic Conductivity ◽  
Coarse Grained ◽  
Small Scale ◽  
Data Sets ◽  
Aquifer System ◽  
Monitoring Wells ◽  
Fractured Bedrock ◽  
Decadal Scale ◽  
Fractured Bedrock Aquifer ◽  
Bedrock Aquifer

The paper presents hydrogeologic properties for a leaky till–mantled fractured bedrock aquifer system based on geophysical and hydraulic tests performed at a drumlin located in northeastern Massachusetts, USA. The site profile consists of a fractured bedrock aquifer overlain by a 30 m thick unweathered, coarse-grained till aquitard. Steady state, decadal scale, hydraulics varied little until seasonal irrigation pumping was initiated in recent years, causing a substantial annual drawdown in the aquifer and leakage from the overlying till. High frequency hydraulic head data sets collected in monitoring wells record the hydraulic response to the irrigation pumping. These data sets, together with results from small scale slug and purge tests performed in monitoring wells, are used to characterize the hydrogeologic behavior of this groundwater system. Geophysical logging performed in bedrock wells confirmed the presence of numerous flowing fractures. The large-scale continuum analysis of the fractured bedrock aquifer response to the irrigation pumping yields transmissivity values consistent with those determined from the small-scale, short-term purge test results. The low hydraulic conductivity till has a significant impact on the drawdown behavior of the fractured bedrock aquifer. Calibrated values from the collective data sets and analyses result in the following properties for the 30 m thick unweathered till: hydraulic conductivity K′ = 7.2 × 10−9 m/s, transmissivity T′ = 2.3 × 10−8 m2/s, and storativity S′ = 2.7 × 10−4, and for the underlying fractured bedrock aquifer: T = 6.5 × 10−6 m2/s with an average fracture aperture of 46 μm and hydraulic conductivity Kf = 1.3 × 10−3 m/s. These results should describe similar unweathered coarse-grained till–mantled fractured bedrock aquifer systems and provide useful data for preliminary analyses prior to any site-specific investigations.

scholarly journals Occurrence, Geochemistry and Speciation of Elevated Arsenic Concentrations in a Fractured Bedrock Aquifer System

2021 ◽  
Vol 81 (3) ◽  
pp. 414-437
Author(s):  
Ellen McGrory ◽  
Tiernan Henry ◽  
Peter Conroy ◽  
Liam Morrison
Keyword(s):  
Solid Phase ◽  
Groundwater Resources ◽  
Arsenic Speciation ◽  
Aquifer System ◽  
Fractured Bedrock ◽  
North Eastern ◽  
Eastern Usa ◽  
Major Controlling Factor ◽  
Geologic Setting ◽  
Bedrock Aquifer

AbstractThe presence of elevated arsenic concentrations (≥ 10 µg L−1) in groundwaters has been widely reported in areas of South-East Asia with recent studies showing its detection in fractured bedrock aquifers is occurring mainly in regions of north-eastern USA. However, data within Europe remain limited; therefore, the objective of this work was to understand the geochemical mobilisation mechanism of arsenic in this geologic setting using a study site in Ireland as a case study. Physicochemical (pH, Eh, d-O2), trace metals, major ion and arsenic speciation samples were collected and analysed using a variety of field and laboratory-based techniques and evaluated using statistical analysis. Groundwaters containing elevated dissolved arsenic concentrations (up to 73.95 µg L−1) were characterised as oxic-alkali groundwaters with the co-occurrence of other oxyanions (including Mo, Se, Sb and U), low dissolved concentrations of Fe and Mn, and low Na/Ca ratios indicated that arsenic was mobilised through alkali desorption of Fe oxyhydroxides. Arsenic speciation using a solid-phase extraction methodology (n = 20) showed that the dominant species of arsenic was arsenate, with pH being a major controlling factor. The expected source of arsenic is sulphide minerals within fractures of the bedrock aquifer with transportation of arsenic and other oxyanion forming elements facilitated by secondary Fe mineral phases. However, the presence of methylarsenical compounds detected in groundwaters illustrates that microbially mediated mobilisation processes may also be (co)-occurring. This study gives insight into the geochemistry of arsenic mobilisation that can be used to further guide research needs in this area for the protection of groundwater resources.

scholarly journals Occurrence, Geochemistry and Speciation of Elevated Arsenic Concentrations in a Fractured Bedrock Aquifer System

2021 ◽  
Author(s):  
Ellen McGrory ◽  
Tiernan Henry ◽  
Peter Conroy ◽  
Liam Morrison
Keyword(s):  
Solid Phase ◽  
Arsenic Speciation ◽  
Eastern United States ◽  
Aquifer System ◽  
Fractured Bedrock ◽  
North Eastern ◽  
Major Controlling Factor ◽  
Fe Oxyhydroxides ◽  
Geologic Setting ◽  
Bedrock Aquifer

Abstract The presence of elevated arsenic concentrations (≥10 µg L-1) in groundwaters has been widely reported in areas of south east Asia with recent studies showing its detection in fractured bedrock aquifers mainly in regions of north-eastern United States. Data within Europe remains limited; therefore, the objective of this work was to understand the geochemical mobilisation mechanism of arsenic in this geologic setting. Physiochemical (pH, Eh, d-O2), trace metals, major ion and arsenic speciation samples were collected and analysed using a variety of field and laboratory-based techniques and evaluated using statistical analysis including multivariate analysis. Elevated dissolved arsenic concentrations (up to 73.95 µg L-1) were observed in oxic-alkali groundwaters with the co-occurrence of other oxyanions (e.g. Mo, Se, Sb and U), low dissolved concentrations of Fe and Mn and low Na/Ca ratios indicating that arsenic was mobilised through alkali desorption of Fe oxyhydroxides. Arsenic speciation using a solid-phase extraction methodology (n=20) showed that the dominant species of arsenic present in groundwater was arsenate, with pH being a major controlling factor. The expected source of arsenic is sulfide minerals within fractures of the bedrock aquifer with transportation of arsenic and other oxyanion-forming elements facilitated by secondary Fe mineral phases. However, the presence of methylarsenical compounds detected in the groundwaters illustrates that microbially mediated mobilisation processes were also (co)-occurring. This study demonstrates how field speciation of arsenic can be utilised to overcome analytical limitations of conventional laboratory speciation and to facilitate in the interpretation of the environmental mobility of arsenic within groundwaters.

scholarly journals Relation of surface and underground waters in Chungará and Cotacotani lake districts, northern Chile: an isotopic study

2010 ◽  
Vol 33 (2) ◽  
pp. 299 ◽  
Author(s):  
Christian Herrera ◽  
Juan Jose Pueyo ◽  
Alberto Saez ◽  
Blas L. Valero-Garces
Keyword(s):  
Isotopic Composition ◽  
Chloride Content ◽  
Debris Avalanche ◽  
Isotopic Study ◽  
Aquifer System ◽  
River Waters ◽  
Underground Waters ◽  
Lumped Parameter ◽  
Chilean Altiplano ◽  
Δ18o And Δd

Lake Chungará and Cotacotani lake districts are surface water bodies located to the northwest of Lauca Basin in the northern Chilean Altiplano. Surface and underground waters show low to moderate saline content and an electrical conductivity in the range of 48.7 to 3090 μS/cm. The lakes are related to a system of aquifers on the nearby volcano flanks and debris avalanche deposits of Parinacota volcano. On the basis of δ18O and δD isotopic composition and its correlation with the chloride content in Chungará and Cotacotani lake, spring, and Chungará river waters it is demonstrated that: a. Lake Chungará's waters show vertical and horizontal homogeneous isotopic composition, which indicates a good mixture of waters in the lake; b. an important part of the Cotacotani lake recharge feeding come from Lake Chungará, that flows laterally as groundwater; c. the groundwater that feeds the springs of the area has its main recharge in the spring-summer (October-March) precipitation. The high content of tritium (3H) measured in spring waters of the area suggested a very recent recharge (last decades) of the aquifer system. The application of lumped parameter models to interpret the water residence time in the aquifer indicates that the piston flow model shows the best fit to the isotopic composition of Chungará-Cotacotani groundwater.

Synthesis and Characterization of Mesoporous Multi-Walled Carbon Nanotubes at Low Frequencies Electromagnetic Waves

2013 ◽  
Vol 26 ◽  
pp. 117-122 ◽  
Author(s):  
Hasan Soleimani ◽  
Noorhana Yahya ◽  
Noor Rasyada Ahmad Latiff ◽  
Krzysztof Koziol ◽  
B.M. Maciejewska ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electromagnetic Waves ◽  
Average Length ◽  
Textural Properties ◽  
Lattice Defects ◽  
Bet Surface Area ◽  
High Yield ◽  
Tem Analysis ◽  
Low Frequencies ◽  
Microwave Absorbing Materials

For electromagnetic absorbing and shielding applications, carbon nanotubes (CNT) are widely used due to their excellent electrical and physical properties. Fabrication of microwave absorbing materials involves the use of compounds capable of generating dielectric and/or magnetic losses when impinged by an electromagnetic wave. The presence of lattice defects e.g. vacancies and dislocations contributes to the loss and attenuation in the electromagnetic waves, which in turn remarkably enhance the absorption ability of the material. With the CVD technique which is known to produce several lattice defects in the final product, aligned MWCNTs were successfully synthesized by pyrolizing toluene and ferrocene in an inert argon environment. The morphology analysis of the aligned MWCNTs was conducted via FESEM and TEM analysis, to reveal the average length of approximately 295 μm, with diameters in the range of 60-200 nm. EDS analysis indicates the high yield of CNTs, with more than 90% in weight composition, with less than 5 % Fe impurities presence. Textural properties of MWCNTs were studied by measuring pore size and BET surface area. To understand the response of CNTs to an electromagnetic field, permeability and permittivity measurement were conducted in the frequency range of 100 Hz to 110 MHz. In conclusion, the presence of defects in MWCNTs is desirable for enhanced electromagnetic absorption ability.

scholarly journals Field, Laboratory and Modeling Evidence for Strong Attenuation of a Cr(VI) Plume in a Mudstone Aquifer Due to Matrix Diffusion and Reaction Processes

Soil Systems ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 18
Author(s):  
Steven Chapman ◽  
Beth Parker ◽  
Tom Al ◽  
Richard Wilkin ◽  
Diana Cutt ◽  
...  
Keyword(s):  
Reactive Transport ◽  
Fracture Network ◽  
Matrix Diffusion ◽  
Rock Matrix ◽  
Laboratory Methods ◽  
Field Laboratory ◽  
Bedrock Aquifer ◽  
Reaction Processes ◽  
Low Solubility

This study uses a combination of conventional and high resolution field and laboratory methods to investigate processes causing attenuation of a hexavalent chromium (Cr(VI)) plume in sedimentary bedrock at a former industrial facility. Groundwater plume Cr(VI) concentrations decline by more than three orders of magnitude over a 900 m distance down gradient from the site. Internal plume concentrations generally exhibit stable to declining trends due to diffusive and reactive transport in the low permeability matrix as fluxes from the contamination source dissipate due to natural depletion processes and active remediation efforts. The strong attenuation is attributed to diffusion from mobile groundwater in fractures to immobile porewater in the rock matrix, and reactions causing transformation of aqueous Cr(VI) to low-solubility Cr(III) precipitates, confirmed by high spatial resolution rock matrix contaminant concentrations and comparisons with groundwater concentrations from multi-level sampling within the plume. Field characterization data for the fracture network and matrix properties were used to inform 2-D discrete-fracture matrix (DFM) numerical model simulations that quantify attenuation due to diffusion and reaction processes, which show consistency with field datasets, and provide insights regarding future plume conditions. The combination of field, laboratory and modeling evidence demonstrates effects of matrix diffusion and reaction processes causing strong attenuation of a Cr(VI) plume in a sedimentary bedrock aquifer. This approach has important implications for characterization of sites with Cr(VI) contamination for improved site conceptual models and remediation decision-making.

Palaeodrainage at Uluru-Kata Tjuta National Park and implications for water resources.

1998 ◽  
Vol 20 (2) ◽  
pp. 255 ◽  
Author(s):  
P English
Keyword(s):  
Water Resources ◽  
Water Conservation ◽  
National Park ◽  
Gamma Ray ◽  
Aquifer System ◽  
The North ◽  
Groundwater Aquifer ◽  
Run Off ◽  
Elevation Model ◽  
Landscape Units

The stakeholders in the atypical rangeland area of Uluyu-Kata Tjufa National Park in the Northern Territory are the Aboriginal owners, hundreds of thousands of tourists, and vulnerable desert wildlife species. Sustainable water resources and maintenance of the integrity of the unique geological, ecological and cultural environment at Uluyu are major issues being addressed by the trustees of the Park. The Dune Plains area between Uluyu (Ayers Rock) and Kata Tjula (the Olgas) is the setting for a deep palaeovalley. The flat, dune-covered landscape of the present-day Dune Plains area provides no indication of the existence of the underlying palaeovalley. Integrated datasets including aeromagnetic and airborne gamma-ray spectrometric imagery, processed Landsat Thematic Mapper imagery, a digital elevation model, and water-bore logs, have enabled reconstruction of the Dune Plains palaeoriver valley. The datasets reveal a heterogeneous basement topography of domes and basins with 100 m of vertical relief (a buried 'mini-Kata Tjuia') at depth beneath the Dune Plains area, between the rock monoliths. The ancient valley became completely infilled with lake, river and wind-borne sediments during the Tertiary and Quaternary. Major faults traversing the basement beneath the area influenced early erosion and valley initiation. The palaeovalley was originally a closed valley which later evolved to a through-flowing river that fed Lake Amadeus to the north. The Dune Plains palaeovalley is now the setting for a compound bedrock- Cainozoic-sediment aquifer system which is the major source of water supply for the inhabitants and tourists of Uluyu-Kata Tjufa National Park. Major landscape units making up the Uluyu area include groundwater calcrete, sheetwash slopes of red earth, sandplains and dunefields, and modern ephemeral alluvial braidplains that are constrained to corridors afforded by swale networks. The sheetwash unit forms gently sloping aprons around outcrops and supports banded mulga shrubland. During rainfall, surface run-off acts as a 'sheetflow recharge mechanism'. This mechanism maximises water conservation allowing survival of the mulga groves and associated ecosystems. During major rainfall events, the sheetflow processes augment replenishment of the aquifer system at the base of the slopes. The palaeodrainage configuration and hydrodynamics of both the surface environment and the subsurface aquifer system are complex. The methodology used to reconstruct the Dune Plains palaeodrainage and associated aquifer system, and the hydrodynamic processes described for the Uluru area are applicable to widespread rangeland areas elsewhere across the continent. Keywords: Uluyu, Kata Tjula, Dune Plains, palaeovalley, palaeodrainage, hydrology, groundwater, aquifer, sheetwash, red earths, calcrete, hydrodynamics, mulga (Acacia aneura), run-off, run-on, recharge.

Sign in / Sign up

Export Citation Format

Share Document