scholarly journals Hydrogeological conceptual model of andesitic watersheds revealed by high-resolution geophysics

2019 ◽  
Author(s):  
Benoit Vittecoq ◽  
Pierre-Alexandre Reninger ◽  
Frédéric Lacquement ◽  
Guillaume Martelet ◽  
Sophie Violette
Keyword(s):  
Hydraulic Conductivity ◽  
Conceptual Model ◽  
Subduction Zones ◽  
Preferential Flow ◽  
Watershed Scale ◽  
Volcanic Island ◽  
Hydrogeological Characteristics ◽  
Volcanic Islands ◽  
Very High ◽  
Vertical Variability

Abstract. We conducted a multidisciplinary study at the watershed scale of an andesitic-type volcanic island in order to better characterize the hydrogeological functioning of aquifers and to better evaluate groundwater resource. A helicopter-borne TDEM survey was conducted in 2013 over Martinique Island in order to investigate underground volcanic structures and lithology, characterized by high lateral and vertical variability, and resulting in a very high heterogeneity of their hydrogeological characteristics. Correlations were made on three adjacent watersheds between resistivity data along flight lines and geological and hydrogeological data from 51 boreholes and 24 springs, showing that the younger the formations, the higher their resistivity. Correlation between resistivity, geology and transmissivity data of three aquifers is attested: the older the formation, the lower its resistivity, and the higher its transmissivity. Moreover, we demonstrate that the main geological structures lead to preferential flow circulations and that hydrogeological watershed can differ from topographical watershed. The consequence is that even if the topographical watershed is small, underground flow circulations can add significant amount of water to river watershed’s water balance. This effect is amplified when lava domes and their roots are situated upstream, as they present very high hydraulic conductivity leading to deep preferential groundwater flow circulations. We also reveal, unlike basaltic-type volcanic islands, that hydraulic conductivity increases with age in this andesitic-type volcanic island. This trend is interpreted as the consequence of tectonic fracturing associated to earthquakes in subduction zones associated to andesitic volcanic islands. Finally, our approach allows characterizing in detail the hydrogeological functioning and identifying the properties of the main aquifer and aquitard units, leading to the proposition of a hydrogeological conceptual model at the watershed scale. This working scale seems particularly suitable due to the complexity of edifices, with heterogeneous geological formations presenting high lateral and vertical variability. Moreover, our study offers new guidelines for accurate correlations between resistivity, geology and hydraulic conductivity for volcanic islands. Finally, our results will also help stakeholders toward a better management of water resource.

scholarly journals Hydrogeological conceptual model of andesitic watersheds revealed by high-resolution heliborne geophysics

2019 ◽  
Vol 23 (5) ◽  
pp. 2321-2338 ◽  
Author(s):  
Benoit Vittecoq ◽  
Pierre-Alexandre Reninger ◽  
Frédéric Lacquement ◽  
Guillaume Martelet ◽  
Sophie Violette
Keyword(s):  
Hydraulic Conductivity ◽  
Conceptual Model ◽  
Preferential Flow ◽  
Groundwater Resources ◽  
Watershed Scale ◽  
Volcanic Island ◽  
Multidisciplinary Study ◽  
Hydrogeological Characteristics ◽  
Volcanic Islands ◽  
Very High

Abstract. We conducted a multidisciplinary study at the watershed scale of an andesitic-type volcanic island in order to better characterize the hydrogeological functioning of aquifers and to better evaluate groundwater resources. A heliborne Time Domain ElectroMagnetic (TDEM) survey was conducted over Martinique in order to investigate underground volcanic structures and lithology, characterized by high lateral and vertical geological variability and resulting in a very high heterogeneity of their hydrogeological characteristics. Correlations were made on three adjacent watersheds between resistivity data along flight lines and geological and hydrogeological data from 51 boreholes and 24 springs, showing that the younger the formations, the higher their resistivity. Correlation between resistivity, geology and transmissivity data of three aquifers is attested: within the interval 10–100 ohm m and within a range of 1 to 5.5 Ma, the older the formation, the lower its resistivity, and the older the formation, the higher its transmissivity. Moreover, we demonstrate that the main geological structures lead to preferential flow circulations and that hydrogeological watersheds can differ from topographical watersheds. The consequence is that, even if the topographical watershed is small, underground flows from an adjacent watershed can add significant amounts of water to such a catchment. This effect is amplified when lava domes and their roots are situated upstream, as they present very high hydraulic conductivity leading to deep preferential groundwater flow circulations. We also reveal, unlike basaltic-type volcanic islands, that hydraulic conductivity increases with age in this andesitic-type volcanic island. This trend is interpreted as the consequence of tectonic fracturing associated with earthquakes in this subduction zone, related to andesitic volcanic islands. Finally, our approach allows characterization in detail of the hydrogeological functioning and identification of the properties of the main aquifer and aquitard units, leading to the proposition of a hydrogeological conceptual model at the watershed scale. This working scale seems particularly suitable due to the complexity of edifices, with heterogeneous geological formations presenting high lateral and vertical variability. Moreover, our study offers new guidelines for accurate correlations between resistivity, geology and hydraulic conductivity for volcanic islands. Finally, our results will also help stakeholders toward a better management of water resources.

scholarly journals Modeling Rasmussen’s dynamic modeling problem: drift towards a boundary of safety

2021 ◽  
Author(s):  
J. Bradley Morrison ◽  
Robert L. Wears
Keyword(s):  
High Risk ◽  
Conceptual Model ◽  
Performance Improvement ◽  
Dynamic Modeling ◽  
System Dynamics Model ◽  
Dynamics Model ◽  
System Safety ◽  
Simulation Experiments ◽  
Scenarios Simulation ◽  
Very High

AbstractWe build a system dynamics model based on a conceptual model originally proposed by safety scientist Jens Rasmussen to explore the dynamics of a safety system subject to pressures for performance improvement. Rasmussen described forces that generate a drift in the boundary of acceptable performance that can push the organization towards “flirting with the margin” and thus operate at very high risk of catastrophic safety failure. Simulations of the model faithfully replicate the behavior described by Rasmussen and others in a variety of scenarios. Simulation experiments further illuminate the potential for risky behavior and point towards some approaches to better system safety.

Upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale in deeply weathered crystalline aquifers

2012 ◽  
Vol 416-417 ◽  
pp. 83-97 ◽  
Author(s):  
B. Dewandel ◽  
J.C. Maréchal ◽  
O. Bour ◽  
B. Ladouche ◽  
S. Ahmed ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Effective Porosity ◽  
Watershed Scale

scholarly journals Quantitative estimations of aquifer properties from resistivity in the Bolivian highlands

2019 ◽  
Vol 2 (1) ◽  
pp. 113-124
Author(s):  
Etzar Gómez ◽  
Viktor Broman ◽  
Torleif Dahlin ◽  
Gerhard Barmen ◽  
Jan-Erik Rosberg
Keyword(s):  
Hydraulic Conductivity ◽  
Saline Water ◽  
Cost Effective ◽  
Unconsolidated Sediments ◽  
Aquifer System ◽  
Transient Electromagnetic ◽  
Rock Formations ◽  
Hydrogeological Characteristics ◽  
Electrical Soundings ◽  
Available Information

Abstract Resistivity data constitute the largest part of the available information to assess the hydrogeological characteristics of the aquifer system near Oruro, in the central part of the Bolivian Altiplano. Two aquifers are part of this system; top unconsolidated sediments storing fresh water in their granular voids, overlying fractured hard rock formations where saline water was detected in connection to some faults. This study proposes an indirect and cost-effective way to estimate aquifer hydraulic properties for the groundwater management in the region. Hydraulic conductivity and transmissivity in the top aquifer were estimated using an empirical linear relationship between hydraulic conductivity and resistivity. This latter parameter, as well as the aquifer thickness, were obtained from the inverted models corresponding to the geoelectrical tests performed in the study area (electrical resistivity tomography, transient electromagnetic soundings and vertical electrical soundings). The highest estimated transmissivity values are ∼4.0 × 10−2 m2/s located in the centre of the study area, the lowest values are ∼3.4 × 10−3 m2/s, located around thermal intrusions to the south and where the top of the bedrock is shallow (∼20 m depth) to the west. The methodology presented in this study makes wider use of resistivity measurements to identify promising groundwater production sites.

Identifying Covariates to Assess the Spatial Variability of Saturated Soil Hydraulic Conductivity Using Robust Cokriging at the Watershed Scale

2020 ◽  
Vol 20 (3) ◽  
pp. 1491-1502 ◽  
Author(s):  
Mauricio Fornalski Soares ◽  
Luana Nunes Centeno ◽  
Luís Carlos Timm ◽  
Carlos Rogério Mello ◽  
Douglas Rodrigo Kaiser ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Spatial Variability ◽  
Saturated Soil ◽  
Watershed Scale ◽  
Soil Hydraulic Conductivity ◽  
Soil Hydraulic

scholarly journals Insights into the late-Sixties taxocenosis of Oniscidea from the Pontine islands (West Mediterranean) (Peracarida: Isopoda)

2019 ◽  
Vol 51 (2) ◽  
pp. 217-223
Author(s):  
Gabriele Gentile ◽  
Roberto Argano ◽  
Stefano Taiti
Keyword(s):  
Research Program ◽  
Environmental Conditions ◽  
Small Island ◽  
National Council ◽  
Tyrrhenian Sea ◽  
Number Of Species ◽  
Pontine Islands ◽  
Volcanic Islands ◽  
Very High

We report and discuss faunistic data of Oniscidea inhabiting the Pontine islands, a group of five small volcanic islands and several islets in the Tyrrhenian Sea, located about 60 km from the Italian mainland. Data here presented were primarily obtained from the examination of the material collected during a three-year (1965-1968) research program supported by the Italian National Council of Research and aimed at investigating Mediterranean small island faunas, including Oniscidea. Despite the sampling was not specifically directed at Oniscidea, these data may provide insights into the structure of the Oniscidean taxocenosis of the islands as it existed fifty years ago. Thirty-five species belonging to 11 families, 8 ecological and 7 biogeographical classes were found on these islands. Such number of species of Oniscidea is very high, if we consider the low number of islands and their small sizes. Changes in climate and environmental conditions occurred in the last fifty years would call for a new investigation.

Identification of preferential flow effects on hydraulic conductivity measurements using a fluorescent tracer

2000 ◽  
Vol 37 (2) ◽  
pp. 479-484
Author(s):  
Tom A Al ◽  
David W Blowes
Keyword(s):  
Hydraulic Conductivity ◽  
Measurement Errors ◽  
Preferential Flow ◽  
Conductivity Measurements ◽  
Fine Grained ◽  
The Core ◽  
Core Samples ◽  
Dye Tracer ◽  
Order Of Magnitude ◽  
Constant Head

Core samples were collected from fractured and unfractured zones within fine-grained, unconsolidated mine tailings. The hydraulic conductivity of the core samples was measured in a constant-head permeameter. A fluorescent dye tracer was added to the constant-head reservoir in the permeameter. The tests were run for approximately 48 h, then the cores were sectioned to observe the distribution of dye. Flow through the fractures results in hydraulic conductivity measurements up to one order of magnitude greater than that of unfractured tailings. Observations of the dye distribution in samples following permeameter measurements are used to identify cases where preferential flow in fractures has influenced the hydraulic conductivity measurements. The dye tracer distribution also indicates where measurement errors may be suspected due to flow leakage around the core sample.Key words: tracers, hydraulic conductivity, fractures, tailings.

Effect of plastic fragments on hydraulic characteristics of pretreated municipal solid waste

2006 ◽  
Vol 43 (12) ◽  
pp. 1333-1343 ◽  
Author(s):  
Mingliang Xie ◽  
Dirk Aldenkortt ◽  
Jean-Frank Wagner ◽  
Gerhard Rettenberger
Keyword(s):  
Fluid Flow ◽  
Hydraulic Conductivity ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Conceptual Model ◽  
Hydraulic Properties ◽  
Thin Sheet ◽  
Biological Pretreatment ◽  
Soil Material

A systematic study was undertaken of the granular composition and hydraulic properties of municipal solid waste (MSW) produced by mechanical–biological pretreatment (MBP–MSW) from three different treatment plants with the aim of evaluating the potential application of MBP–MSW as an alternative barrier material for landfill final cover systems. Despite its coarse granular composition, MBP–MSW has low hydraulic conductivity. Long-term permeability tests show that the hydraulic conductivity decreases with time. The most likely explanation for the long-term changes in permeability is the swelling of organic material contained within the compost. In the case of saturated flow, the virtually impermeable plastic fragments embedded in the material impede fluid flow. In the unsaturated case, such fragments slow down the drying process by disrupting fluid flow and allowing pooling of water above horizontally oriented fragments. The larger the number and size of the plastic fragments, the greater the influence on hydraulic conductivity and shrinkage. These processes can be better understood with the newly developed conceptual model, the thin-sheet model. Based on this conceptual model, laboratory tests were undertaken to compare natural soil material with mixtures of soil material and plastic fragments. Corresponding numerical simulations of some experiments verified the influence of plastic fragments on the hydraulic properties of MBP–MSW.Key words: mechanical–biological pretreatment, municipal solid waste (MSW), thin-sheet model, plastic fragment, hydraulic conductivity, drying test.

scholarly journals Accelerated gravity testing of aquitard core permeability and implications at formation and regional scale

2015 ◽  
Vol 12 (3) ◽  
pp. 2799-2841
Author(s):  
W. A. Timms ◽  
R. Crane ◽  
D. J. Anderson ◽  
S. Bouzalakos ◽  
M. Whelan ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Preferential Flow ◽  
Fluid Velocity ◽  
Regional Scale ◽  
Geotechnical Centrifuge ◽  
Regional Flow ◽  
Clayey Silt ◽  
Vertical Hydraulic Conductivity ◽  
Core Permeability

Abstract. Evaluating the possibility of leakage through low permeability geological strata is critically important for sustainable water supplies, the extraction of fuels from strata such as coal beds, and the confinement of waste within the earth. The current work demonstrates that relatively rapid and reliable hydraulic conductivity (K) measurement of aquitard cores using accelerated gravity can inform and constrain larger scale assessments of hydraulic connectivity. Steady state fluid velocity through a low K porous sample is linearly related to accelerated gravity (g-level) in a centrifuge permeameter (CP) unless consolidation or geochemical reactions occur. The CP module was custom designed to fit a standard 2 m diameter geotechnical centrifuge (550 g maximum) with a capacity for sample dimensions of 30 to 100 mm diameter and 30 to 200 mm in length, and a maximum total stress of ~2 MPa at the base of the core. Formation fluids were used as influent to limit any shrink–swell phenomena which may alter the permeability. Vertical hydraulic conductivity (Kv) results from CP testing of cores from three sites within the same regional clayey silt formation varied (10−7 to 10−9 m s−1, n = 14). Results at one of these sites (1.1 × 10−10 to 3.5 × 10−9 m s−1, n = 5) that were obtained in < 24 h were similar to in situ Kv values (3 × 10−9 m s−1) from pore pressure responses over several weeks within a 30 m clayey sequence. Core scale and in situ Kv results were compared with vertical connectivity within a regional flow model, and considered in the context of heterogeneity and preferential flow paths at site and formation scale. More reliable assessments of leakage and solute transport though aquitards over multi-decadal timescales can be achieved by accelerated core testing together with advanced geostatistical and numerical methods.

scholarly journals Hydrogeological settings of a volcanic island (San Cristóbal, Galapagos) from joint interpretation of airborne electromagnetics and geomorphological observations

2012 ◽  
Vol 9 (8) ◽  
pp. 9661-9686 ◽  
Author(s):  
A. Pryet ◽  
N. d'Ozouville ◽  
S. Violette ◽  
B. Deffontaines ◽  
E. Auken
Keyword(s):  
Resistivity Structure ◽  
Volcanic Island ◽  
Transient Electromagnetic ◽  
Geophysical Surveys ◽  
Joint Interpretation ◽  
Volcanic Islands ◽  
Definition Of ◽  
Optimum Management ◽  
Perched Aquifers ◽  
Airborne Electromagnetics

Abstract. Many volcanic islands face freshwater stress and the situation may worsen with climate change and sea level rise. In this context, an optimum management of freshwater resources becomes crucial, but is often impeded by the lack of data. With the aim of investigating the hydrogeological settings of Southern San Cristóbal Island (Galapagos), we conducted an helicopter-borne, transient electromagnetic survey with the SkyTEM system. It provided unprecedented insights in the 3-D resistivity structure of this extinct basaltic shield. Combined with remote sensing and fieldwork, it allowed the definition of the first hydrogeological conceptual model of the island. Springs are fed by a series of perched aquifers overlying a regional basal aquifer subject to seawater intrusion. Dykes, evidenced by alignments of eruptive cones at the surface, correspond to sharp sub-vertical contrasts in resistivity in the subsurface, and impound groundwater in a summit channel. Combined with geomorphological observations, airborne electromagnetics is shown to be a useful tool for hydrogeological exploratory studies in complex, poorly known environments. It allows optimal development of land-based geophysical surveys and drilling campaigns.

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