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Martin S. Appold - One of the best experts on this subject based on the ideXlab platform.
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The physical Hydrogeology of ore deposits
Economic Geology, 2012Co-Authors: Steven E. Ingebritsen, Martin S. AppoldAbstract:Hydrothermal ore deposits represent a convergence of fluid flow, thermal energy, and solute flux that is hydrogeologically unusual. From the hydrogeologic perspective, hydrothermal ore deposition represents a complex coupled-flow problem—sufficiently complex that physically rigorous description of the coupled thermal (T), hydraulic (H), mechanical (M), and chemical (C) processes (THMC modeling) continues to challenge our computational ability. Though research into these coupled behaviors has found only a limited subset to be quantitatively tractable, it has yielded valuable insights into the workings of hydrothermal systems in a wide range of geologic environments including sedimentary, metamorphic, and magmatic. Examples of these insights include the quantification of likely driving mechanisms, rates and paths of fluid flow, ore-mineral precipitation mechanisms, longevity of hydrothermal systems, mechanisms by which hydrothermal fluids acquire their temperature and composition, and the controlling influence of permeability and other rock properties on hydrothermal fluid behavior. In this communication we review some of the fundamental theory needed to characterize the physical Hydrogeology of hydrothermal systems and discuss how this theory has been applied in studies of Mississippi Valley-type, tabular uranium, porphyry, epithermal, and mid-ocean ridge ore-forming systems. A key limitation in the computational state-of-the-art is the inability to describe fluid flow and transport fully in the many ore systems that show evidence of repeated shear or tensional failure with associated dynamic variations in permeability. However, we discuss global-scale compilations that suggest some numerical constraints on both mean and dynamically enhanced crustal permeability. Principles of physical Hydrogeology can be powerful tools for investigating hydrothermal ore formation and are becoming increasingly accessible with ongoing advances in modeling software. * ### Notation a : total fracture aperture after dilation a : initial aperture A : cross sectional area [L2] b : thickness [L] c : specific heat capacity (usually isobaric heat capacity) [E M−1 T−1] c b : bulk compressibility of porous medium at constant fluid pressure [L t2 M−1] c s : bulk compressibility of rock matrix [L t2 M−1] c u : uniaxial compressibility of the porous medium [L t2 M−1] C : aqueous concentration [M L−3] D : hydrodynamic dispersion [L2 t−1] D w : diffusion coefficient in open water [L2 t−1] E : energy [E] F : fluxibility [M L−3 t−1] g : gravitational acceleration [L t−2] G : shear modulus, [M L−1 t−2]. H : specific enthalpy [E M−1] k : intrinsic permeability [L2] k : reference intrinsic permeability [L2] k r : relative permeability [dimensionless] K : thermal conductivity [E t−1 L−1 T−1] L : characteristic length or distance [L] M : mass [M] P : pressure [M L−1 t−2] P c : capillary pressure [M L−1 t−2] q : volumetric flow rate per unit area (volume flux, specific discharge or Darcy velocity) [L t−1] R : general source/sink term for mass, heat, or chemical reactions [variable] s s : specific storage [L−1] S : volumetric saturation [L3 L−3, dimensionless] t : time [t] T : temperature [T] u : displacement vector [L] U s : shear displacement [L] v : average linear velocity (seepage velocity) [L t−1] X : mass fraction H2O, NaCl, or CO2 in an H2O-NaCl-CO2 mixture [dimensionless] z : elevation above a datum, vertical Cartesian coordinate, or depth [L] z g : elevation parallel to the direction of gravity [L] α : dispersivity [L] α e : effective stress coefficient, [dimensionless] α T : porous medium linear thermal expansivity [T−1] β : bulk fluid compressibility [L t2 M−1] θ : potential per unit mass [E M−1] λ : coefficient of friction [dimensionless] μ : dynamic viscosity [M L−1 t−1] v : Poisson’s ratio [dimensionless] ρ : density [M L−3] σ : stress [M L−1T−2] σ eff : effective normal stress σ nref : effective normal stress to a fracture τ : tortuosity [dimensionless] φ : porosity [dimensionless] φ e : effective porosity [dimensionless] Φdil : shear dilation angle ( ∧ ) : indicates increase or decrease in a quantity (-) : indicates a nondimensionalized quantity * ### Subscripts f : refers to the fluid mixture in place (either a single phase or a two-phase mixture) l : refers to liquid m : refers to the porous medium r : refers to the rock v : refers to vapor (steam) : refers to an initial state
D A Hughes - One of the best experts on this subject based on the ideXlab platform.
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satellite earth observation as a tool to conceptualize hydrogeological fluxes in the sandveld south africa
Hydrogeology Journal, 2013Co-Authors: Zahn Műnch, Julian Conrad, Lesley Gibson, Anthony R Palmer, D A HughesAbstract:In semi-arid, groundwater-dependent regions of South Africa, allocation of additional water resources can become problematic in the absence of quantified regional groundwater recharge values. In this study in the northern Sandveld, remote-sensing-data products for precipitation (P) and evapotranspiration (ET) are used to quantify groundwater recharge and guide the conceptualization of the Hydrogeology of the study area. Data from three ET models (ETMODIS, MOD16, Pitman rainfall-runoff) are compared; these models concur best in years of average rainfall, with model results deviating up to 30 % in wet years. The MODIS data product (MOD16) is used in conjunction with gridded precipitation data to calculate spatial regional recharge. The long-term precipitation minus evapotranspiration (P–ET) budget closes on a positive 13 ± 25 %; however, when correcting ET (20 % underestimation determined using the chloride mass balance method), the catchment average potential recharge is reduced to −4 ± 30 %. The use of P–ET clearly identifies potential recharge zones at higher elevation and discharge zones, highlighting irrigated agriculture. The usefulness of identifying recharge zones is demonstrated in the value added to conceptualizing the Hydrogeology. Since some uncertainty around the accuracy of ET data still remains, it is recommended that the MODIS data product be validated more comprehensively in semi-arid environments.
Steven E. Ingebritsen - One of the best experts on this subject based on the ideXlab platform.
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The physical Hydrogeology of ore deposits
Economic Geology, 2012Co-Authors: Steven E. Ingebritsen, Martin S. AppoldAbstract:Hydrothermal ore deposits represent a convergence of fluid flow, thermal energy, and solute flux that is hydrogeologically unusual. From the hydrogeologic perspective, hydrothermal ore deposition represents a complex coupled-flow problem—sufficiently complex that physically rigorous description of the coupled thermal (T), hydraulic (H), mechanical (M), and chemical (C) processes (THMC modeling) continues to challenge our computational ability. Though research into these coupled behaviors has found only a limited subset to be quantitatively tractable, it has yielded valuable insights into the workings of hydrothermal systems in a wide range of geologic environments including sedimentary, metamorphic, and magmatic. Examples of these insights include the quantification of likely driving mechanisms, rates and paths of fluid flow, ore-mineral precipitation mechanisms, longevity of hydrothermal systems, mechanisms by which hydrothermal fluids acquire their temperature and composition, and the controlling influence of permeability and other rock properties on hydrothermal fluid behavior. In this communication we review some of the fundamental theory needed to characterize the physical Hydrogeology of hydrothermal systems and discuss how this theory has been applied in studies of Mississippi Valley-type, tabular uranium, porphyry, epithermal, and mid-ocean ridge ore-forming systems. A key limitation in the computational state-of-the-art is the inability to describe fluid flow and transport fully in the many ore systems that show evidence of repeated shear or tensional failure with associated dynamic variations in permeability. However, we discuss global-scale compilations that suggest some numerical constraints on both mean and dynamically enhanced crustal permeability. Principles of physical Hydrogeology can be powerful tools for investigating hydrothermal ore formation and are becoming increasingly accessible with ongoing advances in modeling software. * ### Notation a : total fracture aperture after dilation a : initial aperture A : cross sectional area [L2] b : thickness [L] c : specific heat capacity (usually isobaric heat capacity) [E M−1 T−1] c b : bulk compressibility of porous medium at constant fluid pressure [L t2 M−1] c s : bulk compressibility of rock matrix [L t2 M−1] c u : uniaxial compressibility of the porous medium [L t2 M−1] C : aqueous concentration [M L−3] D : hydrodynamic dispersion [L2 t−1] D w : diffusion coefficient in open water [L2 t−1] E : energy [E] F : fluxibility [M L−3 t−1] g : gravitational acceleration [L t−2] G : shear modulus, [M L−1 t−2]. H : specific enthalpy [E M−1] k : intrinsic permeability [L2] k : reference intrinsic permeability [L2] k r : relative permeability [dimensionless] K : thermal conductivity [E t−1 L−1 T−1] L : characteristic length or distance [L] M : mass [M] P : pressure [M L−1 t−2] P c : capillary pressure [M L−1 t−2] q : volumetric flow rate per unit area (volume flux, specific discharge or Darcy velocity) [L t−1] R : general source/sink term for mass, heat, or chemical reactions [variable] s s : specific storage [L−1] S : volumetric saturation [L3 L−3, dimensionless] t : time [t] T : temperature [T] u : displacement vector [L] U s : shear displacement [L] v : average linear velocity (seepage velocity) [L t−1] X : mass fraction H2O, NaCl, or CO2 in an H2O-NaCl-CO2 mixture [dimensionless] z : elevation above a datum, vertical Cartesian coordinate, or depth [L] z g : elevation parallel to the direction of gravity [L] α : dispersivity [L] α e : effective stress coefficient, [dimensionless] α T : porous medium linear thermal expansivity [T−1] β : bulk fluid compressibility [L t2 M−1] θ : potential per unit mass [E M−1] λ : coefficient of friction [dimensionless] μ : dynamic viscosity [M L−1 t−1] v : Poisson’s ratio [dimensionless] ρ : density [M L−3] σ : stress [M L−1T−2] σ eff : effective normal stress σ nref : effective normal stress to a fracture τ : tortuosity [dimensionless] φ : porosity [dimensionless] φ e : effective porosity [dimensionless] Φdil : shear dilation angle ( ∧ ) : indicates increase or decrease in a quantity (-) : indicates a nondimensionalized quantity * ### Subscripts f : refers to the fluid mixture in place (either a single phase or a two-phase mixture) l : refers to liquid m : refers to the porous medium r : refers to the rock v : refers to vapor (steam) : refers to an initial state
Herman Bouwer - One of the best experts on this subject based on the ideXlab platform.
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artificial recharge of groundwater Hydrogeology and engineering
Hydrogeology Journal, 2002Co-Authors: Herman BouwerAbstract:Artificial recharge of groundwater is achieved by putting surface water in basins, furrows, ditches, or other facilities where it infiltrates into the soil and moves downward to recharge aquifers. Artificial recharge is increasingly used for short- or long-term underground storage, where it has several advantages over surface storage, and in water reuse. Artificial recharge requires permeable surface soils. Where these are not available, trenches or shafts in the unsaturated zone can be used, or water can be directly injected into aquifers through wells. To design a system for artificial recharge of groundwater, infiltration rates of the soil must be determined and the unsaturated zone between land surface and the aquifer must be checked for adequate permeability and absence of polluted areas. The aquifer should be sufficiently transmissive to avoid excessive buildup of groundwater mounds. Knowledge of these conditions requires field investigations and, if no fatal flaws are detected, test basins to predict system performance. Water-quality issues must be evaluated, especially with respect to formation of clogging layers on basin bottoms or other infiltration surfaces, and to geochemical reactions in the aquifer. Clogging layers are managed by desilting or other pretreatment of the water, and by remedial techniques in the infiltration system, such as drying, scraping, disking, ripping, or other tillage. Recharge wells should be pumped periodically to backwash clogging layers. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s10040-001-0182-4.
Timothy Moss - One of the best experts on this subject based on the ideXlab platform.
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Pasts and Presents of Urban Socio-Hydrogeology: Groundwater Levels in Berlin, 1870–2020
'MDPI AG', 2021Co-Authors: Theresa Frommen, Timothy MossAbstract:Although it is self-evident that today’s groundwater issues have a history that frames both problems and responses, these histories have received scant attention in the socio-hydrogeological literature to date. This paper aims to enrich the field of socio-Hydrogeology with a novel, historical perspective on groundwater management whilst simultaneously demonstrating the value to water history of engaging with groundwater. This is achieved by applying hydrogeological, socio-hydrogeological, and historical methods in an interdisciplinary and collaborative research process while analysing a case study of urban groundwater management over a 150-year period. In the German capital Berlin, local aquifers have always been central to its water supply and, being close to the surface, have made for intricate interactions between urban development and groundwater levels. The paper describes oscillations in groundwater levels across Berlin’s turbulent history and the meanings attached to them. It demonstrates the value to socio-Hydrogeology of viewing the history of groundwater through a socio-material lens and to urban history of paying greater attention to subsurface water resources. The invisibility and inscrutability associated with groundwater should not discourage attention, but rather incite curiosity into this underexplored realm of the subterranean city, inspiring scholars and practitioners well beyond the confines of Hydrogeology
