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While these written contributions are valuable, the real mother lode of Hubbert lore comes from a series of face-to-face interviews carried out over nine multihour sessions in Bethesda, Maryland, by the science historian Ronald E. Doel in 1989, just before Hubbert's sudden death later that year. Hubbert replied that his conclusion that Muskat's expression for Darcy's law is physically erroneous "cannot be invalidated by the insertion of escape clauses to the effect that gravity is being neglected" (Hubbert [20]). After his foray into groundwater science, Hubbert went on to make paradigm-shifting contributions in several other subfields of geology, notably his explanation of the hydrodynamic entrapment of petroleum (Hubbert [18]), his study of the mechanisms of hydraulic fracturing (Hubbert and Willis [16]), and his solution to the longstanding mysteries around the mechanisms of overthrust faulting (Hubbert and Rubey [15]). In his review, Hubbert pillories Muskat for not correcting the pressure-based version of Darcy's law, despite "the twelve years which have elapsed" between the two books, and sarcastically suggests that this incorrect form "should hereafter be known as 'Muskat's law'" (Hubbert [19]). [Extracted from the article]

This map clearly outlines the Chalk outcrops (unit 16 in Figure 3) of the London Basin overlain by London Clay (unit 17) and greatly facilitated the subsequent development of this major aquifer for the London water supply. His geological map of Britain, Figure 3, published in 1815 (Winchester 2001), now rests in the Natural History Museum in London and he is rightly known as the Father of British Geology. First Use of Hydrogeology in Modern Context Joseph Lucas (1846-1926) is credited with first use of the term hydrogeology in its modern context. Appearance of Hydrogeology Jean-Baptiste Lamarck (1744-1829) the eminent French scientist had an early interest in geology that was subsequently completely overshadowed by his contributions to the science of biology. [Extracted from the article]

Numerous continuous conduits exist in rock masses. These conduits affect the specific discharge distribution of the bulk rock mass. In this study, a modified theoretical model is presented to explore the specific discharge distribution in bedrock with an axisymmetric infilled conduit. The movement of fluid in the free region abides by the Navier‐Stokes equation, and the seepage flow in the filling and rock regions complies with the Brinkman‐extended Darcy equation. The analytical solution for the specific discharge distribution is derived by requiring flow continuity at the domain interface. This solution can be reduced to Darcy's law and Poiseuille's law. Sensitivity analysis shows that both the relative aperture of the free region and the permeability of the filling or rock regions positively influence the specific discharge. The specific discharge distribution curves seem to have an intersection for different porosity values. Moreover, the width of the transition layer where the porous media flow differs from traditional Darcy's flow is positively correlated with the permeability. However, the width is not directly correlated with the relative aperture and the porosity. Article impact statement: Assessing the specific discharge of groundwater flow in jointed rocks or karst aquifers. [ABSTRACT FROM AUTHOR]

Gustave Dumont, a mining engineer, reported to the City Council of Liège (Belgium), on a feasibility study for a large drinking water production project based on galleries in an unconfined chalk aquifer. GLO:GWT/01sep21:gwat13123-fig-0004.jpg PHOTO (COLOR): 4 One of the "lateral" galleries in the Cretaceous chalk of Hesbaye still in use for the water supply of the City of Liège by the Public Water Company of the Liège area ("Compagnie Intercommunale des Eaux de Liège" CILE). Acknowledgments The authors thank Luc Demoulin (City of Liège, Ulysse Capitaine Library) for the digitized maps of Gustave Dumont's report and Damien Pirlot de Corbion for the Gustave Dumont's bust picture and for helping them to locate the bust. Although the galleries were never practically implemented, it is astonishing how this work on the hydrogeology of the Chalk aquifer appears similar (at least for the lithology, the recommended methods and the way of describing the hydrogeological conditions) to what was described in earlier work of Gustave Dumont (see below) for Liège in 1856. [Extracted from the article]

The article discusses the importance of understanding the travel time of groundwater and the movement of contaminants through aquifers. It suggests the use of a new term, "transportivity," to describe the combined influence of porosity and saturated thickness on travel time calculations. The article also explores the relationship between transportivity and the mean residence time of discharging water in groundwater systems. It concludes by drawing an analogy between transmissivity and transportivity, highlighting their fundamental properties in aquifers. [Extracted from the article]

The journey of water and how it interacts with the geological environments through which it flows is a fundamental aspect of hydrogeology. It provides a unique and immersive perspective of this fascinating karst landscape and helps the audience to visualize and understand the hydrogeological and scientific concept of rapid infiltration of groundwater into the subsurface of these soluble rocks. The Burren karst landscape in County Clare is an ideal setting for the film's exploration of the inception horizon. [Extracted from the article]

The authors convey their concerns about the boundary condition (BC) nomenclature confusion in groundwater flow modeling. Topics mentioned include translation of general BC formulae into standard groundwater flow BCs through application of Darcy's Law, the concept of specified-head condition, and the influence of surface water bodies within groundwater models.

Numerical modeling of groundwater‐surface water interactions provides vital information necessary for determining the extent of nutrient transport, quantifying water budgets, and delineating zones of ecological support. The hydrologic data that drive these models are often collected at disparate scales and subsequently incorporated into numerical models through upscaling techniques such as piecewise constancy or geostatistical methods. However, these techniques either use basic interpolation methods, which often simplifies the system of interest, or utilize complex statistical methods that are computationally expensive, time consuming, and generate complex subsurface configurations. We propose a bulk parameter termed "vertically integrated hydraulic conductivity" (KV), and defined as the depth‐integrated resistance to fluid flow sensed at the groundwater‐surface water interface, as an alternative to hydraulic conductivity when investigating vertical fluxes across the groundwater‐surface water interface. This bulk parameter replaces complex subsurface configurations in situations dominated by vertical fluxes and where heterogeneity is not of primary importance. To demonstrate the utility of KV, we extracted synthetic temperature time series data from a forward numerical model under a variety of scenarios and used those data to quantify vertical fluxes using the amplitude ratio method. These quantified vertical fluxes and the applied hydraulic head gradient were subsequently input into Darcy's Law and used to quantify KV. This KV was then directly compared to the equivalent hydraulic conductivity (KT) assuming an infinitely extending layer. Vertically integrated hydraulic conductivity allows for more accurate and robust flow modeling across the groundwater‐surface water interface in instances where complex heterogeneities are not of primary concern. Article impact statement: We present a new bulk parameter to represent the depth‐integrated resistance to flow across the groundwater‐surface water interface. [ABSTRACT FROM AUTHOR]

The article discusses a study that introduces a method to measure vertical hydraulic conductivity (Kv) via gravity flow that can be done in the field or laboratory using freshly collected saturated core samples. Highlights include testing of Hv with the cylinder in any orientation, schematic equipment setup and parameters used to calculate Kv from gravity drainage tests, and cumulative flow volume versus time and other parameters used to calculate Kv from gravity drainage tests.

This technical note describes an effective and inexpensive field technique for measuring the saturated hydraulic conductivity of both undisturbed cores and repacked soil samples. The method requires no specialized equipment; everything that is required can be obtained in a hardware store. The method is a straightforward field implementation of the widely used falling-head laboratory analysis directly derived from Darcy's law. As such, it sidesteps the need for empirical assumptions about soil texture and the relationship between saturated and unsaturated flow components which many permeameter-based methods rely upon. The method is shown to produce results that are consistent with K values obtained elsewhere in the same homogeneous sand formation. Furthermore, the proposed method is useful for measuring hydraulic conductivity in drill cuttings obtained from direct push or auguring drill techniques, which cannot be done with any other field method. The range of hydraulic conductivity values that this test is appropriate for is on the order of 1E − 7 m/s to 1E − 3 m/s. [ABSTRACT FROM AUTHOR]

Grady uses a sand tank model to demonstrate the effects of hydrostatic pressure, uplift pressure, and groundwater flow on structures. If the video had begun traditionally with a description of groundwater flow paths around a dam, Grady would likely lose the attention of the viewer. Oftentimes in short YouTube videos, the math and physics behind natural phenomena are overlooked in the interest of keeping the video approachable for all audiences. [Extracted from the article]

The recent release of MODFLOW-USG, which allows model grids to have irregular, unstructured connections, requires a modification of the particle-tracking algorithm used by MODPATH. This paper describes a modification of the semi-analytical particle-tracking algorithm used by MODPATH that allows it to be extended to rectangular-based unstructured grids by dividing grid cells with multi-cell face connections into sub-cells. The new method will be incorporated in the next version of MODPATH which is currently under development. [ABSTRACT FROM AUTHOR]

Heat transfer due to groundwater flow can significantly affect closed geothermal systems. Here, a screening method is developed, based on Peclet numbers for these systems and Darcy's law. Conduction-only conditions should not be expected where specific discharges exceed 10−8 m/s. Constraints on hydraulic gradients allow for preliminary screening for advection based on rock or soil types. Identification of materials with very low hydraulic conductivity, such as shale and intact igneous and metamorphic rock, allow for analysis with considering conduction only. Variability in known hydraulic conductivity allows for the possibility of advection in most other rocks and soil types. Further screening relies on refinement of estimates of hydraulic gradients and hydraulic conductivity through site investigations and modeling until the presence or absence of conduction can be confirmed. [ABSTRACT FROM AUTHOR]

We introduce a simple correction to coastal heads for constant-density groundwater flow models that contain a coastal boundary, based on previous analytical solutions for interface flow. The results demonstrate that accurate discharge to the sea in confined aquifers can be obtained by direct application of Darcy's law (for constant-density flow) if the coastal heads are corrected to (( α + 1)/ α) h s − B/2 α, in which hs is the mean sea level above the aquifer base, B is the aquifer thickness, and α is the density factor. For unconfined aquifers, the coastal head should be assigned the value [ABSTRACT FROM AUTHOR]

Small-scale hyporheic zone ( HZ) models often use a spatial periodic boundary ( SPB) pair to simulate an infinite repetition of bedforms. SPB's are common features of commercially available multiphysics modeling packages. MODFLOW's lack of this boundary type has precluded it from being effectively utilized in this area of HZ research. We present a method to implement the SPB in MODFLOW by development of the appropriate block-centered finite-difference expressions. The implementation is analogous to MODFLOW's general head boundary package. The difference is that the terms on the right hand side of the solution equations must be updated with each iteration. Consequently, models that implement the SPB converge best with solvers that perform both inner and outer iterations. The correct functioning of the SPB condition in MODFLOW is verified by two examples. This boundary condition allows users to build HZ-bedform models in MODFLOW, facilitating further research using related codes such as MT3DMS and PHT3D. [ABSTRACT FROM AUTHOR]

Also included is content not typically found in hydrogeology textbooks (e.g., oil-shale fracking, 3-D predictive modeling, groundwater rebound), which gives readers a well-rounded perspective on current and emerging concepts within the field. A course on hydrogeology is usually reserved for upper-level geology or engineering students and emphasizes the quantitative aspects of the discipline. The last chapter discusses the history of hydrogeology, the responsibilities of a hydrogeologist, and the interdisciplinary progression of hydrogeology in the future. [Extracted from the article]

The article examines the advances in hydrogeology between the middle of the 19th and 20th century particularly on the geological basis for preferential groundwater flow in bedrock aquifers. It refers to Henry Darcy's law for laminar flow in porous media and the Darcy-Weisbach equation for turbulent flow in pipes. Moreover, the concept of bedrock flow in overburden aquifers should be assessed differently in contrast to the water-table laws as it is not intended for general application.

The stability of subsurface Light Nonaqueous Phase Liquids (LNAPLs) is a key factor driving expectations for remedial measures at LNAPL sites. The conventional approach to resolving LNAPL stability has been to apply Darcy's Equation. This paper explores an alternative approach wherein single-well tracer dilution tests with intermittent mixing are used to resolve LNAPL stability. As a first step, an implicit solution for single-well intermittent mixing tracer dilution tests is derived. This includes key assumptions and limits on the allowable time between intermittent mixing events. Second, single-well tracer dilution tests with intermittent mixing are conducted under conditions of known LNAPL flux. This includes a laboratory sand tank study and two field tests at active LNAPL recovery wells. Results from the sand tank studies indicate that LNAPL fluxes in wells can be transformed into formation fluxes using corrections for (1) LNAPL thicknesses in the well and formation and (2) convergence of flow to the well. Using the apparent convergence factor from the sand tank experiment, the average error between the known and measured LNAPL fluxes is 4%. Results from the field studies show nearly identical known and measured LNAPL fluxes at one well. At the second well the measured fluxes appear to exceed the known value by a factor of two. Agreement between the known and measured LNAPL fluxes, within a factor of two, indicates that single-well tracer dilution tests with intermittent mixing can be a viable means of resolving LNAPL stability. [ABSTRACT FROM AUTHOR]

A model function relating effective stress to fracture permeability is developed from Hooke's law, implemented in the tensorial form of Darcy's law, and used to evaluate discharge rates and pressure distributions at regional scales. The model takes into account elastic and statistical fracture parameters, and is able to simulate real stress-dependent permeabilities from laboratory to field studies. This modeling approach gains in phenomenology in comparison to the classical ones because the permeability tensors may vary in both strength and principal directions according to effective stresses. Moreover this method allows evaluation of the fracture porosity changes, which are then translated into consolidation of the medium. [ABSTRACT FROM AUTHOR]

Comment by Xu-Sheng Wang; Comment by Shlomo P. Neuman; Comment by Otto D. L. Strack; Comment by Arnold Verruijt, Mirmosadegh Jamali, Brian Seymour; Comment by Jacob Bear, Alexander H.-D. Cheng; Authors' reply by Chongxi Chen, Xingxing Kuang and Jiu Jimmy Jiao [ABSTRACT FROM AUTHOR]

Hydraulically and statistically based methods were analyzed to identify the most reliable method to predict spring flows in a karst aquifer. Measured water levels at nearby observation wells, measured spring pool altitudes, and the distance between observation wells and the spring pool were the parameters used to match measured spring flows. Measured spring flows at six Upper Floridan aquifer springs in central Florida were used to assess the reliability of these methods to predict spring flows. Hydraulically based methods involved the application of the Theis, Hantush-Jacob, and Darcy-Weisbach equations, whereas the statistically based methods were the multiple linear regressions and the technology of artificial neural networks (ANNs). Root mean square errors between measured and predicted spring flows using the Darcy-Weisbach method ranged between 5% and 15% of the measured flows, lower than the 7% to 27% range for the Theis or Hantush-Jacob methods. Flows at all springs were estimated to be turbulent based on the Reynolds number derived from the Darcy-Weisbach equation for conduit flow. The multiple linear regression and the Darcy-Weisbach methods had similar spring flow prediction capabilities. The ANNs provided the lowest residuals between measured and predicted spring flows, ranging from 1.6% to 5.3% of the measured flows. The model prediction efficiency criteria also indicated that the ANNs were the most accurate method predicting spring flows in a karst aquifer. [ABSTRACT FROM AUTHOR]

The article focuses on the studies regarding the hydrogeology of carbonate aquifers. It highlights the approaches that have been used in the study in which one focuses on data from wells using Darcy's law and the other focuses on data from springs and caves using the Darcy-Weisbach equation for the interpretation of flow through the major conduits in the aquifer. It views the connection between landforms and ground water in karst regions. It indicates the work of J. Cvijić that has presented modern ideas in karst geomorphology as well as the karst ground water system with three hydrographic zones.

The article offers information on the development of the MODFLOW-2005 conduit flow process (CFP) by the U.S. Geological Survey (USGS). The MODFLOW-2005 CFP has been used in the implementation of the non-Darcian, dual-permeability flow regimes which have not been considered in traditional codes of water flow based on Darcy's law. The performance of the tool's code has been evaluated through benchmark tests, application of CFP to a test site, and comparison between CFP and the Carbonate Aquifer Void Evolution (CAVE). The code has been described as easy to use and presents parameters that need collecting field data not taken for traditional laminar, equivalent continuum groundwater flow models.

In a historic 6-3 decision, the U.S. Supreme Court (SCOTUS) ruled in April 2020 that some groundwater is now regulated under the Clean Water Act (CWA) and a National Pollutant Discharge and Elimination System (NPDES) permit is required when it can be demonstrated there is a "functional equivalent" of a direct discharge of a pollutant from a point source into navigable waters via groundwater. The pertinent question is, when is a discharge of groundwater containing pollutants from a point source "functionally equivalent" to a NPDES direct discharge into navigable waters? SCOTUS apparently has left it to the groundwater community to provide a scientific basis for evaluating functionally equivalent NPDES discharges. [Extracted from the article]

The use of hydraulic head measurements in ground water of variable density is considerably more complicated than for the case of constant-density ground water. A theoretical framework for dealing with these complications does exist in the current literature but suffers from a lack of awareness among many hydrogeologists. When corrections for density variations are ignored or not properly taken into account, misinterpretation of both ground water flow direction and magnitude may result. This paper summarizes the existing theoretical framework and provides practical guidelines for the interpretation of head measurements in variable-density ground water systems. It will be argued that, provided that the proper corrections are taken into account, fresh water heads can be used to analyze both horizontal and vertical flow components. To avoid potential confusion, it is recommended that the use of the so-called environmental water head, which was initially introduced to facilitate the analysis of vertical ground water flow, be abandoned in favor of properly computed fresh water head analyses. The presented methodology provides a framework for determining quantitatively when variable-density effects on ground water flow need to be taken into account or can be justifiably neglected. Therefore, we recommend that it should become part of all hydrogeologic analyses in which density effects are suspected to play a role. [ABSTRACT FROM AUTHOR]

During the design of a natural gradient tracer experiment, it was noticed that the hydraulic gradient was too small to measure reliably on an ∼500-m2 site. Additional wells were installed to increase the monitored area to 26,500 m2, and wells were instrumented with pressure transducers. The resulting monitoring system was capable of measuring heads with a precision of ±1.3 × 10−2 m. This measurement error was incorporated into Monte Carlo calculations, in which only hydraulic head values were varied between realizations. The standard deviation in the estimated gradient and the flow direction angle from the x-axis (east direction) were calculated. The data yielded an average hydraulic gradient of 4.5 × 10−4±25% with a flow direction of 56° southeast ±18°, with the variations representing 1 standard deviation. Further Monte Carlo calculations investigated the effects of number of wells, aspect ratio of the monitored area, and the size of the monitored area on the previously mentioned uncertainties. The exercise showed that monitored areas must exceed a size determined by the magnitude of the measurement error if meaningful gradient estimates and flow directions are to be obtained. The aspect ratio of the monitored zone should be as close to 1 as possible, although departures as great as 0.5 to 2 did not degrade the quality of the data unduly. Numbers of wells beyond three to five provided little advantage. These conclusions were supported for the general case with a preliminary theoretical analysis. [ABSTRACT FROM AUTHOR]

Borehole dilution techniques use repeated fluid column profiling after establishment of an initial uniform condition to monitor the rate at which ambient ground water moves into a borehole. Application of the dilution technique in a monitoring well makes it possible to estimate the horizontal Darcy flow velocity of ground water in the aquifer surrounding the borehole. Previous investigators have demonstrated the technique using either relatively concentrated saline solutions or deionized water to produce a fluid column with properties distinctly different from those of local ground water. We present a new dilution technique using the food color Brilliant Blue FCF (Euro code E-133) to mark the fluid column and using a specially constructed photometric sensor to characterize the dilution of this dye over time. The effective application of this technique is documented by two practical examples. [ABSTRACT FROM AUTHOR]

There are ∼470,000 km2 of karst aquifers that feed many large springs in North China. Turbulent flow often exists in these karst aquifers, which means that the classical ground water model based on Darcy’s law cannot be applied here. Ground water data are rare for these aquifers. As a consequence, it is difficult to quantitatively investigate ground water flow in these karst systems. The purpose of this study is to develop a parsimonious model that predicts karst spring discharge using gray system theory. In this theory, a white color denotes a system that is completely characterized and a black color represents a system that is totally unknown. A gray system thus describes a complex system whose characteristics are only partially known or known with uncertainty. Using this theory, we investigated the karst spring discharge time series over different time scales. First, we identified three specific components of spring discharge: the long-term trend, periodic variation, and random fluctuation. We then used the gray system model to simulate the long-term trend and obtain periodic variation and random fluctuation components. Subsequently, we developed a predictive model for karst spring discharge. Application of the model to Liulin Springs, a representative example of karst springs in northern China, shows that the model performs well. The predicted results suggest that the Liulin Springs discharge will likely decrease over time, with small fluctuations. [ABSTRACT FROM AUTHOR]

According to common understanding, the advective velocity of a conservative solute equals the average linear pore-water velocity. Yet direct monitoring indicates that the two velocities may be different in heterogeneous media. For example, at the Camp Dodge, Iowa, site the advective velocity of discrete C1- plumes was less than one tenth of the average pore-water velocity calculated from Darcy's law using the measured hydraulic gradient, effective porosity, and hydraulic conductivity (K) from large-scale three-dimensional (3D) techniques, e.g., pumping tests. Possibly, this difference reflects the influence of different pore systems, if the K relevant to transient solute flux is influenced more by lower-K heterogeneity than a steady or quasi-steady water flux. To test this idea, tracer tests were conducted under controlled laboratory conditions. Under one-dimensional flow conditions, the advective velocity of discrete conservative solutes equaled the average pore-water velocity determined from volumetric flow rates and Darcy's law. In a larger 3D flow system, however, the same solutes migrated at ∼65% of the average pore-water velocity. These results, coupled with direct observation of dye tracers and their velocities as they migrated through both homogeneous and heterogeneous sections of the same model, demonstrate that heterogeneity can slow the advective velocity of discrete solute plumes relative to the average pore-water velocity within heterogeneous 3D flow sytems. [ABSTRACT FROM AUTHOR]

Fresh ground water entering an estuary can be mixed with salt water in the upper few decimeters of the sediment. As a result, net measured discharge rates at the sediment-water interface can be equal to the volume discharge of fresh ground water, although the salinity of the escaping water is high. Benthic chambers, vented to a collection bag, were used to measure specific volume discharge rates over 5 cm/day near the shoreline of a wide, shallow lagoon—Great South Bay, New York—situated at the surface of a coastal plain aquifer. These rates decreased to 1.5 cm/day at a distance of 100 m from shore. Although the flow rate is expected to be inversely correlated to the tidal water level elevation, and has been shown to be so modulated at other sites, no consistent variation in discharge with tidal phase was found; the tidal range (25 cm) may have been too small to have a measurable effect. Water collected at a particular location freshened over time from 30 to 23 ppt in 12 hours. Piezometers recorded vertical hydraulic gradients (at ambient salinity) between 0.08 and 0.02 in the upper meter of the sediment and the vertical hydraulic conductivity was measured by a falling head test to be between 1 and 20 m/day. The discharge rates calculated by Darcy's law decreased offshore from dozens of cm/day within 10 m of shore to 1.8 cm/day at a distance of 100 m, consistent with measured seepage rates. Conductivity measurements imply that pore water salinity decreases from ambient bay values at the sea floor to near fresh water values at a depth of 0.6 m into the sediment. The vertical downward dispersion coefficient for salt was estimated to be 0.02 m2/day. This could be due to the superposition of water wave-induced dispersion in the sediment with gravitational convection (salt fingering). [ABSTRACT FROM AUTHOR]

Darcy flow equations relating vertical and bedding-parallel flow to vertical and bedding-parallel gradient components are derived for a skewed Cartesian grid in a vertical plane, correcting for structural dip given the principal hydraulic conductivities in bedding-parallel and bedding-orthogonal directions. Incorrect-minus-correct flow error results are presented for ranges of structural dip (0 ≤ Θ ≤ 90) and gradient directions (0 ≤ φ ≤ 360). The equations can be coded into ground water models (e.g., MODFLOW) that can use a skewed Cartesian coordinate system to simulate flow in structural terrain with deformed bedding planes. Models modified with these equations will require input arrays of strike and dip, and a solver that can handle off-diagonal hydraulic conductivity terms. [ABSTRACT FROM AUTHOR]

Presents a study which described governing equations for fluid recovery processes in a monitoring well. Information on light nonaqueous phase liquids; Analysis of bail-down tests based on volumetric equilibrium and multiphase Darcy flow assumptions; Interpretation of results; Conclusions.

Discusses the calculation of travel time estimates for contaminant fronts or plumes using estimates of average pore velocities from Darcy's law calculations. Mathematical development; Description of the travel time equations for arbitrary concentration; Use of travel time estimates among hydrogeologists.

Introduces the analytical solution for Darcian means, from Darcy's law, for the case of an exponential relative conductivity relation and one possible approximation for general use, a piecewise Brooks-Corey Darcian mean. Brief review of Darcian means; Darcian mean of the exponential form; Conclusions.

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I much appreciate the Comment of Dr. Szyma'nski on my editorial and agree with him that Dupuit-Forchheimer (D-F) models are traditionally seen as models in which vertical flow is ignored. In 1952 Polubarinova-Kochina presented a brief analysis to approximate vertical flow in an unconfined D-F model resulting from the curvature of the phreatic surface (Polubarinova-Kochina [5], 408 to 409). I That i explains why Kirkham's D-F model works and why approximate 3D streamlines in a D-F model compare so favorably with those obtained from fully 3D solutions. [Extracted from the article]

The average pore velocity of ground water according to Darcy’s law is a function of the fluid pressure gradient and the gravitational force (per unit volume of ground water) and of aquifer properties. There is also an acceleration exerted on ground water that arises from the Earth’s rotation. The magnitude and direction of this rotation-induced force are determined in exact mathematical form in this article. It is calculated that the gravitational force is at least 300 times larger than the largest rotation-induced force anywhere on Earth, the latter force being maximal along the equator and approximately equal to 34 N/m3 there. This compares with a gravitational force of ∼104 N/m3. [ABSTRACT FROM AUTHOR]

Presents a discussion of the study 'Coefficient Permeability Determined by Measurable Parameters,' by D.W. Barr which deals with the concept of Darcy's Law in hydraulic conductivity, published in the May-June 2001 issue of the periodical 'Groundwater.' Notation on hydraulic conductivity; Comparison of variables.

The authors reflect on the different terms used to describe the q symbol in the Darcy's law formula q=-K dh/ds, including Darcy velocity, Darcy flux and groundwater flux, which they find confusing and misleading. They state that they thoroughly examine an article or report every time they encounter the term "Darcy velocity" to find out what is truly meant. They also discuss the reasons why such terms matter in the study of groundwater hydrology.

Discusses the connection between contours in ground water hydrology and Darcy's law. Darcy's law in mathematical form; Procedure for contouring.