ALBERT

Notes: The paper presents a straightforward method of calculating approximate orientation parameters (six degrees of freedom) of a known targeted object relative to a single calibrated camera. These can then initialise an optimised non-linear calculation of the same parameter values. The method uses the mathematics of a scaled parallel projection and is particularly suited to narrow angle images obtained using a telescope, telephoto or zoom lens. However, the method can also be used with cameras having wider fields of view provided the target group occupies a moderately small part of the image.

Notes: This paper describes three mathematical modelling methods for high-resolution declassified CORONA KH-4B images. Since CORONA images are collected with a panoramic camera, several types of geometric distortions are involved. Two methods use the modified collinearity equations, and the third involves the terrain-dependent rational function model (RFM) which is considered to be a generic sensor model. Comparative analysis of the three mathematical modelling methods is undertaken. The results show that a ± 1·5 pixels level of horizontal and vertical accuracy can be obtained. A digital elevation model (DEM) of a test site is also created.

Notes: Digital photogrammetry and softcopy workstations have added a new dimension to aerial triangulation, and some of the previously manual procedures are now available in automated form. Also, commercial software packages for automatic aerial triangulation came on to the market in the last decade. In this study, the results of automatic aerial triangulation using four triangulation software packages, Z/I Imaging's MATCH-AT (ISMAT) and ISAT, LH Systems’ MST and VirtuoZo AAT, are presented. For the comparison of the results of the tie point extraction and the bundle block adjustment for triangulation, a sub-block from the Uster block in Switzerland was selected and used. Differences between these software packages are discussed with respect to their functionality and performance in detail. The achieved standard deviation of image coordinates varies between 0·2 and 0·5 pixel for the systems tested. The more signalised control points and check points to be used, the better the σ0 estimate which could be expected. The average number of extracted tie points varied from system to system with respect to the matching method and the resolution of the images used in the programs. The digital aerial triangulation of the Uster sub-block was faster than analytical triangulation and the elapsed time for triangulation of one image using different systems varies between about 0·5 and 6 min. Nevertheless, results also show that automated aerial triangulation is still prone to error in all systems. Image matching produces many blunders, which can only be handled efficiently by using a sophisticated blunder detection procedure, as is available with robust estimation. This is not the case for all the systems tested, however. There still remains a lot to be done in terms of development (improvement of matching, for example, by integrating robust estimation for error detection at an early stage, implementation of on-line triangulation, better internal quality control procedures, more transparent and simple user interfaces and more useful information for the user with better software manuals). However, it was shown that automatic aerial triangulation provides higher redundancy and reliability of results and much more economical photogrammetric practice than ever before.

Notes: The Photogrammetric Society was formed in 1952. The Council of the Society considered that the twentieth anniversary was a good point at which to record the events which led to its formation and the significant occasions and decisions which have taken place since 1952. Consequently, Paul Lamboit was invited to compile this History. He has placed the birth and development of the Society within the national and international photogrammetric context and his record of the deliberations which took place between 1947 and 1952 will be of particular interest to historians of our subject.This account was first published in a limited edition in 1971. Sufficient interest has since been expressed to prompt a wider circulation through publication in the Photogrammetric Record.The author served the Society continuously in several official capacities from 1953 to 1969 and he was elected to Honorary Membership in 1969.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméLa Photogrammetric Society a été fondée en 1952. Excellente occasion pour faire le point qu'un vingtiéme anniversaire, a estimé le Conseil de la Société; pour rappeler les circonstances de sa naissance, les étapes de sa croissance et les décisions importantes prises depuis 1952. Ce qu'on invita Paul Lamboit à faire. Son exposé resitue la naissance et le développement de la Société dans le contexte national et international de la photogrammétrie; la relation qu'il fait des décisions prises entre 1947 et 1952 intéressera particulièrement ceux qui s'occupent d'histoire de la photogrammétrie.Ce rapport d'abord publié en édition limitée en 1971, a suscité un intérêt suffisant pour que l'on se presse en le publiant dans le Photogrammetric Record de le porter à la connaissance d'un plus large public.L'auteur a exercé différentes fonctions de 1953 à 1969 dans l'appareil de la Société. Il a étéélu membre honoraire en 1969.〈section xml:id="abs1-3"〉〈title type="main"〉Zusummenfussung1952 wurde die Britische Gesellschaft für Photogrammetrie gegründet. Der Rat der Gesellschaft erwog, dass der zwanzigste Jahrestag eine günstige Gelegenheit sei, um die Ereignisse, die zur Gründung der Gesellschaft führten sowie die bedeutenden Veranstaltungen, die stattfanden und die Entscheidungen, die getroffen wurden, darzustellen. Aus diesem Grunde wurde Paul Lamboit eingeladen, diesen historischen Rückblick zu schreiben. Er hat dabei die Gründung und die Entwicklung der Gesellschaft in den nationalen und internationalen photogrammetrischen Zusammenhang gestellt nd sein Bericht über die zwischen 1947 und 1972 erfolgten Beratungen wird für an unserer Sache interessierte Historiker sehr aufschlussreich sein.Diese Zusammenstellung wurde erstmals in einer begrenzten Auflage im Jahre 1971 veröffentlicht. Genügend Interesse wurde inzwischen bekundet, um eine weitergehende Verteilung mit Hilfe des Photogrammetric Record zu veranlassen.Der Autor diente der Gesellschaft kontinuierlich in verschiedenen Ämtern von 1953 bis 1969, wo er aum Ehrenmitglied gewählt wurde.

Notes: Architecture at the Maya archaeological site of Uxmal in Yucatan, Mexico has been documented since the 17th century by historians, archaeologists, illustrators, photographers, and most recently photogrammetrists. This paper reviews the work of the major contributors to recording of architecture at Uxmal with a particular focus on the 19th century stereophotography of Alice and Augustus Le Plongeon who worked to record all the standing architecture at Uxmal, and the close range stereophotogrammetric projects that recorded the Adivino Pyramid during the late 20th century.

Notes: This article presents a complete mathematical model, which translates discrepancies between two orthophotographs created from different photographs, into precise corrections of the Digital Elevation Model (DEM). These corrections are the differences from the real surface and, if applied over the existing DEM, can produce a more accurate one. The mathematical model is straightforward, and is not approximate, and therefore there is no need for iterations.Possible applications include checking of automatically created DEMs, refinement of existing DEMs using aerial photographs and update of orthophotographs based on the previous DEM and new imagery.

Notes: A scholarly account of the formative discussions, the founding and the first 20 years of the Photogrammetric Society was published in 1971 and republished in 1974. This present review concentrates on the latter years of the life of the Photogrammetric Society prior to its merger with the Remote Sensing Society in 2001.The authors joined the Photogrammetric Society in 1960 and were conspicuous in its affairs for many years. Although both occupied the Society's presidential chair, they also fulfilled several other roles in its efficient management. Atkinson's first contribution to the Photogrammetric Record was published in 1968 and Newton's in 1971.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn a publié en 1971 un compte-rendu détaillé des 20 premières années de la “Photogrammetric Society”, à commencer par les discussions qui présidèrent è sa fondation. Ce récit fut republié en 1974. On se focalise dans cet article sur les dernières années d'activité de la “Photogrammetric Society” qui aboutirent à sa fusion avec la “Remote Sensing Society” en 2001.Les deux auteurs adhérèrent à la “Photogrammetric Society” en 1960 et y furent d‘éminents animateurs pendant de nombreuses années. Tous deux occupèrent le poste de président de cette Association mais remplirent égulement plusieurs autres fonctions qui contribuèrent à une gestion efficace. La première intervention d'Atkinson dans le Photogrummetric Record remonte à 1968, et celle de Newton à 1971.〈section xml:id="abs1-3"〉〈title type="main"〉ZusummenfussungEine wissenschaftliche Abhandlung über die Diskussionen zur Gründung, die Gründung selbst und die ersten 20 Jahre der Photogrammetrischen Gesellschaft wurde in 1971 publiziert und in 1974 wiederholt. Dieser aktulle Rückblick konzentriert sich auf die darauffolgenden Jahre der Photogrammetrischen Gesellschaft bis hin zur Vereinigung mit der Gesellschaft für Fernerkundung in Jahre 2001.Die Autoren wurden 1960 Mitglieder in der Photogrammetrischen Gesellschaft und trugen viele Jahre massgeblich zu deren Aktivitäsidenten der Gesellschaft auch verschiedene andere Aufgaben im Management wahrgenommen. Der erste Beitrag von Atkinson im Photogrammetric Record erschien 1968, der erste von Newton in 1971.

Notes: The determination of the attitude, the position and the intrinsic geometric characteristics of the camera is recognised as the fundamental photogrammetric problem. It can be summarised as the determination of camera interior and exterior orientation parameters, as well as the determination of 3D coordinates of object points. The term “exterior orientation” of an image refers to its position and orientation related to an exterior (object space) coordinate system. Several methods can be applied to determine the parameters of the orientation of one, two or more photos. The orientation can be processed in steps (as relative and absolute orientation) but simultaneous methods (such as bundle adjustments) are now available in many software packages. Several methods have also been developed for the orientation of single images. They are based in general on geometric and topological characteristics of imaged objects.This paper presents a survey of classical and modern methods for the determination of the exterior parameters in photogrammetry, some of which are available as software packages (with practical examples) on the Internet. The methods presented are classified in three principal groups. In the first. a selection of approximate methods for applications that do not require great accuracy is presented. Such methods are also used to calculate values required for iterative processes. In the second group, standard point-bused methods derived from collinearity, coplanarity or coangularity conditions are briefly reviewed, followed by line-based approaches. The third group represents orientation methods based on constraints and on concepts of projective geometry, which are becoming of increasing interest for photogrammetrists. In the last section, the paper gives a summary of existing strategies for automatic exterior orientation in aerial photogrammetry.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméLa détermination de l'attitude, de la position et des caractéristiques intrinsèques de la chambre photographique constitue un problème fondamental en photogrammétrie. Il se résume à la détermination des paramètres de l'orientation de la chambre de prise de vue (paramètres des orientations externe et interne), ainsi qu'à la détermination des coordonnées 30 des points de l'objet. L'orientation externe se rapporte à la détermination de la position et de l'orientation d'une chambre par rapport à un système externe de coordonnées. Différentes méthodes peuvent être utilisées pour calculer les éléments dorientation externe d'une photo, d'un couple ou de plusieurs photos. Le calcul de l'orientation peut être réalisé par étapes (par exemple les orientations relative et absolue) mais les méthodes simultanées (la compensation par faisceaux par exemple) sont actuellement proposées dans la plupart des logiciels. Plusieurs méthodes ont aussi été développées pour l'orientation d'images isolées. Ells sont basées en général sur les caactéristiques géométriques et topologiques des objets photographiés.Dans cet article on présente un ensemble de méthodes classiques et modernes pour la détermination des paramètres de l'orientation externe, certaines d'entre elles étant téléchargeables sous la forme d'applications sur Internet. Les méthodes présentées sont classées en trois groupes principaux. Le premier groupe contient une sélection de méthodes approximatives utilisées d'habitude quand une grande précision n'est pas exigée, ou encore pour calculer des vuleurs approchées des paramètres extrinsèques requises pour les méthodes itératives rigoureuses. Dans le deuxième groupe, on rappelle brièvement les jondements des méthodes basées sur les conditions photogrammétriques fondamentales (la colinéarité, la coplanéité et la coangularité). Dans ce groupe, les méthodes basées sur l'extraction des points ou des lignes sont également abordées. Le troisième groupe traite des méthodes d'orientation basées sur les contraintes et les concepts de la géométrie projective, de plus en plus utilisées par les photogrammètres. Le dernier paragraphe se rapporte aux méthodes destinées à automatiser le calcul de l'orientation externe en photogrammétrie aérienne.〈section xml:id="abs1-3"〉〈title type="main"〉ZusummenfussungDie Bestimmung der Neigung, der Position und den geometrischen parametern der Kamera wird als das fundamentale Problem der Photogrammetrie angesehen. Es kann zusammenfassend sowohl als die Bestimmung der Parameter der inneren und äusseren Orientierung der Kamera angesehen werden, als auch als die Bestimmung von 3D Koordinaten von Objektpunkten. Der Ausdruck “äussere Orientierung” eines Bildes bezieht sich auf die Lage und Orientierung bezogen auf ein äusseres (Objektraum-) Koordinatensystem. Es können verschiedene Methoden angewandt werden, um die Parameter von einem, zwei oder mehreren Bildern zu bestimmen. Die orientierung kann in Schritten erfolgen, was als Relative und Absolute Orientierung bezeichnet wird, aber auch simultane Methoden, wie die Bündelausgleichung, sind in vielen Softwarepaketen implementiert. Es wurden auch Methoden für die Orientierung von Einzelbildern entwickelt, die geometrische und topologische Eigenschaften der abgebildeten Objekte nutzen. In diesem Beitrag wird Beitrag wird eine Studie klassischer und moderner Methoden der Photogrammetrie zur Bestimmung der Parameter der äßeren Orientierung vorgestellt, wovon einige in Softwarepaketen zur Verfügung stehen, die von praktischen Beispielen im Internet ergänzt werden. Die untersuchten Methoden werden in drei Hauptgruppen eingeteilt. In einer ersten Gruppe werden Näherungslösungen vorgestellt, die für Anwendungen mit geringen Genauigkeitsanforderungen geeignet sind. Diese Methoden werden ansonsten für die Näherngswertberechunggen für iterative Prozesse verwendet. IN der zweiten Gruppe werden zuerst die punktbasierten Standardmethoden vorgestellt, die von Bedingungen zur Kollinearität. Koplanarität und Kowinkligkeit abgeletet sind. Danach folgen linienbasierte Ansätze. Die dritte Gruppe umfasst Orientierungsmethoden, die auf Zwangsbedingungen und auf Konzepte der projektiven Geometrie aufbauen, die für Photogrammeter von zunehmendem Interesse sind, Im letzten Abschnitt wird eine Zusammenfassung existierender Strategien für eine automatische äussere orientierung in der Luftbildphotogrammetrie gegeben.

Notes: Fresh ground water is widely distributed in subsurface sediments below the coastal bays of the Delmarva Peninsula (Delaware, Maryland, and Virginia). These conditions were revealed by nearly 300 km of streamer resistivity surveys, utilizing a towed multichannel cable system. Zones of high resistivity displayed by inversion modeling were confirmed by vibradrilling investigations to correspond to fresh ground water occurrences. Fresh water lenses extended from a few hundred meters up to 2 km from shore. Along the western margins of coastal bays in areas associated with fine-grained surficial sediments, high-resistivity layers were widespread and were especially pronounced near tidal creeks. Fresh ground water layers were less common along the eastern barrier-bar margins of the bays, where sediments were typically sandy. Mid-bay areas in Chincoteague Bay, Maryland, did not show evidence of fresh water. Indian River Bay, Delaware, showed complex subsurface salinity relationships, including an area with possible hypersaline brines. The new streamer resistivity system paired with vibradrilling in these investigations provides a powerful approach to recovering information required for extension of hydrologic modeling of shallow coastal aquifer systems into offshore areas.

Notes: Rates of ground water recharge and discharge are not well known in the central Everglades. Here we report estimates of ground water recharge and discharge at 15 sites in the Everglades Nutrient Removal Project and in Water Conservation Area 2A (WCA-2A), along with measurements of hydraulic properties of peat at 11 sites. A simple hydrogeologic simulation was used to assess how specific factors have influenced recharge and discharge. Simulations and measurements agreed that the highest values of recharge and discharge occur within 600 m of levees, the result of ground water flow beneath levees. There was disagreement in the interior wetlands of WCA-2A (located 〉 1000 m from levees) where measurements of recharge and discharge were substantially higher than simulated fluxes. A five-year time series (1997 to 2002) of measured fluxes indicated that recharge and discharge underwent reversals in direction on weekly, monthly, and annual timescales at interior sites in WCA-2A. Ground water discharge tended to occur during average to moderately dry conditions when local surface water levels were decreasing. Recharge tended to occur during moderately wet periods or during very dry periods just as water levels began to increase following precipitation or in response to a pulse of surface water released from water-control structures by water managers. Discharge also tended to occur at sites in the wetland interior for ∼1 week preceding the arrival of the surface water pulse. We conclude that ground water recharge and discharge vary cyclically in the interior wetlands of the central Everglades, driven by the differential responses of surface water and ground water to annual, seasonal, and weekly trends in precipitation and operation of water-control structures.

Notes: Despite the central management of Israel's water resources and the highly planned strategy for a sustainable water supply, Israel has twice faced an acute water crisis during the past decade. Although the visible problem is related to a lack of additional quantities of water, the deterioration of water quality appears to be endangering the future use of available water quantities as well. A long-term policy of ground water mining (translated to salt water encroachments), and irrigation with relatively saline water and recycled waste water, among other damage, account for this deterioration. Enhanced flushing of the salt and contaminant load from the aquifers (using various techniques) is proposed as a solution to the problem.

Notes: Predicting the future performance of horizontal wells under varying pumping conditions requires estimates of basic aquifer parameters, notably transmissivity and storativity. For vertical wells, there are well-established methods for estimating these parameters, typically based on either the recovery from induced head changes in a well or from the head response in observation wells to pumping in a test well. Comparable aquifer parameter estimation methods for horizontal wells have not been presented in the ground water literature. Formation parameter estimation methods based on measurements of pressure in horizontal wells have been presented in the petroleum industry literature, but these methods have limited applicability for ground water evaluation and are based on pressure measurements in only the horizontal well borehole, rather than in observation wells. This paper presents a simple and versatile method by which pumping test procedures developed for vertical wells can be applied to horizontal well pumping tests. The method presented here uses the principle of superposition to represent the horizontal well as a series of partially penetrating vertical wells. This concept is used to estimate a distance from an observation well at which a vertical well that has the same total pumping rate as the horizontal well will produce the same drawdown as the horizontal well. This equivalent distance may then be associated with an observation well for use in pumping test algorithms and type curves developed for vertical wells. The method is shown to produce good results for confined aquifers and unconfined aquifers in the absence of delayed yield response. For unconfined aquifers, the presence of delayed yield response increases the method error.

Notes: Flow of nonvolatile nonaqueous phase liquid (NAPL) and aqueous phases that account for mobile, entrapped, and residual NAPL in variably saturated water-wet porous media is modeled and compared against results from detailed laboratory experiments. Residual saturation formation in the vadose zone is a process that is often ignored in multifluid flow simulators, which might cause an overestimation of the volume of NAPL that reaches the ground water. Mobile NAPL is defined as being continuous in the pore space and flows under a pressure gradient or gravitational body force. Entrapped NAPL is defined as being occluded by the aqueous phase, occurring as immobile ganglia surrounded by aqueous phase in the pore space and formed when NAPL is replaced by the aqueous phase. Residual NAPL is defined as immobile, nonwater entrapped NAPL that does not drain from the pore spaces and is conceptualized as being either continuous or discontinuous. Free NAPL comprises mobile and residual NAPL. The numerical model is formulated on mass conservation equations for oil and water, transported via NAPL and aqueous phases through variably saturated porous media. To account for phase transitions, a primary variable switching scheme is implemented for the oil-mass conservation equation over three phase conditions: (1) aqueous or aqueous-gas with dissolved oil, (2) aqueous or aqueous-gas with entrapped NAPL, and (3) aqueous or aqueous gas with free NAPL. Two laboratory-scale column experiments are modeled to verify the numerical model. Comparisons between the numerical simulations and experiments demonstrate the necessity to include the residual NAPL formation process in multifluid flow simulators.

Notes: Land subsidence due to subsurface fluid (water, gas, oil) withdrawal is often predicted by either finite element or finite difference numerical models based on coupled poroelastic theory, where the soil is represented as a semi-infinite medium bounded by the traction-free (ground) surface. One of the variables playing a most important role on the final outcome is the flow condition used on the traction-free boundary, which may be assumed as either permeable or impermeable. Although occasionally justified, the assumption of no-flow surface seems to be in general rather unrealistic. A permeable boundary where the fluid pressure is fixed to the external atmospheric pressure appears to be more appropriate. This paper addresses the response, in terms of land subsidence, obtained with a coupled poroelastic finite element model that simulates a distributed pumping from a horizontal aquifer confined between two relatively impervious layers, and takes either a permeable boundary surface, i.e., constant hydraulic potential, or an impermeable boundary, i.e., a zero Neumann flow condition. The analysis reveals that land subsidence is rather sensitive to the flow condition implemented on the traction-free boundary. In general, the no-flow condition leads to an overestimate of the predicted ground surface settlement, which could even be 1 order of magnitude larger than that obtained with the permeable boundary.

Notes: An experiment was conducted to determine if biodegradation of trichloroethylene (TCE) can occur in previously uncontaminated ground water in saturated fractured saprolite (highly weathered material derived from sedimentary rocks). Two undisturbed columns (0.23 m diameter by 0.25 m long) of fractured saprolite were collected from ∼2 m depth at an uncontaminated site on the Oak Ridge Reservation, Oak Ridge, Tennessee. Natural, uncontaminated ground water from the site, which was degassed and spiked with dissolved phase TCE, was continuously pumped through one column containing the natural microbial communities (the biotic column). In a second column, the microorganisms were inhibited and the dissolved phase TCE was added under aerobic conditions (dissolved oxygen conditions 〉 2 ppm). In effluent from the biotic column, reducing conditions rapidly developed and evidence of anaerobic biodegradation of TCE, by the production of cDCE, first appeared ∼31 days after addition of TCE. Reductive dechlorination of TCE occurred after iron-reducing conditions were established and about the same time that sulfate reduction began. There was no evidence of methanogenesis. Analyses using polymerase chain reaction with specific primers sets detected the bacteria Geothrix, Geobacter, and Desulfococcus-Desulfonema-Desulfosarcina in the effluent of the biotic column, but no methanogens. The presence of these bacteria is consistent with iron- and sulfate-reducing conditions. In the inhibited column, there were no indicators of TCE degradation. Natural organic matter that occurs in the saprolite and ground water at the site is the most likely primary electron donor for supporting reductive dechlorination of TCE. The relatively rapid appearance of indicators of TCE dechlorination suggests that these processes may occur even in settings where low oxygen conditions occur seasonally due to changes in the water table.

Notes: A number of methods involving indicator geostatistics were combined in a methodology for characterizing and modeling multiscale heterogeneity. The methodology circumvents sources of bias common in data from borehole logs. We applied this methodology to the complex heterogeneity within a regional system of buried valley aquifers, which occurs in the western glaciated plains of North America and includes the Spiritwood Aquifer. The region is conceptualized as having a hierarchical organization with three facies assemblage types (large-scale heterogeneity) and two facies types within each assemblage (small-scale heterogeneity). We statistically characterized the sedimentary architecture at both scales, formulated indicator correlation models from those characterizations, and used the models to simulate the architecture in a multiscale realization. We focused on the interconnectivity of units creating higher-permeability pathways. Higher-permeability pathways span the realization even though the proportion of higher-permeability facies is less than the percolation threshold. Thus, geologic structures as represented in the indicator correlation models create interconnectivity above that which would occur if the higher-permeability facies were randomly placed. This amount of interconnection among higher-permeability facies within the multiscale realization is consistent with that suggested in prior hydraulic and geochemical studies of the regional system.

Notes: We examined a large (240 km2) northern Appalachian bituminous coal basin (Irwin Syncline, Westmoreland County, Pennsylvania) comprising 27 mine complexes with nine major (〉 2.5 × 103 L/min) discharges. The synclinal basin was divided into seven subbasins based on equilibrium hydraulic relationships established during the past 25 years. Recharge rates, mine pool velocity, and residence times respond to hydraulic changes in the overburden induced by mine subsidence. The estimated maximum depth for subsidence fractures is 60 m (30 times mined thickness) with recharge rates decreasing significantly in subbasins with thicker overburden (〉 75 m). Calculated subbasin recharge rates range from 2 to 6 × 10−4 L/min/m2 and are significantly lower than the previously used rate for the basin. Residence time of ground water in the Irwin subbasins calculated using average linear velocity ranged from one to five years and were more consistent with field observations than estimates obtained using discharge and basin volume area. A positive correlation (r2= 0.80) exists between net alkalinity of the mine water-impacted discharges and residence time in the mine pools. Our results for the Irwin coal basin suggest that use of a subbasin approach incorporating overburden depth, mining methodology, and the extent of postmining inundation will lead to improved determination of ground water flow parameters in mined watersheds in northern Appalachia and elsewhere.

Notes: Flow from some springs in former glacial lakebeds of the Upper Midwest is extremely steady throughout the year and does not increase significantly after precipitation events or seasonal recharge. Analytical and simplified numerical models of spring systems were used to determine whether preferential ground water flow through high-permeability features in shallow sandstone aquifers could produce typical values of spring discharge and the unusually steady rates of spring flow. The analytical model is based on a one-dimensional solution for periodic ground water flow. Solutions to this model suggest that it is unlikely that a periodic forcing due to seasonal variations in areal recharge would propagate to springs in a setting where high-permeability features exist. The analytical model shows that the effective length of the aquifer, or the length of flowpaths to a spring, and the total transmissivity of the aquifer have the greatest potential to impact the nature of spring flow in this setting. The numerical models show that high-permeability features can influence the magnitude of spring flow and the results demonstrate that the lengths of ground water flowpaths increase when high-permeability features are explicitly modeled, thus decreasing the likelihood for temporal variations in spring flow.

Notes: This investigation was undertaken to develop an integrated method of downhole fracture characterization using a tracer. The method presented can be used to locate water-bearing fractures that intersect the well, to determine the ambient fracture flow rate and hydraulic head, and to calculate fracture transmissivity. The method was tested in two fractured crystalline bedrock wells located at the University of Connecticut in Storrs. The method entails injecting a tracer (uranine dye) into the well, while at the same time water is pumped out of the well. After steady-state conditions are reached, a borehole tracer concentration profile is developed. The dilution of the tracer is used to locate the inflowing fractures and to determine their flow rate. The fracture flow rate, plus the drawdown in the well, is then used to determine the fracture hydraulic head, transmissivity, and ambient flow rate.

Notes: A key factor in the long-term viability of aquifer storage recovery (ASR) is the extent of mineral solution interaction between two dissimilar water types and consequent impact on water quality and aquifer stability. We collected geochemical and isotopic data from three observation wells located 25, 65, and 325 m from an injection well at an experimental ASR site located in a karstic, confined carbonate aquifer in South Australia. The experiment involved five major injection cycles of a total of 2.5 × 105 m3 of storm water (total dissolved solids [TDS] ∼ 150 mg/L) into the brackish (TDS ∼2400 mg/L) aquifer. ∼60% of the mixture was pumped out during the fifth year of the experiment. The major effect on water quality within a 25 m radius of the injection well following injection of storm water was carbonate dissolution (35 ± 6 g of CaCO3 dissolved/m3 of aquifer) and sulfide mineral oxidation (50 ± 10 g as FeS2/m3 after one injection). 〈 0.005% of the total aquifer carbonate matrix was dissolved during each injection event, and ∼0.2% of the total reduced sulfur. Increasing amounts of ambient ground water was entrained into the injected mixture during each of the storage periods. High 14CDIC activities and slightly more negative δ13CDIC values measured immediately after injection events show that substantial CO2(aq) is produced by oxidation of organic matter associated with injectant. There were no detectable geochemical reactions while pumping during the recovery phase in the fifth year of the experiment.

Notes: Numerical experiments with steady-state ground water flow models show that spiraling flow lines occur in layered aquifers that have different anisotropic horizontal hydraulic conductivities in adjacent layers. Bundles of such flow lines turning in the same direction can be referred to as ground water whirls. An anisotropic layered block in a field of uniform horizontal flow results in one or more whirls with their axes in the uniform flow direction. The number of whirls depends on the number of interfaces between layers with different anisotropic properties. For flow to a well in an aquifer consisting of two anisotropic layers, with perpendicular major principal directions, whirls are found to occur in quadrants that are bounded by the principal directions of the hydraulic conductivity. The combined effect of flow to a well and a layered anisotropy implies that a single well in a system with a single anisotropic layer within an otherwise isotropic aquifer causes eight whirls. All adjacent whirls rotate in opposite directions.

Notes: Desorption is one of the most critical processes affecting the effectiveness of soil and ground water remediation. None of the currently adopted desorption models can accurately quantify desorption of low-hydrophobicity organic chemicals, and thus could potentially mislead remediation design and decision-making. A recently developed dual-equilibrium desorption (DED) model was found to be much more accurate in quantifying desorption. A screening-level transport model, DED-Transport, was developed to simulate the DED effect on behaviors of organic contaminant plumes during remediation. DED-Transport requires only simple parameters, but is applicable to many remediation scenarios. DED-Transport can be used as a decision-support tool in site remediation to more precisely predict the time required for cleanup.

Notes: Adverse impacts on the health of some fish populations, such as skewed sex distributions, have been noted in surface waters and in laboratory experiments with relatively low concentrations (above 25 ng/L) of natural estrogen (17 β-estradiol—E2). Sources of E2 to surface and ground waters can include avian, human, and mammalian waste products. The Ozark Plateau Aquifer (OPA) is a karstic basin that receives a significant portion of its water through losing reaches of rivers. Thus, there is a direct connection between surface water and ground water. The OPA was targeted for an E2 study to assess the potential for adverse health effects to aquatic organisms living in the system. Eight springs, which drain the aquifer, were sampled quarterly. The concentrations of E2 in the OPA ranged from 13 to 80 ng/L. For any one sampling event, the concentrations of E2 at the spring waters were statistically similar; however, the concentrations of E2 at all springs varied throughout the year. At Maramec Spring, one of the larger springs, the E2 concentration, was correlated with discharge. Based on the correlation between discharge and E2 concentration, aquatic organisms living in the plateau or in its discharged waters, including the threatened southern cavefish T. subterraneus, are exposed to concentration of E2 above 25 ng/L ∼60% of the time. This implies that organisms living in karst basins throughout the OPA are likely exposed to E2 concentrations that may adversely impact their reproductive success for a significant portion of each year.

Notes: In this study, we use borehole temperature data and stable isotopes to delineate the flow system and estimate the effect of urbanization in the Nagaoka area of Japan. Temperature profiles were measured four times in observation wells during the period 2000–2001 and compared with those measured in the same wells during the period 1977–1983 (Taniguchi 1986). Water was sampled in both observation and pumping wells during the same period. The temporal and spatial variability in temperature indicate clearly the effect of urban warming and heavy pumping on the ground water system. Urban warming caused higher temperatures recently as compared to the older values, and pumping caused induced recharge from the river to the ground water. The stable isotope data show the ground water flow system is divided into shallow, intermediate, and deep systems, and that land use and infiltration rate are affecting the shallow flow system.

Notes: This paper describes a series of experiments that tested the ability of the electrical resistivity tomography (ERT) method to locate correctly wet and dry fractures in a meso-scale model. The goal was to develop a method of monitoring the flow of water through a fractured rock matrix.The model was a four by six array of limestone blocks equipped with 28 stainless steel electrodes. Dry fractures were created by placing pieces of vinyl between one or more blocks. Wet fractures were created by injecting tap water into a joint between blocks. In electrical terms, the dry fractures are resistive and the wet fractures are conductive. The quantities measured by the ERT system are current and voltage around the outside edge of the model. The raw ERT data were translated to resistivity values inside the model using a three-dimensional Occam's inversion routine. This routine was one of the key components of ERT being tested.The model presented several challenges. First, the resistivity of both the blocks and the joints was highly variable. Second, the resistive targets introduced extreme changes the software could not precisely quantify. Third, the abrupt changes inherent in a fracture system were contrary to the smoothly varying changes expected by the Occam's inversion routine. Fourth, the response of the conductive fractures was small compared to the background variability.In general, ERT was able to locate correctly resistive fractures. Problems occurred, however, when the resistive fracture was near the edges of the model or when multiple fractures were close together. In particular, ERT tended to position the fracture closer to the model center than its true location. Conductive fractures yielded much smaller responses than the resistive case. A difference-inversion method was able to correctly locate these targets.

Notes: Streambed temperature mapping, hydraulic testing using minipiezometers, and geochemical analyses of interstitial water of the streambed were used to delineate the pattern of ground water discharge in a sandy streambed and to develop a flux-based conceptual model for ground water/surface water interactions. A new and simple empirical method was used to relate fluxes obtained from minipiezometer data to streambed temperatures. The relationship allowed flux to be calculated at locations where only streambed temperature measurements were made. Slug testing and potentiomanometer measurements at 34 piezometers indicated ground water discharge ranged from 0.03 to 446 L/m2/day (and possibly as high as 7060 L/m2/day) along a 60 m long by 11 to 14 m wide reach of river. Complex but similar plan-view patterns of flux were calculated for both summer and winter using hundreds of streambed temperatures measured on a 1 by 2 m grid. The reach was dominated by ground water discharge and 5% to 7% of the area accounted for ∼20% to 24% of the total discharge. 〈 12% of the total area consisted of recharge zones or no-discharge zones. A conceptual model for ground water/surface water interactions consisting of five different behaviors was developed based on the magnitude and direction of flux across the surface of the streambed. The behaviors include short-circuit discharge (e.g., high-flow springs), high discharge (e.g., preferential flowpaths), low to moderate discharge, no discharge (e.g., horizontal hyporheic or ground water flow), and recharge. Geological variations at depth played a key role in determining which type of flow behavior occurred in the streambed.

Notes: Many sites of ground water contamination rely heavily on complex numerical models of flow and transport to develop closure plans. This complexity has created a need for tools and approaches that can build confidence in model predictions and provide evidence that these predictions are sufficient for decision making. Confidence building is a long-term, iterative process and the author believes that this process should be termed model validation. Model validation is a process, not an end result. That is, the process of model validation cannot ensure acceptable prediction or quality of the model. Rather, it provides an important safeguard against faulty models or inadequately developed and tested models. If model results become the basis for decision making, then the validation process provides evidence that the model is valid for making decisions (not necessarily a true representation of reality). Validation, verification, and confirmation are concepts associated with ground water numerical models that not only do not represent established and generally accepted practices, but there is not even widespread agreement on the meaning of the terms as applied to models. This paper presents a review of model validation studies that pertain to ground water flow and transport modeling. Definitions, literature debates, previously proposed validation strategies, and conferences and symposia that focused on subsurface model validation are reviewed and discussed. The review is general and focuses on site-specific, predictive ground water models used for making decisions regarding remediation activities and site closure. The aim is to provide a reasonable starting point for hydrogeologists facing model validation for ground water systems, thus saving a significant amount of time, effort, and cost. This review is also aimed at reviving the issue of model validation in the hydrogeologic community and stimulating the thinking of researchers and practitioners to develop practical and efficient tools for evaluating and refining ground water predictive models.

Notes: Measurement and analysis of aquifer-system compaction have been used to characterize aquifer and confining unit properties when other techniques such as flow modeling have been ineffective at adequately quantifying storage properties or matching historical water levels in environments experiencing land subsidence. In the southeastern coastal plain of Virginia, high-sensitivity borehole pipe extensometers were used to measure 24.2 mm of total compaction at Franklin from 1979 through 1995 (1.5 mm/year) and 50.2 mm of total compaction at Suffolk from 1982 through 1995 (3.7 mm/year). Analysis of the extensometer data reveals that the small rates of aquifer-system compaction appear to be correlated with withdrawals of water from confined aquifers. One-dimensional vertical compaction modeling indicates measured compaction is the result of nonrecoverable hydrodynamic consolidation of the fine-grained confining units and interbeds, as well as recoverable compaction and expansion of coarse-grained aquifer units. The calibrated modeling results indicate that nonrecoverable specific storage values decrease with depth and range from 1.5 × 10−5/m for aquifer units to 1.5 × 10−4/m for confining units and interbeds. The aquifer and Potomac system recoverable specific storage values were all estimated to be 4.5 × 10−6/m, while the confining units and interbeds had values of 6.0 × 10−6/m. The calibrated vertical hydraulic conductivity values of the confining units and interbeds ranged from 6.6 × 10−4m/year to 2.0 × 10−3 m/year. These parameter values will be useful in future management and modeling of ground water in the Virginia Coastal Plain.

Notes: Ferric iron encrustations are a common problem that seriously affects the performance of wells and drains. Their formation is induced by the mixing of reduced ground water containing ferrous iron with oxic shallow ground water and exposure to air. The process of ferrous iron oxidation is a kinetically controlled reaction. The reaction rate has a quadratic dependency on pH. The precipitating oxides have an autocatalytic effect that further enhances reaction progress. This paper describes the application of kinetic models to the problem of encrustation formation. Influences of pH, residence time, and autocatalysis were modeled. The overall influence of the autocatalytic reaction path is particularly strong when initial amounts of iron oxides are present. Autocatalysis provides a good explanation on the development of well yield commonly measured in the field. Encrustation precipitation is slow at first, but speeds up after a sufficient amount of iron oxide has built up. An incomplete removal of iron oxide encrustations during rehabilitation leads to a renewed increase in catalytic efficiency and encrustation precipitation.

Notes: Prevention of acid mine drainage at surface coal mines in the Appalachian region relies to an extent on minimizing ground water contact with acid-forming materials, and maximizing ground water contact with alkalinity-yielding materials. Acid-forming materials are often selectively handled to minimize or prevent contact with ground water. Controlling ground water contact with acidic or alkaline materials depends on forecasting the level and range of fluctuation of the postmining water table within the mine backfill. Physical measurements and aquifer testing of more than 120 wells from 18 reclaimed mines in Kentucky, Ohio, Pennsylvania, and West Virginia have led to improved forecasting of the postmining ground water system. Factors that influence the ground water regime include spoil lithology and particle size, age of reclamation, spoil thickness, distance from the final highwall, and pit floor dip angle and direction. Spoil hydraulic conductivity (K) exhibits a 95% confidence interval range of six orders of magnitude about a mean K of 1.7 × 10−5 m/sec. Spoil aquifer saturated thickness is related to the overall thickness of the spoil, the lithology of the spoil, dip of the pit floor, and distance to the highwall. Saturated spoil thickness has a 95% confidence interval of 2.2 to 3.6 m about the mean of 2.9 m. The predicted saturated zone averages 19% of the total spoil thickness.

Notes: Hypersaline calcium/chloride shield brines are ubiquitous in Canada and areas of northern Europe. The major questions relating to these fluids are the origin of the solutes and the concentration mechanism that led to their extreme salinity. Many chemical and isotopic tracers are used to solve these questions. For example, lithium isotope systematics have been used recently to support a marine origin for the Yellowknife shield brine (Northwest Territories). While having important chemical similarities to the Yellowknife brine, shield brines from the Sudbury/Elliot Lake (Ontario) and Thompson/Snow Lake (Manitoba) regions, which are the focus of this study, exhibit contrasting lithium behavior.Brine from the Sudbury Victor mine has lithium concentrations that closely follow the sea water lithium-bromine concentration trajectory, as well as δ6Li values of approximately—28 %o. This indicates that the lithium in this brine is predominantly marine in origin with a relatively minor component of crustal lithium leached from the host rocks. In contrast, the Thompson/Snow Lake brine has anomalously low lithium concentrations, indicating that it has largely been removed from solution by alteration minerals. Furthermore, brine and nonbrine mine waters at the Thompson mine have large δ6Li variations of ∼30 %o, which primarily reflects mixing between deep brine with δ6Li of—35 ± 2‰ and near surface mine water that has derived higher δ6Li values through interactions with their host rocks. The contrary behavior of lithium in these two brines shows that, in systems where it has behaved conservatively, lithium isotopes can distinguish brines derived from marine sources.

Notes: Today, models are ubiquitous tools for ground water analyses. The intent of this paper is to explore philosophically the role of the conceptual model in analysis. Selection of the appropriate conceptual model is an a priori decision by the analyst. Calibration is an integral part of the modeling process. Unfortunately a wrong or incomplete conceptual model can often be adequately calibrated; good calibration of a model does not ensure a correct conceptual model. Petroleum engineers have another term for calibration; they refer to it as history matching. A caveat to the idea of history matching is that we can make a prediction with some confidence equal to the period of the history match. In other words, if we have matched a 10-year history, we can predict for 10 years with reasonable confidence; beyond 10 years the confidence in the prediction diminishes rapidly. The same rule of thumb applies to ground water model analyses. Nuclear waste disposal poses a difficult problem because the time horizon, 1000 years or longer, is well beyond the possibility of the history match (or period of calibration) in the traditional analysis. Nonetheless, numerical models appear to be the tool of choice for analyzing the safety of waste facilities. Models have a well-recognized inherent uncertainty. Performance assessment, the technique for assessing the safety of nuclear waste facilities, involves an ensemble of cascading models. Performance assessment with its ensemble of models multiplies the inherent uncertainty of the single model. The closer we can approach the idea of a long history with which to match the models, even models of nuclear waste facilities, the more confidence we will have in the analysis (and the models, including performance assessment). This thesis argues for prolonged periods of observation (perhaps as long as 300 to 1000 years) before a nuclear waste facility is finally closed.

Notes: In a recent field study of ground water/surface water interaction between a bedrock stream and an underlying fractured rock aquifer, it was determined that the majority of ground water discharge occurred through sparsely located vertical fractures. In this paper, the dominant mechanisms governing ground water/surface water exchange in such an environment are investigated using a numerical model. The study was conducted using several conceptual models based on the field study results. Although the field results provided the motivation for the modeling study, it was not intended to match modeling and field results directly. In addition, the extent of capture zones for discharging or recharging fractures was explored. The results of this study are intended to provide a better understanding of contaminant migration in the vicinity of bedrock streams. Based on the numerical results, the rate of ground water discharge (or recharge) was found to depend on the aperture size of the discharging feature, and on the distribution of hydraulic head with depth within the fracture network. It was determined that the extent of both the capture zone and reverse capture zone for an individual fracture can be extremely large, and will be determined by the height of the stream stage, the fracture apertures of the network, and the hydraulic-head distribution within the network. Because both the stream stage and the hydraulic-head distribution are transient, the size of the capture zone and/or the reverse capture zone for an individual fracture may change significantly over time. As a result, the migration path for contaminants within the fracture network and between the surface and subsurface will also vary significantly with time.

Notes: Measurements of dissolved gases have numerous applications in ground water hydrology, and it is now possible to measure the total dissolved gas pressure in situ using a probe. Dissolved gas pressure is measured by submerging a headspace volume with a gas-permeable membrane, allowing dissolved gases in the water to equilibrate with gases in the headspace, then measuring the pressure in the headspace with a pressure transducer. Total dissolved gas pressure (TGP) probes have many potential uses in ground water studies employing dissolved gases, including: (1) determining approximate excess air levels, which may provide information about the time and location of recharge; (2) screening wells for air contamination, which can compromise the accuracy of dissolved gas tracer techniques: (3) detecting a trapped gas phase, which can significantly reduce hydraulic conductivity and impede the transport of dissolved solutes and gases; (4) enabling the use of gas-filled passive diffusion samplers for determining accurate dissolved gas concentrations; and (5) determining relative concentrations of CH4 and CO2 when they are known to be highly abundant. Although TGP probes designed for surface water have been available for several years, TGP probes suitable for ground water applications have only recently become available. Herein we present what are, to our knowledge, the first reported ground water dissolved gas data collected using a TGP probe. We also explain the basic operating principles of these probes and discuss the potential applications listed.

Notes: The application of in situ chemical oxidation for dense, nonaqueous phase liquid (DNAPL) remediation requires delivery of substantial levels of oxidant chemicals into the subsurface to degrade target DNAPLs and to satisfy natural oxidant demand. This practice can raise questions regarding changes in subsurface conditions, yet information regarding potential effects, especially at the field scale, has been lacking. This paper describes an evaluation of the effects on metals associated with in situ chemical oxidation using potassium permanganate at Launch Complex 34 (LC34), Cape Canaveral Air Station, Florida. At LC34, high concentrations of permanganate (1 to 2 wt%) were injected into the subsurface as part of a demonstration of DNAPL remediation technologies. In a companion experimental effort at the Colorado School of Mines, field samples were characterized and laboratory batch and mini-column studies were completed to assess effects of permanganate oxidation on metals in the subsurface one year after completion of the field demonstration. Results indicated there was potential for long-term immobilization of a portion of introduced manganese and no treatment-induced loss in subsurface permeability due to deposition of manganese oxides particles, which are a product of the oxidation reactions. Permanganate treatment did cause elevated manganese, chromium, and nickel concentrations in site ground water within the treated region. Some of these metals effects can be attenuated during downgradient flow through uncontaminated and untreated aquifer sediments.

Notes: Naturally occurring long-term mean annual base recharge to ground water in Nebraska was estimated with the help of a water-balance approach and an objective automated technique for base-flow separation involving minimal parameter-optimization requirements. Base recharge is equal to total recharge minus the amount of evapotranspiration coming directly from ground water. The estimation of evapotranspiration in the water-balance equation avoids the need to specify a contributing drainage area for ground water, which in certain cases may be considerably different from the drainage area for surface runoff. Evapotranspiration was calculated by the WREVAP model at the Solar and Meteorological Surface Observation Network (SAMSON) sites. Long-term mean annual base recharge was derived by determining the product of estimated long-term mean annual runoff (the difference between precipitation and evapotranspiration) and the base-flow index (BFI). The BFI was calculated from discharge data obtained from the U.S. Geological Survey's gauging stations in Nebraska. Mapping was achieved by using geographic information systems (GIS) and geostatistics. This approach is best suited for regional-scale applications. It does not require complex hydrogeologic modeling nor detailed knowledge of soil characteristics, vegetation cover, or land-use practices. Long-term mean annual base recharge rates in excess of 110 mm/year resulted in the extreme eastern part of Nebraska. The western portion of the state expressed rates of only 15 to 20 mm annually, while the Sandhills region of north-central Nebraska was estimated to receive twice as much base recharge (40 to 50 mm/year) as areas south of it.

Notes: A digital procedure to estimate recharge/discharge rates that requires relatively short preparation time and uses readily available data was applied to a setting in central Wisconsin. The method requires only measurements of the water table, fluxes such as stream baseflows, bottom of the system, and hydraulic conductivity to delineate approximate recharge/discharge zones and to estimate rates. The method uses interpolation of the water table surface, recharge/discharge mapping, pattern recognition, and a parameter estimation model. The surface interpolator used is based on the theory of radial basis functions with thin-plate splines. The recharge/discharge mapping is based on a mass-balance calculation performed using MODFLOW. The results of the recharge/discharge mapping are critically dependent on the accuracy of the water table interpolation and the accuracy and number of water table measurements. The recharge pattern recognition is performed with the help of a graphical user interface (GUI) program based on several algorithms used in image processing. Pattern recognition is needed to identify the recharge/discharge zonations and zone the results of the mapping method. The parameter estimation program UCODE calculates the parameter values that provide a best fit between simulated heads and flows and calibration head-and-flow targets. A model of the Buena Vista Ground Water Basin in the Central Sand Plains of Wisconsin is used to demonstrate the procedure.

Notes: We examine the possibility of using the flow dimension identified from constant pressure injection tests as a tool for characterizing the hydraulic conditions of fractured media. The data comes from a low-conductivity crystalline rock site, from depths of up to 450 m, and is obtained with 2 m and 10 m measurement scales. In the analysis, the general solution for n-dimensional flow by Barker (1988) is applied. The results show that the most prominent characteristics of the medium can be identified; that is, linear and sublinear flow dimensions as distinguished from dimensions higher than two. In many cases, however, there is significant difficulty in distinguishing the dimensions n = 2, 2.5, and 3 from each other. This is usually because of the experimental difficulties in achieving the ideal conditions required by the theory during the early part of the experiment. In such cases, a full flow curve is not available for the type-curve fitting. In the nonunique cases the higher dimensions typically correspond to higher, sometimes unrealis-tically high, values of specific storage and to the less reliable and less representative early part of the experiment. Therefore, most of the dimensions in categories n= 3 can be excluded, thus leaving the majority observations in the categories of n= 2 and n = 2–2.5. The dominance of dimension n = 2 is more pronounced for data related to fracture zones in comparison to that related to “average” rock, in particular in the 2 m scale data. The proportion of low (n 〈 1.5) flow dimensions is small, but for the 10 m scale data it is relatively higher at greater depths and corresponds to lower conductivities. For the smaller 2 m scale data, the low dimensions are not linked to greater depths or systematically smaller conductivities, giving preliminary indication of different flow dimension behavior for the two different scales.

Notes: An approach to estimating the uncertainty in model descriptions based on a landscape space to model space mapping concept is described. The approach is illustrated by an application making use of plot scale geophysical estimates of changes in water content profiles to condition a model of recharge to the Sherwood Sandstone Aquifer in the United Kingdom. It is demonstrated that the mapping is highly uncertain and that many different parameter sets give acceptable simulations of the observations. Multiple profile measurements over time offer only limited additional constraints on the mapping. The resulting mapping weights may be used to evaluate uncertainty in the predictions of vadose zone flow dynamics for the site.

Notes: Approaches for modeling lake-ground water interactions have evolved significantly from early simulations that used fixed lake stages specified as constant head to sophisticated LAK packages for MODFLOW. Although model input can be complex, the LAK package capabilities and output are superior to methods that rely on a fixed lake stage and compare well to other simple methods where lake stage can be calculated. Regardless of the approach, guidelines presented here for model grid size, location of three-dimensional flow, and extent of vertical capture can facilitate the construction of appropriately detailed models that simulate important lake-ground water interactions without adding unnecessary complexity. In addition to MODFLOW approaches, lake simulation has been formulated in terms of analytic elements. The analytic element lake package had acceptable agreement with a published LAK1 problem, even though there were differences in the total lake conductance and number of layers used in the two models. The grid size used in the original LAK1 problem, however, violated a grid size guideline presented in this paper. Grid sensitivity analyses demonstrated that an appreciable discrepancy in the distribution of stream and lake flux was related to the large grid size used in the original LAK1 problem. This artifact is expected regardless of MODFLOW LAK package used. When the grid size was reduced, a finite-difference formulation approached the analytic element results. These insights and guidelines can help ensure that the proper lake simulation tool is being selected and applied.

Notes: The beginning of the 21st century has coincided with our recognition that life-sustaining earth cycles are remarkably fine-tuned, and that humans have developed technological abilities to perturb these cycles. Also, inspired by the gifts of freedom and democracy, humans have given themselves laws to exploit nature for profit. The upshot is that nature's balance, governed by immutable physical laws, is being confronted by social laws driven by human aspirations. This conflict and its implications to the human relevance of the earth sciences are explored in the context of an extraordinary tradition of European culture known as public trust.

Notes: Recent research has shown that planting deep-rooted trees, such as poplar, can take up and degrade important ground water pollutants such as trichloroethylene (TCE) as they transpire water from the capillary fringe of shallow contaminated aquifers. The effect of hydrogeologic factors on the minimum plantation area needed to prevent downgradient migration of contaminated ground water is not well known. Accordingly, the objective of this research was to identify the hydrogeologic parameters that control phytoremediation effectiveness. We used a numerical ground water flow model to evaluate the effect that natural variations in hydrogeologic parameters and growing season duration have on the minimum plantation area required for capture. We found that the plantation area that was needed to completely capture a ground water contamination plume was directly proportional to aquifer horizontal hydraulic conductivity, saturated thickness, and ground water gradient. The plantation area needed for capture increased non-linearly with increasing plume width, aquifer anisotropy, and decreasing growing season duration. The plantation area needed for capture was generally insensitive to aquifer-specific yield and storativity. Steady-state simulations can be used to predict the plantation area needed for capture in many applications. A particularly important finding of this work is that evapotranspiration fluxes through plantations appropriately sized to contain the plume substantially exceeded the ground water flux through the plume itself.

Notes: Two of the biggest drawbacks of using permeable reactive barriers (PRBs) to treat contaminated ground water are the high capital cost of installation, particularly when the contaminated ground water is deep below ground surface, and the uncertainty of whether or not PRBs remain effective for the long time scales (e.g., decades) needed for many contaminant plumes. The use of an injection-extraction treatment well pair (IETWP) for capture and treatment of contaminated ground water can circumvent these difficulties, while still providing many of the same advantages offered by PRBs. In this paper, the hydraulics of IETWPs and PRBs are compared, focusing primarily on the width of the captured plume. It is demonstrated that IETWPs act as hydraulic barriers in a manner similar to PRBs, and that IETWPs provide excellent plume capture. A mathematical expression is presented for the plume capture width of an IETWP oriented perpendicular to the ground water flow direction in a homogeneous aquifer. Also discussed are other practical considerations that might determine whether an IETWP is better suited than a PRB for a particular contaminated site; these considerations include operating and maintenance costs, and the conditions under which an IETWP system can be used for in situ remediation.

Notes: Two environmental tracer methods are applied to the Ti-Tree Basin in central Australia to shed light on the importance of recharge from floodouts of ephemeral rivers in this arid environment. Ground water carbon-14 concentrations from boreholes are used to estimate the average recharge rate over the interval between where the ground water sample first entered the saturated zone and the bore. Environmental chloride concentrations in ground water samples provide estimates of the recharge rate at the exact point in the landscape where the sample entered the saturated zone. The results of the two tracer approaches indicate that recharge rates around one of the rivers and an extensive flood-plain are generally higher than rates of diffuse recharge that occurs in areas of lower topographic relief. Ground water 2H/1H and 18O/16O compositions are all depleted in the heavier isotopes (δ2H = -67%0 to -50%0; 518O = -9.2%0 to -5.7%0) compared with the long-term, amount-weighted mean isotopic composition of rainfall in the area (δ2H = -33.8%0; δ18O = -6.3%0). This indicates that recharge throughout the basin occurs only after intense rainfall events of at least 150 to 200 mm/month. Finally, a recharge map is developed to highlight the spatial extent of the two recharge mechanisms. Floodout recharge to the freshest ground water (TDS 〈1000 mg/L) is ∼1.9 mm/year compared with a mean recharge rate of ∼0.2 mm/year to the remainder of the basin. These findings have important implications for management of the ground water resource.

Notes: The delineation of well capture zones is a basic component of ground water protection. The conventional methodology for capture zone delineation is backward advective particle tracking, often applied under the assumption of a two-dimensional aquifer. The suitability of the conventional approach for complex heterogeneous multi-aquifer systems was investigated, using the Waterloo Moraine aquifer system as an example. It was found that the conventional approach produces irregular particle tracks that require judgment to interpret in a meaningful way, and it can raise questions that may affect the credibility of the capture zone delineation. As an alternative, the potentially powerful but little-used backward-in-time advective-dispersive transport approach was investigated. A key advantage of this approach is its capability to represent local heterogeneities through the dispersion term. The dispersion process has a natural smoothing effect that results in unambiguous capture zones without the need for interpretation, thus enhancing credibility. The question of capture zone validation is also addressed. The meaning of a three-dimensional capture zone is considered, and it is shown that a fully three-dimensional representation of the system is crucial for valid results. The distinction between the maximum extent capture zone and the surface capture zone is also explained. In the case of complex heterogeneous systems, advective particle tracking can be used as an initial screening tool, whereas the more realistic backward-transport modeling approach can be used for final capture-zone delineation.

Notes: Tracer tests represent the most appropriate approach for assessing hydrodispersive parameters such as transversal and longitudinal dispersivities or kinematic porosity on an aquifer scale. They are generally carried out by injecting a tracer in a borehole and measuring its concentration over time in neighboring boreholes by extracted volume sampling or downhole measurements. Logging is one of the most suitable methods for evaluating fissured reservoirs. But short circuits between fractures with different hydraulic potential through boreholes induce mixing phenomena that cannot be avoided without packers. This mixing can shift the breakthrough curves deduced from the logs for each producing fracture and distort determination of their location.The method proposed in this paper aims at measuring the flow rate and the solute breakthrough for hydraulically active fractures, in open boreholes. It involves estimating a velocity profile along the borehole column by the analysis of two successive logs: a shift function according to depth is thus determined by comparison between log portions on each successive one. The velocity gradients reflect the inward or outward flow rates produced by each fracture. On the basis of these flow rates, it is possible to determine the mixing effects inside the borehole and then to plot unbiased breakthrough curves for each producing fracture.This method was applied at a granitic site in the eastern Pyrenees. In spite of some questionable limitations, the results showed that the method seems adapted to situations with many fractures. The precise hydraulic pattern which is obtained at the borehole scale is discussed in terms of a dual porosity model. Furthermore, interpretation of the breakthrough curves for fractures corrected for mixing effects revealed that Peclet numbers are strongly underestimated if this phenomenon is not considered.

Notes: Transport of a conservative compound and two sorbing compounds through fractured chalk was studied using flow-through columns consisting of chalk cores with a single subvertical fracture. Two types of chalk matrix were compared, an oxidized white chalk with low organic carbon content (0.2%), and a gray chalk with a higher organic carbon content (1.3%). Initial rapid breakthrough followed by a delayed approach to a relative concentration of unity for the conservative compound (2,6–difluorobenzoic acid [DFBA]) was clear evidence for diffusion into the porous chalk matrix. Matrix diffusion of DFBA was apparently much greater in the gray chalk columns than in the white chalk columns. Breakthrough curves (BTCs) of the sorbing compounds (2,4,6–tri-bromophenol [TBP] and ametryn [AME]) were retarded in all cases as compared to the conservative compound. Sorption retardation was far greater in the gray chalk as compared with the white chalk, in good agreement with results from batch sorption experiments. BTCs for the conservative compound were relatively nonhysteretic for both white and gray chalk columns. In contrast, BTCs for the sorbing compounds were hysteretic in all cases, demonstrating that sorption was not at equilibrium before desorp-tion began. These experiments suggest that on a field scale, transport of contaminants through fractures in chalk and other fractured porous media will be attenuated by diffusion and sorption into the matrix.

Notes: Models for ground water flow (MODFLOW) and particle tracking (MODPATH) were used to determine ground water flow patterns, principal ground water discharge and recharge zones, and estimates of ground water travel times in an unconfined ground water system of an outer coastal plain watershed on the Delmarva Peninsula, Virginia. By coupling recharge and discharge zones within the watershed, flowpath analysis can provide a method to locate and implement specific management strategies within a watershed to reduce ground water nitrogen loading to surface water. A monitoring well network was installed in Eyreville Creek watershed, a first-order creek, to determine hydraulic conductivities and spatial and temporal variations in hydraulic heads for use in model calibration. Ground water flow patterns indicated the convergence of flow along the four surface water features of the watershed; primary discharge areas were in the noontide portions of the watershed. Ground water recharge zones corresponded to the surface water features with minimal development of a regional ground water system. Predicted ground water velocities varied between 〈 0.01 to 0.24 m/day, with elevated values associated with discharge areas and areas of convergence along surface water features. Some ground water residence times exceeded 100 years, although average residence times ranged between 16 and 21 years; approximately 95% of the ground water resource would reflect land use activities within the last 50 years.