bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Generalized Approach for the Interpretation of Geophysical Well Logs in Ground‐Water Studies—Theory and Application
Authors: Paillet F. L. , Crowder R. E. 
Published: August 2005

AbstractQuantitative analysis of geophysical logs in ground‐water studies often involves at least as broad a range of applications and variation in lithology as is typically encountered in petroleum exploration, making such logs difficult to calibrate and complicating inversion problem formulation. At the same time, data inversion and analysis depend on inversion model formulation and refinement, so that log interpretation cannot be deferred to a geophysical log specialist unless active involvement with interpretation can be maintained by such an expert over the lifetime of the project. We propose a generalized log‐interpretation procedure designed to guide hydrogeologists in the interpretation of geophysical logs, and in the integration of log data into ground‐water models that may be systematically refined and improved in an iterative way. The procedure is designed to maximize the effective use of three primary contributions from geophysical logs: (1) The continuous depth scale of the measurements along the well bore; (2) The in situ measurement of lithologic properties and the correlation with hydraulic properties of the formations over a finite sample volume; and (3) Multiple independent measurements that can potentially be inverted for multiple physical or hydraulic properties of interest. The approach is formulated in the context of geophysical inversion theory, and is designed to be interfaced with surface geophysical soundings and conventional hydraulic testing. The step‐by‐step procedures given in our generalized interpretation and inversion technique are based on both qualitative analysis designed to assist formulation of the interpretation model, and quantitative analysis used to assign numerical values to model parameters. The approach bases a decision as to whether quantitative inversion is statistically warranted by formulating an over‐determined inversion. If no such inversion is consistent with the inversion model, quantitative inversion is judged not possible with the given data set. Additional statistical criteria such as the statistical significance of regressions are used to guide the subsequent calibration of geophysical data in terms of hydraulic variables in those situations where quantitative data inversion is considered appropriate.
Probabilistic Assessment of Ground‐Water Contamination: 1. Geostatistical Framework
Authors: Rautman Christopher A. , Istok Jonathan D. 
Published: August 2005

AbstractCharacterizing the extent and severity of ground‐water contamination at waste sites is expensive and time‐consuming. A probabilistic approach, based on the acceptance of uncertainty and a finite probability of making classification errors (contaminated relative to a regulatory threshold vs. uncontaminated), is presented as an alternative to traditional site characterization methodology. The approach utilizes geostatistical techniques to identify and model the spatial continuity of contamination at a site (variography) and to develop alternate plausible simulations of contamination fields (conditional simulation). Probabilistic summaries of many simulations provide tools for (a) estimating the range of plausible contaminant concentrations at unsampled locations, (b) identifying the locations of boundaries between contaminated and uncontaminated portions of the site and the degree of certainty in those locations, and (c) estimating the range of plausible values for total contaminant mass. The first paper in the series presents the geostatistical framework and illustrates the approach using synthetic data for a hypothetical site. The second paper presents an application of the proposed methodology to the probabilistic assessment of ground‐water contamination at a site involving ground‐water contamination by nitrate and herbicide in a shallow, unconfined alluvial aquifer in an agricultural area in eastern Oregon.
Macroscopic Models for Predicting Changes in Saturated Porous Media Properties Caused by Microbial Growth
Authors: Clement T. P. , Hooker B. S. , Skeen R. S. 
Published: August 2005

AbstractAnalytical equations are developed to model changes in porosity, specific surface area, and permeability caused by biomass accumulation in porous media. The proposed equations do not assume any specific pattern for microbial growth but instead are based on macroscopic estimates of average biomass concentrations. For porous media with a pore‐size distribution index value (λ) equal to 3, the macroscopic model predictions of porosity, specific surface area, and permeability changes are in exact agreement with biofilm‐model predictions. At other values of λ between 2 and 5, simulated porosity profiles are identical and relative specific surface area and permeability profiles show minor deviations. In comparison to biofilm‐based models, the macroscopic models are relatively simple to implement and are computationally more efficient. Simulations of biologically reactive flow in a one‐dimensional column show that the macroscopic and biofilm approach based transport codes predict almost identical porosity and permeability profiles. The macroscopic models are simple and useful tools for estimating changes in various porous media properties during bioremediation of contaminated aquifers.
Estimation of Spatial and Temporal Variability of Recharge Fluxes to an Alluvial Aquifer in a Fore Land Area by Water Chemistry and Isotopes
Authors: Guglielmi Y. , Mudry J. 
Published: August 2005

AbstractThe Var Valley (Southern France) is a typical setting in which alluvial water is situated in a fore land area. The alluvial aquifer is recharged by seepage from the intake area of the river Var and by subsurface infiltration from its fore land area.Chemical and isotopic tracing of both sources is well contrasted, in accordance with the very different geology and relief in the two places. 18O, silica, and sulphate contents were chosen to calculate percentages of recharge from the Var river and the embanking Pliocene pudding stones. Differences among recharge estimates, calculated from the three tracers are low, about 10%. Ground‐water areas where component contributions to recharge are maximum (over 70% for Var inflow and over 40% for pudding stone inflow) are considered feeding areas. Discharge of leakage from pudding stones was calculated by the use of the Hantush formula on the whole surface of these areas: 0.53 ± 0.2 m3/sec, which corresponds to 1/5 of the total water budget of the alluvial aquifer.Chemical surveying of alluvial water, during a water year, displays the constancy of ground‐water inflows over time, ranging from those when inflow surface water is nonexistent in the river Var during low‐water periods to those when it is massive in spate.Thus, during periods without influence from the river Var, the inflows from the embanking formation sustain discharge of alluvial water and influence its chemical makeup. Taking these results into account, the protection area of the lower river Var water resource must be enlarged to include a part of the intake area of the adjacent reservoirs.
Estimating Hydraulic Conductivities in an Alluvial Basin from Sediment Facies Models
Authors: McCloskey Thomas F. , Finnemore E. John 
Published: August 2005

AbstractIt is not uncommon that hydraulic conductivity data are sparse in an area, and that information about subsurface sediment distributions are even more sparse or of poor quality. It is therefore desirable to have rational ways to estimate conductivity distributions for ground‐water flow modeling. Interpretations of the geologic history of a fault‐bounded sedimentary basin in south Santa Clara County, California, were used to estimate variations in sediment distribution and resulting relative hydraulic conductivities. Spatial sediment distributions were interpreted from the dominant infilling processes, using standard sedimentary facies models for alluvial fans and fluvial deposition. These sedimentary facies were categorized into interpreted hydrogeologic facies, which were then compared with measured hydraulic conductivity data obtained from scattered aquifer pumping tests in the basin. The comparison suggests that sedimentary facies models can provide a good basis for estimating the distribution of relative hydraulic conductivity. Further, the comparison provides a procedure for estimating hydraulic conductivities in areas where no measured values are available. This procedure provides a better basis for estimating hydraulic conductivities than methods which do not consider sedimentary processes.
Evaluation of Hydraulic Conductivity of Carson County Well Field, Amarillo, Texas
Authors: Xiang Jiannan 
Published: August 2005

AbstractEnvironmental assessment, ground‐water management, and aquifer remediation designs rely on comprehension of the hydraulic parameters of aquifers. Because of the heterogeneity of most aquifers, a number of pumping tests are commonly required to provide a reasonable hydraulic parameter distribution. Data for 11 pumping tests, conducted at the Carson County well field, Amarillo, Texas in the 1950s to 1970s were analyzed by the Theis solution and the Cooper and Jacob solution to provide information for optimal ground‐water management. The unconfined aquifer at the well field consists of sands, sandstone, gravels, and clay. A delayed gravity response was observed in the drawdown curves from pumping tests conducted in the unconfined aquifer. Because the Theis solution and the Cooper and Jacob solution do not take this delayed response, or other unsaturated effect into account, these two solutions may overestimate hydraulic conductivity of an unconfined aquifer. Therefore, the Neuman solution which considers the delayed gravity response was used to estimate the hydraulic parameters using the software AQTESOLV (by Geraghty & Miller, Inc., 1990). This paper presents the results of a study of the unconfined aquifer at Carson County well field, Amarillo, Texas. The analysis shows that the results obtained by the Neuman method are more reasonable than those obtained by the Theis solution and the Cooper and Jacob solution. According to results from the Neuman solution, the hydraulic conductivity of the unconfined aquifer of Carson County well field varies from 2.55 to 5.97 × 10−5 m/s (weighted average hydraulic conductivity is 4.13 × 10−5 m/s). The small difference of the estimated hydraulic conductivity between wells shows that the unconfined aquifer under Carson County well field is relatively uniform. The effects of infinitesimal borehole assumption, accuracy of individual parameters, skin effects, and spatial distribution of hydraulic conductivity are discussed as well. It is also shown that benefits from obtaining accurate results should be weighted against budget requirements.
Hydrology and Geochemistry of Thermal Waters in the Upper Napa Valley, California
Authors: Murray Kent S. 
Published: August 2005

AbstractShallow low‐to‐moderate temperature geothermal waters are found in the upper part of the Napa Valley near the town of Calistoga, California. The geology of the upper Napa Valley is dominated by Jurassic to Cretaceous eugosynclinal Franciscan assemblage and the late Tertiary (Pliocene) Sonoma Volcanic rocks. Minor post‐Pliocene normal faulting is evident in the volcanic rocks north and southeast of the study area. The thermal waters which have a sodium chloride chemistry with elevated concentrations of chloride, boron, and fluoride, are attributed to fault‐controlled hydrothermal circulation. The cold waters are characterized as mixed‐cation bicarbonate type with high concentrations of calcium, magnesium, and iron. The geothermal aquifer is believed to be recharged by the upwelling of thermal water along a linear fault zone aligned with the topographic axis of the Napa Valley. Data from 140 domestic water wells were used to evaluate the chemical character of the geothermal resource and to construct maps of chloride and boron concentrations. These maps were subsequently used to locate the source of the deep thermal water and zones of cold and hot water mixing, and to develop a conceptual model of the geothermal system.
Indicator Geostatistical Analysis of Sand Interconnections Within a Till
Authors: Sminchak Joel R. , Dominic David F. , Ritzi Robert W. 
Published: August 2005

AbstractAt the Fernald Environmental Management Project (FEMP) site in southwestern Ohio, sand and gravel lenses within till provide potential pathways for the flow of contamination into the underlying aquifer. These high‐permeability lenses account for 22% of the volume of the till, have a complex arrangement, and are smaller in scale than the site. Even the relatively dense subsurface sampling program at the FEMP site is not adequate to determine facies interconnections with certainty. To delineate probable facies boundaries, a binary indicator random variable was used to represent the presence of high or low‐permeability sediment. The 800 available lithologic logs that penetrate the till were coded with the binary system at 2 ft (0.6 m) intervals yielding 15,829 observations. These data were used to compute the declustered mean of indicator values in horizontal intervals, giving an estimate of the proportion of high‐permeability sediment in each vertical zone. The areal correlation in specific zones was examined through indicator variograms, which had pronounced anisotropy. Three‐dimensional indicator point kriging was used to produce maps of the probability of existence of high‐permeability sediment. These maps were used in a preliminary analysis of sand body interconnectedness. Results indicate that portions of sand bodies are interconnected through the entire interval studied and that the areal extent of vertical interconnection is up to 1000 ft.
Origin of Subsurface Brines in the Sichuan Basin
Authors: Xun Zhou , Cijun Li , Xiumin Ju , Qiang Du , Lihong Tong 
Published: August 2005

AbstractSubsurface brines in the Sichuan Basin occur within sedimentary rocks ranging in age from Sinian to Cretaceous, especially within rocks of Triassic age. The chemical and isotopic compositions of the brines and general geological considerations suggest that the Sichuan Basin brines are derived from waters of different origin. Water in brines from Upper Cretaceous clastic reservoirs in Anren, and from basin margin aquifers of Lower Jurassic, Triassic, and Cambrian age are modern meteoric in origin. Salinity in these brines is from dissolution of salt‐bearing formations. Lower Jurassic and Upper Triassic clastic aquifers contain a mixture of meteoric water and brines from older rocks based on isotopic data. Brines in Middle and Lower Triassic carbonate aquifers originated from sea water and are residual brines left after evaporite precipitation. Brines from the Upper Sinian carbonate aquifer in Weiyuan originated from sea water mixed with magmatic waters.
Organic Carbon Dominated Trichloroethene Sorption in a Clay‐Rich Glacial Deposit
Authors: Allen‐King Richelle M. , McKay Larry D. , Trudell Mark R. 
Published: August 2005

AbstractThe relative contributions of organic carbon and mineral matter to trichloroethene (TCE) sorption were determined for a natural, clay‐rich till from Sarnia, Ont. using laboratory batch tests. Linear TCE sorption coefficients of the two till samples (approximataely 12 to 15 m depth) were 64.2 l/kg and 151 l/kg and the organic carbon contents (foc) were 0.68% and 1.95%, respectively. To ascertain the importance of sorption to mineral matter versus organic carbon, till samples were treated by baking. The foc was reduced by 44 to 90% in treated samples compared to natural samples. TCE sorption coefficients were also reduced to 0.48 to 4.64 l/kg in treated samples. Surface area measurements suggested that treating the till samples appeared to have little effect on the mineral matter. The results indicated that TCE sorption is dominated by the naturally occurring organic carbon. The organic carbon normalized sorption coefficients (Koc) for the natural (untreated) samples were 16 to 500 times greater than those typically reported for sediment and soil samples, indicating the more lipophilic character of the organic matter in the till. Koc estimates which accounted for the oxidation state of the organic carbon in the till assuming the carbon is primarily from Devonian‐age shale fragments resulted in values close to (within a factor of 2 to 5) those observed. Thus, both the nature and amount of organic carbon in the till play major roles in controlling the magnitude of TCE sorption in this clay‐rich deposit.
On the Strategy of Estimating Regional‐Scale Transmissivity Fields
Authors: Christensen Steen 
Published: August 2005

AbstractA case study of a leaky fluvioglacial aquifer concentrates on methods of estimating the zonated log10‐transmissivities of a regional‐scale ground‐water model covering 450 km2. Mainly three estimation methods are discussed: (a) kriging based on local measurements and predictions, (b) hydrologic inversion (i.e., nonlinear regression) based on head data, and (c) hydrologic inversion based on head data and on prior estimates from kriging. (a) Due to the shortage of data which is usual in heterogeneous aquifers, the present study questions the practical value of forming zonal kriging estimates from local data whenever estimates are to be used as an input to ground‐water models. In some parts of the homogeneous aquifers local data are sufficient to make such estimates, (b) In this study zonal hydrogeological parameters can be estimated by inversion based on head data. However, inaccuracies in head data may seriously damage the reliability of estimated parameters and, as a consequence, the ground‐water model, (c) Using zonal kriging estimates as prior information in the regression reduces the width of the confidence intervals of the parameters with prior information by up to 75%. The study indicates, however, that using prior information in the estimation of the hydrologic model parameters only minimally reduces the uncertainty of the predicted hydraulic heads.For this specific case, the results suggest that in order to parameterize and identify the parameters of the ground‐water model one should concentrate on qualitative mapping of the hydrogeology, on sampling accurate head data and on subsequent estimation of the zonal parameters by inversion (or manual calibration).
Verifying the Integrity of Annular and Back‐Filled Seals for Vadose‐Zone Monitoring Wells
Authors: Dunnivant Frank M. , Porro Indrek , Bishop Carolyn , Hubbell Joel , Giles John R. , Newman Meredith E. 
Published: August 2005

AbstractMonitoring the movement of contaminants throughout the vadose zone requires the use of wells and the credibility of a monitoring program depends on obtaining an adequate seal between the well casing and borehole wall. The credibility of monitoring well installation was evaluated during the Idaho National Engineering Laboratory's Large Scale Pumping and Infiltration Test. Wells were drilled in and around a 6.5 acre infiltration basin with an air rotary rig using a downhole hammer, cased with PVC or steel, and the annular space back‐filled with alternating layers of bentonite and sand. The purpose of completing the wells in this manner was to isolate fractured intervals (subvertical and subhorizontal interflow zones) in order to observe water movement during the infiltration test. Bentonite was used between sand intervals to prevent the borehole (or annular space) from serving as a conduit for vertical water flow or tracer migration. Neutron probes were used to confirm the presence and locations of each completion interval (sand or bentonite) by distinguishing differences in background‐water content of the back‐filling materials. Upon flooding of the infiltration basin with water containing radioactive tracers, water flow and tracer transport were monitored using neutron probes and an in situ, downhole gamma spectroscopy system, respectively. Results confirm that each well was installed correctly; water and tracers flowed through natural fractures in the subsurface and arrived at the monitoring sites located at sand completion zones. Significant water or tracer flow through the annular space between the well casing and borehole was not observed.
Distinguishing Natural Hydrocarbons from Anthropogenic Contamination in Ground Water
Authors: Lesage Suzanne , Xu Hao , Novakowski Kent S. 
Published: August 2005

AbstractDifferentiation between natural and anthropogenic sources of ground‐water contamination by petroleum hydrocarbons is necessary in areas where natural hydrocarbons may be present in the subsurface. Because of the similarity in composition between natural and refined petroleum, the use of statistical techniques to discern trends is required. In this study, both multivariate plotting techniques and principal component analysis were used to investigate the origin of hydrocarbons from a variety of study sites. Ground‐water and gas samples were collected from the Niagara Falls area and from three gasoline stations where leaking underground storage tanks had been found. Although soil gas surveys are used to indicate the presence of hydrocarbons, they were not useful in differentiating between natural and anthropogenic sources of contamination in ground water. Propane and pentene were found to be the most useful chemical parameters in discriminating between the natural and anthropogenic sources. These chemicals are not usually measured in investigations of ground‐water contamination, yet analysis can be conducted by most environmental laboratories using conventional methods.
Use of Solute Chemistry and Isotopes to Identify Sources of Ground‐Water Recharge in the Nile Aquifer System, Upper Egypt
Authors: Awad Mostafa A. , El Arabi Nahed E. , Hamza Mokhtar S. 
Published: August 2005

AbstractTwelve ground‐water samples were collected in the Nag Hammadi area, from Quaternary and Plio‐Pleistocene age aquifers. The isotopic data indicate that the main recharge source of the Quaternary aquifer is the recent River Nile water, which is isotopically enriched from evaporation in Lake Nasser. Sources of recharge to the Plio‐Pleistocene aquifer are: (1) Old Nile water depleted in isotope composition, which was trapped in the geological formation, characterized by low permeability and clay lenses prior to the construction of the Aswan High Dam; and (2) The leakage of palaeo water from the deep aquifer system through main faults which bisect the study area. The variation in the chemistry of ground water is thought to be related to mixing between the different water sources and leaching of fertilizers in the newly reclaimed areas in the desert fringes.
Ground‐Water Solute Transport with Hydrogeochemical Reactions
Authors: García‐Delgado Rafael A. , Koussis Antonis D. 
Published: August 2005

AbstractChemical contamination of ground water is typically associated with multicomponent solutions of reactive substances, the mobility of which is affected by their reactivity. In predicting geochemical transport, it is therefore important that the liquid and solid phase reactions be modeled, along with the flow‐controlled processes. This demanding task is typically carried out on powerful computers. Frequently, however, field data are available for a limited number of species, or, a small number of species suffices to characterize ground‐water quality. In such cases it is desirable to be able to model the transport on a widely available class of inexpensive computers. We report on the development of a 2‐D model for the transport of reactive species that runs efficiently on PCs. The model follows a modified one‐step procedure that adopts total (aqueous and adsorbed) concentrations and aqueous concentrations of components, and accounts for aqueous complexation and for competitive sorption via isotherms or selectivity coefficients. The use of principal directions of transport coordinates, dimensional splitting, and a specialized algorithm for handling advection‐dominated transport render it compact and efficient. Mass conservation is satisfied with high accuracy.