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USGS1982

Map projections used by the U.S. Geological Survey

After decades of using only one map projection, the Polyconic, for its mapping program, the U.S. Geological Survey (USGS) now uses sixteen of the more comnon map projections for its published maps. For larger scale maps, including topographic quadrangles and the State Base Map Series, conformal projections such as the Transverse Mercator and the Lambert Conformal Conic are used. On these, the shapes of small areas are shown correctly, but scale is correct only along one or two lines. Equal-area projections, especially the Albers Equal-Area Conic, and equidistant projections which have correct scale along many lines appear in the National Atlas. Other projections, such as the Miller Cylindrical and the Van der Grinten, are chosen occasionally for convenience, sometimes making use of existing base maps prepared by others. Some projections treat the Earth only as a sphere, others as either ellipsoid or sphere. The USGS has also conceived and designed several new projections, icluding the Space Oblique Mercator, the first map projection designed to permit mapping of the Earth continuously from a satellite with low distortion. The mapping of extraterrestrial bodies has resulted in the use of standard projections in completely new settings. With increased computerization, it is important to realize that rectangular coordinates for all these projections may be mathematically calculated with formulas which would have seemed too complicated in the past, but which now may be programed routinely, if clearly delineated with numerical examples. A discussion of appearance, usage, and history is given together with both forward and inverse equations for each projection involved.

Bulletin↗

USGS2022

Absolute accuracy assessment of lidar point cloud using amorphous objects

The accuracy assessment of airborne lidar point cloud typically estimates vertical accuracy by computing RMSEz (root mean square error of the z coordinate) from ground check points (GCPs). Due to the low point density of the airborne lidar point cloud, there is often not enough accurate semantic context to find an accurate conjugate point. To advance the accuracy assessment in full three-dimensional (3D) context, geometric features, such as the three-plane intersection point or two-line intersection point, are often used. Although the point density is still low, geometric features are mathematically modeled from many points. Thus, geometric features provide a robust determination of the intersection point, and the point is considered as a GCP. When no regular built objects are available, we describe the process of utilizing features of irregular shape called amorphous natural objects, such as a tree or a rock. When scanned to a high-density point cloud, an amorphous natural object can be used as ground truth reference data to estimate 3D georeferencing errors of the airborne lidar point cloud. The algorithm to estimate 3D accuracy is the optimization that minimizes the sum of the distance between the airborne lidar points to the ground scanned data. The search volume partitioning was the most important procedure to improve the computational efficiency. We also performed an extensive study to address the external uncertainty associated with the amorphous object method. We describe an accuracy assessment using amorphous objects (108 trees) spread over the project area. The accuracy results for ∆ x , ∆ y , and ∆ z obtained using the amorphous object method were 3.1 cm, 3.6 cm, and 1.7 cm RMSE, along with a mean error of 0.1 cm, 0.1 cm, and 4.5 cm, respectively, satisfying the accuracy requirement of U.S. Geological Survey lidar base specification. This approach shows strong promise as an alternative to geometric feature methods when artificial targets are scarce. The relative convenience and advantages of using amorphous targets, along with its good performance shown here, make this amorphous object method a practical way to perform 3D accuracy assessment.

Remote Sensing↗

USGS2013

Whole-coal versus ash basis in coal geochemistry: a mathematical approach to consistent interpretations

Several standard methods require coal to be ashed prior to geochemical analysis. Researchers, however, are commonly interested in the compositional nature of the whole-coal, not its ash. Coal geochemical data for any given sample can, therefore, be reported in the ash basis on which it is analyzed or the whole-coal basis to which the ash basis data are back calculated. Basic univariate (mean, variance, distribution, etc.) and bivariate (correlation coefficients, etc.) measures of the same suite of samples can be very different depending which reporting basis the researcher uses. These differences are not real, but an artifact resulting from the compositional nature of most geochemical data. The technical term for this artifact is subcompositional incoherence. Since compositional data are forced to a constant sum, such as 100% or 1,000,000 ppm, they possess curvilinear properties which make the Euclidean principles on which most statistical tests rely inappropriate, leading to erroneous results. Applying the isometric logratio (ilr) transformation to compositional data allows them to be represented in Euclidean space and evaluated using traditional tests without fear of producing mathematically inconsistent results. When applied to coal geochemical data, the issues related to differences between the two reporting bases are resolved as demonstrated in this paper using major oxide and trace metal data from the Pennsylvanian-age Pond Creek coal of eastern Kentucky, USA. Following ilr transformation, univariate statistics, such as mean and variance, still differ between the ash basis and whole-coal basis, but in predictable and calculated manners. Further, the stability between two different components, a bivariate measure, is identical, regardless of the reporting basis. The application of ilr transformations addresses both the erroneous results of Euclidean-based measurements on compositional data as well as the inconsistencies observed on coal geochemical data reported on different bases.

International Journal of Coal Geology↗

USGS2011

Are there pre-Quaternary geological analogues for a future greenhouse warming?

Given the inherent uncertainties in predicting how climate and environments will respond to anthropogenic emissions of greenhouse gases, it would be beneficial to society if science could identify geological analogues to the human race’s current grand climate experiment . This has been a focus of the geological and palaeoclimate communities over the last 30 years, with many scientific papers claiming that intervals in Earth history can be used as an analogue for future climate change. Using a coupled ocean–atmosphere modelling approach, we test this assertion for the most probable pre-Quaternary candidates of the last 100 million years: the Mid- and Late Cretaceous, the Palaeocene–Eocene Thermal Maximum (PETM), the Early Eocene, as well as warm intervals within the Miocene and Pliocene epochs. These intervals fail as true direct analogues since they either represent equilibrium climate states to a long-term CO 2 forcing—whereas anthropogenic emissions of greenhouse gases provide a progressive (transient) forcing on climate—or the sensitivity of the climate system itself to CO 2 was different. While no close geological analogue exists, past warm intervals in Earth history provide a unique opportunity to investigate processes that operated during warm (high CO 2 ) climate states. Palaeoclimate and environmental reconstruction/modelling are facilitating the assessment and calculation of the response of global temperatures to increasing CO 2 concentrations in the longer term (multiple centuries); this is now referred to as the Earth System Sensitivity, which is critical in identifying CO 2 thresholds in the atmosphere that must not be crossed to avoid dangerous levels of climate change in the long term. Palaeoclimatology also provides a unique and independent way to evaluate the qualities of climate and Earth system models used to predict future climate.

Philosophical Transactions of the Royal Society A:↗

USGS2002

Abstracts for the symposium on the application of neural networks to the earth sciences

Artificial neural networks are a group of mathematical methods that attempt to mimic some of the processes in the human mind. Although the foundations for these ideas were laid as early as 1943 (McCulloch and Pitts, 1943), it wasn't until 1986 (Rumelhart and McClelland, 1986; Masters, 1995) that applications to practical problems became possible. It is the acknowledged superiority of the human mind at recognizing patterns that the artificial neural networks are trying to imitate with their interconnected neurons. Interconnections used in the methods that have been developed allow robust learning. Capabilities of neural networks fall into three kinds of applications: (1) function fitting or prediction, (2) noise reduction or pattern recognition, and (3) classification or placing into types. Because of these capabilities and the powerful abilities of artificial neural networks, there have been increasing applications of these methods in the earth sciences. The abstracts in this document represent excellent samples of the range of applications. Talks associated with the abstracts were presented at the Symposium on the Application of Neural Networks to the Earth Sciences: Seventh International Symposium on Mineral Exploration (ISME–02), held August 20–21, 2002, at NASA Moffett Field, Mountain View, California. This symposium was sponsored by the Mining and Materials Processing Institute of Japan (MMIJ), the U.S. Geological Survey, the Circum-Pacific Council, and NASA. The ISME symposia have been held every two years in order to bring together scientists actively working on diverse quantitative methods applied to the earth sciences. Although the title, International Symposium on Mineral Exploration, suggests exclusive focus on mineral exploration, interests and presentations have always been wide-ranging—abstracts presented here are no exception.

Open-File Report↗

USGS2013

Fort Collins Science Center Ecosystem Dynamics branch--interdisciplinary research for addressing complex natural resource issues across landscapes and time

The Ecosystem Dynamics Branch of the Fort Collins Science Center offers an interdisciplinary team of talented and creative scientists with expertise in biology, botany, ecology, geology, biogeochemistry, physical sciences, geographic information systems, and remote-sensing, for tackling complex questions about natural resources. As demand for natural resources increases, the issues facing natural resource managers, planners, policy makers, industry, and private landowners are increasing in spatial and temporal scope, often involving entire regions, multiple jurisdictions, and long timeframes. Needs for addressing these issues include (1) a better understanding of biotic and abiotic ecosystem components and their complex interactions; (2) the ability to easily monitor, assess, and visualize the spatially complex movements of animals, plants, water, and elements across highly variable landscapes; and (3) the techniques for accurately predicting both immediate and long-term responses of system components to natural and human-caused change. The overall objectives of our research are to provide the knowledge, tools, and techniques needed by the U.S. Department of the Interior, state agencies, and other stakeholders in their endeavors to meet the demand for natural resources while conserving biodiversity and ecosystem services. Ecosystem Dynamics scientists use field and laboratory research, data assimilation, and ecological modeling to understand ecosystem patterns, trends, and mechanistic processes. This information is used to predict the outcomes of changes imposed on species, habitats, landscapes, and climate across spatiotemporal scales. The products we develop include conceptual models to illustrate system structure and processes; regional baseline and integrated assessments; predictive spatial and mathematical models; literature syntheses; and frameworks or protocols for improved ecosystem monitoring, adaptive management, and program evaluation. The descriptions in this fact sheet provide snapshots of our three research emphases, followed by descriptions of select current projects.

Fact Sheet↗

USGS2004

Water-quality data from 2002 to 2003 and analysis of data gaps for development of total maximum daily loads in the Lower Klamath River Basin, California

The U.S. Geological Survey (USGS) collected water-quality data during 2002 and 2003 in the Lower Klamath River Basin, in northern California, to support studies of river conditions as they pertain to the viability of Chinook and Coho salmon and endangered suckers. To address the data needs of the North Coast Regional Water Quality Control Board for the development of Total Maximum Daily Loads (TMDLs), water temperature, dissolved oxygen, specific conductance, and pH were continuously monitored at sites on the Klamath, Trinity, Shasta, and Lost Rivers. Water-quality samples were collected and analyzed for selected nutrients, organic carbon, chlorophyll-a, pheophytin-a, and trace elements. Sediment oxygen demand was measured on the Shasta River. Results of analysis of the data collected were used to identify locations in the Lower Klamath River Basin and periods of time during 2002 and 2003 when river conditions were more likely to be detrimental to salmonid or sucker health because of occasional high water temperatures, low dissolved oxygen, and conditions that supported abundant populations of algae and aquatic plants. The results were also used to assess gaps in data by furthering the development of the conceptual model of water flow and quality in the Lower Klamath River Basin using available data and the current understanding of processes that affect water quality and by assessing needs for the develoment of mathematical models of the system. The most notable gap in information for the study area is in sufficient knowledge about the occurrence and productivity of algal communities. Other gaps in data include vertical water-quality profiles for the reservoirs in the study area, and in an adequate understanding of the chemical oxygen demands and the sediment oxygen demands in the rivers and of the influence of riparian shading on the rivers. Several mathematical models are discussed in this report for use in characterizing the river systems in the study area; also discussed are the specific data needed for the models, and the spatial and temporal data available as boundary conditions. The models will be useful for the future development of TMDLs for temperature, nutrients, and dissolved oxygen and for assessing the role of natural and anthropogenic sources of heat, oxygen-producing and -consuming substances, and nutrients in the Klamath, Shasta, and Lost Rivers.

Scientific Investigations Report↗

USGS2009

Rebuttal of "Polar bear population forecasts: a public-policy forecasting audit"

Observed declines in the Arctic sea ice have resulted in a variety of negative effects on polar bears ( Ursus maritimus ). Projections for additional future declines in sea ice resulted in a proposal to list polar bears as a threatened species under the United States Endangered Species Act. To provide information for the Department of the Interior's listing-decision process, the US Geological Survey (USGS) produced a series of nine research reports evaluating the present and future status of polar bears throughout their range. In response, Armstrong et al. [Armstrong, J. S., K. C. Green, W. Soon. 2008. Polar bear population forecasts: A public-policy forecasting audit. Interfaces 38 (5) 382–405], which we will refer to as AGS, performed an audit of two of these nine reports. AGS claimed that the general circulation models upon which the USGS reports relied were not valid forecasting tools, that USGS researchers were not objective or lacked independence from policy decisions, that they did not utilize all available information in constructing their forecasts, and that they violated numerous principles of forecasting espoused by AGS. AGS (p. 382) concluded that the two USGS reports were "unscientific and inconsequential to decision makers." We evaluate the AGS audit and show how AGS are mistaken or misleading on every claim. We provide evidence that general circulation models are useful in forecasting future climate conditions and that corporate and government leaders are relying on these models to do so. We clarify the strict independence of the USGS from the listing decision. We show that the allegations of failure to follow the principles of forecasting espoused by AGS are either incorrect or are based on misconceptions about the Arctic environment, polar bear biology, or statistical and mathematical methods. We conclude by showing that the AGS principles of forecasting are too ambiguous and subjective to be used as a reliable basis for auditing scientific investigations. In summary, we show that the AGS audit offers no valid criticism of the USGS conclusion that global warming poses a serious threat to the future welfare of polar bears and that it only serves to distract from reasoned public-policy debate.

Interfaces↗

USGS1983

Clay mineral formation and transformation in rocks and soils

Three mechanisms for clay mineral formation (inheritance, neoformation, and transformation) operating in three geological environments (weathering, sedimentary, and diagenetic-hydrothermal) yield nine possibilities for the origin of clay minerals in nature. Several of these possibilities are discussed in terms of the rock cycle. The mineralogy of clays neoformed in the weathering environment is a function of solution chemistry, with the most dilute solutions favoring formation of the least soluble clays. After erosion and transportation, these clays may be deposited on the ocean floor in a lateral sequence that depends on floccule size. Clays undergo little reaction in the ocean, except for ion exchange and the neoformation of smectite; therefore, most clays found on the ocean floor are inherited from adjacent continents. Upon burial and heating, however, dioctahedral smectite reacts in the diagenetic environment to yield mixed-layer illite-smectite, and finally illite. With uplift and weathering, the cycle begins again. Refs.

Philosophical Transactions of the Royal Society A:↗

USGS2023

Generalized additive model estimation of no-flow fractions and L-moments to support flow-duration curve quantile estimation using selected probability distributions for bay and estuary restoration in the Gulf States

Censored and uncensored generalized additive models (GAMs) were developed using streamflow data from 941 U.S. Geological Survey streamflow-gaging stations (streamgages) to predict decadal statistics of daily streamflow for streams draining to the Gulf of Mexico. The modeled decadal statistics comprise no-flow fractions and L-moments of logarithms of nonzero streamflow for six decades (1950–2009). These statistics represent metrics of decadal flow-duration curves (dFDCs) derived from about 10 million daily mean streamflows. The L-moments comprise the mean, coefficient of L-variation, and the third through fifth L-moment ratios. The GAMs were fit to the statistics from 941 streamgages and 2,750 streamgage-decades by using watershed properties such as basin area and slope, decadal precipitation and temperature, and decadal values of flood storage and urban development percentages. The GAMs then estimated decadal statistics for 9,220 prediction locations (stream reaches) coincident with outlets of level-12 hydrologic unit codes. Both entire dataset (whole model) and leave-one-watershed-out model results are reported. No-flow fractions are censored data, and Tobit extensions to GAMs were used to model ephemeral streamflow conditions. Conversely, uncensored GAMs were used for estimation of the L-moments. The GAMs are shown, by coverage probabilities, to construct reliable 95-percent prediction limits. An example shows how no-flow fractions and L-moments may be used to approximate dFDCs by using selected probability distributions (mathematical formulas) including the asymmetric exponential power, generalized normal, and kappa distributions.

Alabama, Arkansas, Florida, Georgia, Kentucky, Lou↗

USGS1985

A constitutive equation for mass-movement behavior

A phenomenological constitutive equation can serve as a basis for modeling and classifying mass-movement processes. The equation is derived using the principles of continuum mechanics and several simplifying assumptions about mass-movement behavior. These assumptions represent idealizations of field behavior, but they appear highly justifiable in light of the geomorphological insight that can be gained through modeling application of a mathematically tractable constitutive equation. The equation represents coupled pressure-dependent plastic yield and nonlinear viscous flow deformation components. The plastic yield component is a generalization of the Coulomb criterion to three-dimensional stress states, and the effect of pore-water pressures is accounted for by treating normal stresses as effective stresses. The nonlinear viscous flow component is a dimensionally homogeneous form of a three-dimensional power-law equation. Straightforward laboratory and field experiments can be used to estimate all plastic and viscous parameters in the constitutive equation. Reduction of the three-dimensional constitutive equation to two-and one-dimensional forms shows that it embodies, as special cases, many other constitutive models for mass movement. These include models of creeping, slumping, sliding, and flowing types of deformation. The equation may, therefore, serve as a conceptual basis for rheological classification of diverse mass-movement phenomena.

Journal of Geology↗

USGS1977

Chemical variability in the Lakeview Mountains pluton, southern California batholith: A comparison of the methods of correspondence analysis and extended Q-mode factor analysis

An extended method of Q -mode factor analysis that has been described previously offers a number of important advantages over conventional Q -mode factor analysis and correspondence analysis when applied to compositional data. Among these are the ability to compute the compositions, in the original units of the data, represented by the reference axes. The only special requirement of the data is that the values for each observation sum to a constant. Mathematically derived reference axes, such as the principal-components and varimax axes, commonly represent compositions that are partly negative. Even where no negative values are present, these compositions are comparatively difficult to interpret in petrologic terms and impossible or inappropriate to include in petrogenetic models. A model has been developed for the Lakeview Mountains pluton which employs vectors representing the compositions of melanocratic schlieren, leucocratic schlieren, and inclusions as the reference axes. When the effect of the inclusions is removed, the compositional zoning in the pluton is like that found in otherwise similar plutons in the Sierra Nevada batholith. The genetic implication of the model is that the inclusions were separated from the magma at least in its marginal parts. In the central part of the pluton, the inclusions were either separated to a lesser extent than in the marginal parts, or were reincorporated into the magma.

California↗

USGS2013

The PRISM (Pliocene Palaeoclimate) reconstruction: Time for a paradigm shift

Global palaeoclimate reconstructions have been invaluable to our understanding of the causes and effects of climate change, but single-temperature representations of the oceanic mixed layer for data–model comparisons are outdated, and the time for a paradigm shift in marine palaeoclimate reconstruction is overdue. The new paradigm in marine palaeoclimate reconstruction stems the loss of valuable climate information and instead presents a holistic and nuanced interpretation of multi-dimensional oceanographic processes and responses. A wealth of environmental information is hidden within the US Geological Survey's P liocene R esearch, I nterpretation and S ynoptic M apping (PRISM) marine palaeoclimate reconstruction, and we introduce here a plan to incorporate all valuable climate data into the next generation of PRISM products. Beyond the global approach and focus, we plan to incorporate regional climate dynamics with emphasis on processes, integrating multiple environmental proxies wherever available in order to better characterize the mixed layer, and developing a finer time slice within the Mid-Piacenzian Age of the Pliocene, complemented by underused proxies that offer snapshots into environmental conditions. The result will be a proxy-rich, temporally nested, process-oriented approach in a digital format - a relational database with geographic information system capabilities comprising a three-dimensional grid representing the surface layer, with a plethora of data in each cell.

Philosophical Transactions of the Royal Society A:↗

USGS2012

Documentation of the Surface-Water Routing (SWR1) Process for modeling surface-water flow with the U.S. Geological Survey Modular Ground-Water Model (MODFLOW-2005)

A flexible Surface-Water Routing (SWR1) Process that solves the continuity equation for one-dimensional and two-dimensional surface-water flow routing has been developed for the U.S. Geological Survey three-dimensional groundwater model, MODFLOW-2005. Simple level- and tilted-pool reservoir routing and a diffusive-wave approximation of the Saint-Venant equations have been implemented. Both methods can be implemented in the same model and the solution method can be simplified to represent constant-stage elements that are functionally equivalent to the standard MODFLOW River or Drain Package boundary conditions. A generic approach has been used to represent surface-water features (reaches) and allows implementation of a variety of geometric forms. One-dimensional geometric forms include rectangular, trapezoidal, and irregular cross section reaches to simulate one-dimensional surface-water features, such as canals and streams. Two-dimensional geometric forms include reaches defined using specified stage-volume-area-perimeter (SVAP) tables and reaches covering entire finite-difference grid cells to simulate two-dimensional surface-water features, such as wetlands and lakes. Specified SVAP tables can be used to represent reaches that are smaller than the finite-difference grid cell (for example, isolated lakes), or reaches that cannot be represented accurately using the defined top of the model. Specified lateral flows (which can represent point and distributed flows) and stage-dependent rainfall and evaporation can be applied to each reach. The SWR1 Process can be used with the MODFLOW Unsaturated Zone Flow (UZF1) Package to permit dynamic simulation of runoff from the land surface to specified reaches. Surface-water/groundwater interactions in the SWR1 Process are mathematically defined to be a function of the difference between simulated stages and groundwater levels, and the specific form of the reach conductance equation used in each reach. Conductance can be specified directly or calculated as a function of the simulated wetted perimeter and defined reach bed hydraulic properties, or as a weighted combination of both reach bed hydraulic properties and horizontal hydraulic conductivity. Each reach can be explicitly coupled to a single specific groundwater-model layer or coupled to multiple groundwater-model layers based on the reach geometry and groundwater-model layer elevations in the row and column containing the reach. Surface-water flow between reservoirs is simulated using control structures. Surface-water flow between reaches, simulated by the diffusive-wave approximation, can also be simulated using control structures. A variety of control structures have been included in the SWR1 Process and include (1) excess-volume structures, (2) uncontrolled-discharge structures, (3) pumps, (4) defined stage-discharge relations, (5) culverts, (6) fixed- or movable-crest weirs, and (7) fixed or operable gated spillways. Multiple control structures can be implemented in individual reaches and are treated as composite flow structures. Solution of the continuity equation at the reach-group scale (a single reach or a user-defined collection of individual reaches) is achieved using exact Newton methods with direct solution methods or exact and inexact Newton methods with Krylov sub-space methods. Newton methods have been used in the SWR1 Process because of their ability to solve nonlinear problems. Multiple SWR1 time steps can be simulated for each MODFLOW time step, and a simple adaptive time-step algorithm, based on user-specified rainfall, stage, flow, or convergence constraints, has been implemented to better resolve surface-water response. A simple linear- or sigmoid-depth scaling approach also has been implemented to account for increased bed roughness at small surface-water depths and to increase numerical stability. A line-search algorithm also has been included to improve the quality of the Newton-step upgrade vector, if possible. The SWR1 Process has been benchmarked against one- and two-dimensional numerical solutions from existing one- and two-dimensional numerical codes that solve the dynamic-wave approximation of the Saint-Venant equations. Two-dimensional solutions test the ability of the SWR1 Process to simulate the response of a surface-water system to (1) steady flow conditions for an inclined surface (solution of Manning's equation), and (2) transient inflow and rainfall for an inclined surface. The one-dimensional solution tests the ability of the SWR1 Process to simulate a looped network with multiple upstream inflows and several control structures. The SWR1 Process also has been compared to a level-pool reservoir solution. A synthetic test problem was developed to evaluate a number of different SWR1 solution options and simulate surface-water/groundwater interaction. The solution approach used in the SWR1 Process may not be applicable for all surface-water/groundwater problems. The SWR1 Process is best suited for modeling long-term changes (days to years) in surface-water and groundwater flow. Use of the SWR1 Process is not recommended for modeling the transient exchange of water between streams and aquifers when local and convective acceleration and other secondary effects (for example, wind and Coriolis forces) are substantial. Dam break evaluations and two-dimensional evaluations of spatially extensive domains are examples where acceleration terms and secondary effects would be significant, respectively.

Techniques and Methods↗

USGS1956

Ground water in northeastern Louisville, Kentucky with reference to induced infiltration

In cooperation with the city of Louisville, Ky., the U. S. Geological Survey made a detailed investigation during the period February 1945 to March 1947 of the ground-water resources of a 3-square-mile area along the Ohio River north-east of Louisville. Test drilling shows that the principal aquifer consists of about 80 feet of glacial-outwash sands and gravels lying in an old river channel which was cut into rocks of Ordovician, Silurian, and Devonian age. The total ground-water storage in the area is estimated as 7 billion gallons. The ground-water levels are affected by changes in river elevation, by rainfall, and by the effects of pumping in the downtown part of Louisville 3 miles to the southwest. In the northeastern part of the area the flow of ground water, as defined by contour maps, is toward the river, and in the southwestern part of the area it is from the river toward the downtown area of overpumping. Ground water in the area has an average temperature of 56° F. The water, which is moderately hard, is suitable for domestic and industrial uses. Analysis of a pumping test made during the investigation proves that infiltration supplies can be developed. Studies to determine the degree of connection between the river and aquifer were made on the basis of chemical analyses, sections showing temperature distribution in the aquifer during the pumping test, shapes of water-level profiles in the test area, and shapes of time-drawdown curves for a number of observation wells. Quantitative studies to evaluate the hydrologic constants of the aquifer were made by both graphical and mathematical methods. The transmissibility was determined as 121,000 gpd/ft in the test area; the distance to the line source, 400 feet; and the coefficient of storage, 0.0003. A comparison of river-level fluctuations and water-level fluctuations in observation wells shows that conditions along the 6.4-mile reach of river are not greatly different from those at the site of the pumping test. It is estimated that under adverse temperature and river-stage conditions infiltration supplies could be developed to the extent of 280 million gpd in the entire 6.4-mile reach investigated; at average river-water temperature (59° F) about 400 million gpd could be developed. Diagrams were drawn showing the estimated yield of wells of different radii, at various distances from the river, and at various spacings. In making the computations allowance was made for screen losses, dewatering of the aquifer, partial penetration of wells, location wells, eccentricity of large wells, and interference among wells.

Kentucky↗

USGS2010

Simulating the volatilization of solvents in unsaturated soils during laboratory and field infiltration experiments

This paper describes laboratory and field experiments which were conducted to study the dynamics of trichloroethylene (TCE) as it volatilized from contaminated groundwater and diffused in the presence of infiltrating water through the unsaturated soil zone to the land surface. The field experiments were conducted at the Picatinny Arsenal, which is part of the United States Geological Survey Toxic Substances Hydrology Program. In both laboratory and field settings the gas and water phase concentrations of TCE were not in equilibrium during infiltration. Gas-water mass transfer rate constants were calibrated to the experimental data using a model in which the water phase was treated as two phases: a mobile water phase and an immobile water phase. The mass transfer limitations of a volatile organic compound between the gas and liquid phases were described explicitly in the model. In the laboratory experiment the porous medium was nonsorbing, and water infiltration rates ranged from 0.076 to 0.28 cm h −1 . In the field experiment the water infiltration rate was 0.34 cm h −1 , and sorption onto the soil matrix was significant. The laboratory-calibrated gas-water mass transfer rate constant is 3.3×10 −4 h −1 for an infiltration rate of 0.076 cm h −1 and 1.4×10 −3 h −1 for an infiltration rate of 0.28 cm h −1 . The overall mass transfer rate coefficients, incorporating the contribution of mass transfer between mobile and immobile water phases and the variation of interfacial area with moisture content, range from 3×10 −4 h −1 to 1×10 −2 h −1 . A power law model relates the gas-water mass transfer rate constant to the infiltration rate and the fraction of the water phase which is mobile. It was found that the results from the laboratory experiments could not be extrapolated to the field. In order to simulate the field experiment the very slow desorption of TCE from the soil matrix was incorporated into the mathematical model. When desorption from the soil matrix was added to the model, the calibrated gas-water mass transfer rate constant is 2 orders of magnitude lower than that predicted using the power law model developed for the nonsorbing laboratory soil.

Water Resources Research↗

USGS1971

The effect of salinity on the maximum thermal gradient of a hydrothermal system at hydrostatic pressure

The effect of salinity on the temperature-depth relations of a brine of constant composition, enclosed in a vein system, but freely connected to the surface, and everywhere at the boiling point for the hydrostatic head, was calculated by using a mathematical model. The Na-Ca-K-Cl brines which are found in thermal springs and in fluid inclusions in ore minerals were approximated by the available data for vapor-saturated NaCl-H 2 O solutions. In general, the results are similar to those calculated by D. E. White in 1968 for H 2 O, except that the gradients are steeper because of the increase in density and the decrease in vapor pressure caused by the dissolved salt. As a practical rule, the depth to an isotherm in a 5, 10, 15, 20, and 25 wt percent NaCl brine system is, respectively, 92, 84, 77, 70, and 63 percent (+ or -2 percent) of the depth to the same isotherm in an H 2 O system. From the data presented, the minimum depth to the growth site of crystals containing fluid inclusions which indicate boiling of the brine can be estimated. Among other applications, these results are useful toward the understanding of the behavior of brines in geothermal areas which may or may not contain compositional stratification.

Economic Geology↗

USGS2012

Migration rates and formation injectivity to determine containment time scales of sequestered carbon dioxide

Supercritical carbon dioxide exhibits highly variable behavior over a range of reservoir pressure and temperature conditions. Because geologic sequestration of supercritical carbon dioxide is targeted for subsurface injection and containment at depths ranging from approximately 3,000 to 13,000 feet, the investigation into the physical properties of this fluid can be restricted to the pressure and temperature conditions likely encountered in the sedimentary strata within this depth interval. A petrophysical based approach was developed to study the widest range of formation properties potentially encountered in sedimentary strata. Fractional porosities were varied from 5 to 95 percent, in 5-percent increments, and permeability values were varied over thirteen orders of magnitude, from 10.0 darcys down to 1.0 picodarcy. Fluid-flow modeling incorporated two constitutive equations from fluid dynamics: hydraulic diffusivity for near-surface applications, and Darcy's Law for deeper formations exhibiting higher pressure gradients. Based on the flow modeling results, first-order approximations of carbon dioxide lateral migration rates were determined. These first-order approximations enable the establishment of a permeability classification system for dividing the subsurface into flow units that provide short, moderate, and long-term containment of carbon dioxide. These results enable a probabilistic determination of how fluids will enter and be contained in a subsurface storage formation, which is a vital step in the calculation of the carbon dioxide storage capacity of a reservoir. Additionally, this research establishes a methodology to calculate the injectivity of a target formation. Because injectivity describes the pressure increase due to the introduction of fluids into a formation, the relevant application of injectivity is to determine the pressure increase, due to an injection volume and flow rate, that will induce fractures in the reservoir rocks. This quantity is defined mathematically as the maximum pressure differential between the hydrostatic gradient and the fracture gradient of the target formation. Injectivity is mathematically related to the maximum pressure differential of the formation, and can be used to determine the upper limit for the pressure increase that an injection target can withstand before fracturing.

Open-File Report↗