SEARCH · USGS Science

Results for “Nature Based Solutions”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources

USGS1997

Beryllium geochemistry in soils: Evaluation of 10Be/9Be ratios in authigenic minerals as a basis for age models

Soils contain a diverse and complex set of chemicals and minerals. Being an 'open system', both in the chemical and nuclear sense, soils have defied quantitative nuclear dating. However, based on the published studies of the cosmogenic atmospheric 10Be in soils, its relatively long half-life (1.5 Ma), and the fact that 10Be gets quickly incorporated in most soil minerals, this radionuclide appears to be potentially the most useful for soil dating. We therefore studied the natural variations in the specific activities of 10Be with respect to the isotope 9Be in mineral phases in eight profiles of diverse soils from temperate to tropical climatic regimes and evaluated the implications of the data for determining the time of formation of soil minerals, following an earlier suggestion [Lal et al., 1991. Development of cosmogenic nuclear methods for the study of soil erosion and formation rates. Current Sci. 61, 636-639.]. We find that the 10Be/9Be ratios in both bulk soils and in the authigenic mineral phases are confined within a narrower range than in 10Be concentrations. Also, the highest 10Be/9Be ratios in authigenic minerals are observed at the soil-rock interface as predicted by the model. We present model 10Be/9Be ages of the B-horizon and the corresponding soil formation rates for several soil profiles. The present study demonstrates that the 10Be/9Be ratios in the authigenic phases, e.g. clay and Fe-hydroxides, can indeed be used for obtaining useful model ages for soils younger than 10-15 Ma. However, the present work has to be pushed considerably further, to take into account more realistic age models in which, for instance, downward transport of 10Be and clays, and in-situ dissolution of clay minerals at depths, altering the 10Be/9Be ratios of the acidic solutions, are included. We show that in the case of younger soils (< 1 Ma) studied here, their 10Be inventories and 10Be/9Be ratios have been significantly disturbed possibly by mixing with transported soils. ?? 1997 Elsevier Science B.V.

Chemical Geology↗

USGS2020

The response of streams to changes in atmospheric deposition of sulfur and nitrogen in the Adirondack Mountains

Acidic deposition is the result of upwind sulfur (S) and nitrogen (N) emissions into the atmosphere from human activities. Environmental impacts from acidic deposition across forested landscapes include acidification of soil and drainage water, depletion of available soil nutrient bases, and impacts to and changes in forest and aquatic species composition and biodiversity. Acidic deposition can mobilize aluminum (Al) from soil-to-soil solution and subsequently to drainage water in forms that can be toxic to aquatic life. When exposed to decreasing levels of acidic deposition, which has been occurring in New York since the late 1970s, some soils and drainage waters have become gradually less acidic. Remaining questions relate to effects on stream resources, anticipated resource recovery under increasingly lower levels of deposition, and the levels of deposition (target loads, TLs) needed to reach a range of stream ecosystem recovery targets. Environmental scientists commonly estimate thresholds of air pollutant emissions and resulting atmospheric deposition at which adverse ecological effects are manifested. This analysis is often done using critical loads (CL) and/or TLs, using approaches that account for the spatial and temporal aspects of acidification and recovery. Exceedance represents the extent to which current levels of acidic deposition exceed the level expected to cause ecological harm. The research reported here is intended to help address S and N deposition TLs and ecosystem recovery of Adirondack streams, a resource that has been less thoroughly investigated than lakes. The overarching goal of this work is to highlight key considerations that will help inform decision-makers and ecosystem managers who are responsible for environmental policy in New York State and beyond. Salient aspects of stream TL modeling are discussed with an aim of informing not only scientists, but also policymakers, ecosystem managers, and nonscientists who are required to make decisions related to the effects of acidic deposition on natural ecosystems. Analyses reported herein quantify relations among chemical indicators and metrics of fish community health and biodiversity in streams of the Adirondack Park. This information is used to indicate levels of atmospheric deposition necessary to alleviate harmful effects on fish populations. Results of this investigation provide a framework that can be applied to better understand how modeled stream acid neutralizing capacity (ANC) values that are developed to support TL investigations can be adjusted to reflect high-flow ANC values that may be associated with toxic conditions. Since process models are often calibrated to a low-flow or average flow condition, the magnitude and spatial extent of TL exceedances increase substantially when episodic acidification is considered.

New York↗

USGS2004

Estimating hydraulic properties of the Floridan Aquifer System by analysis of earth-tide, ocean-tide, and barometric effects, Collier and Hendry Counties, Florida

Aquifers are subjected to mechanical stresses from natural, non-anthropogenic, processes such as pressure loading or mechanical forcing of the aquifer by ocean tides, earth tides, and pressure fluctuations in the atmosphere. The resulting head fluctuations are evident even in deep confined aquifers. The present study was conducted for the purpose of reviewing the research that has been done on the use of these phenomena for estimating the values of aquifer properties, and determining which of the analytical techniques might be useful for estimating hydraulic properties in the dissolved-carbonate hydrologic environment of southern Florida. Fifteen techniques are discussed in this report, of which four were applied. An analytical solution for head oscillations in a well near enough to the ocean to be influenced by ocean tides was applied to data from monitor zones in a well near Naples, Florida. The solution assumes a completely non-leaky confining unit of infinite extent. Resulting values of transmissivity are in general agreement with the results of aquifer performance tests performed by the South Florida Water Management District. There seems to be an inconsistency between results of the amplitude ratio analysis and independent estimates of loading efficiency. A more general analytical solution that takes leakage through the confining layer into account yielded estimates that were lower than those obtained using the non-leaky method, and closer to the South Florida Water Management District estimates. A numerical model with a cross-sectional grid design was applied to explore additional aspects of the problem. A relation between specific storage and the head oscillation observed in a well provided estimates of specific storage that were considered reasonable. Porosity estimates based on the specific storage estimates were consistent with values obtained from measurements on core samples. Methods are described for determining aquifer diffusivity by comparing the time-varying drawdown in an open well with periodic pressure-head oscillations in the aquifer, but the applicability of such methods might be limited in studies of the Floridan aquifer system.

Florida↗

USGS1998

Analytical methods, numerical modeling, and monitoring strategies for evaluating the effects of ground-water withdrawals on unconfined aquifers in the New Jersey Coastal Plain

Analytical and numerical solutions of ground-water withdrawals in the unconfined part of the Kirkwood-Cohansey aquifer system of the Coastal Plain of New Jersey were evaluated for their usefulness in predicting the area of influence of a pumped well and in determining hydraulic characteristics of an aquifer. Additionally, simulations of ground-water withdrawal using a finite-difference model provided information on the ways in which prudent well-location strategies can disperse the local effects of withdrawal over a larger part of an aquifer system. The design of a monitoring network that is sensitive to the ground-water hydraulics of streams and wetlands of the Coastal Plain of New Jersey also was considered for its utility in providing hydrologic data necessary to establish the baseline hydrologic conditions near wetlands and streams and in signaling when ground-water levels are being adversely affected by withdrawals elsewhere in the system. The application of methods based on the Theis analytical solution to ground-water flow in unconfined aquifers can lead to erroneous estimates of the size of the area of influence generated by ground-water withdrawals. Analysis oftime-drawdown data from an unconfined aquifer system are best evaluated by means of the Neuman solution, which accounts for the effects of gravity drainage; however, the pumped well must be far enough from streams so that ground water is not drawn from nearby streams. Time-drawdown data from a test well in Winslow County, N.J., were analyzed by means of the Neuman solution. Results indicate that the aquifer has a relatively high vertical to horizontal anisotropy of 1:198, and a specific yield of 0.028, an indication that the area of influence of a pumped well at the test site would be relatively large. Results from a finite-difference ground-water-flow model of the northeastern part of the Mullica River Basin near Chesilhurst, N.J., show that the area influenced by a long-term withdrawal is best estimated from a steady state ground-water-flow analysis that includes the effects of average areal recharge. Withdrawal simulations indicate an order-of-magnitude difference between the size of the area of influence generated from a 3-day (72 hour) withdrawal and the size of the area produced under steady-state conditions. An aquifer characterized by a low specific yield will cause the area of influence to extend farther away from the pumped well. The contributing area of flow to the pumped well includes areas on the water table that would, under natural conditions, be incorporated into the contributing areas of flow to streams. Ground water that is drawn to a pumped well is diverted from nearby streams; the withdrawal decreases the size of the contributing areas of flow to streams by an amount equal to the contributing area of flow to the well. Withdrawals made from a well close to a stream divert ground water that would, under natural conditions, flow to the stream. The diverted ground water causes the area of influence of the well to be smaller than it would if the well were far from the stream. Water-table declines caused by withdrawals near streams are, to some degree, mitigated by ground-water diversion from streams. However, the withdrawals can significantly reduce ground-water seepage to nearby streams, especially along stream reaches and wetlands close to the well. Alternatively, these effects can be dispersed over a large part of the aquifer if wells are located on surface-water divides. Measurements of seasonal water-level fluctuations in the Mullica River Basin indicate that the greatest fluctuations in water levels are found in upland areas, where the average fluctuation is 3.4 feet. Fluctuations in hydraulic head in the wetland areas averages 1.3 feet. The bimodal average of ranges in water levels show that upland areas are more sensitive to recharge than lowland areas. The pattern of yearly mean water levels fluctuates irregularly about a long-term mean value. Abnormally low or high yearly average values that are brought on by periods of drought or excess recharge are short lived; over time, hydrologic conditions shift back to average levels under natural conditions. Wetland areas in the New Jersey Coastal Plain are characterized by ground-water seepage into wide, shallow depressions. Periods of inundation are longest in the deepest part of the depression, whereas inundation of areas near the fringes of wetlands due to ground-water seepage is only seasonal. The seepage face in the fringe areas expand and contract in response to seasonal variation in water-table elevation and in response to precipitation. Values of the aquifer storage coefficient and transmissivity can, in some cases, be determined by use of hydraulic head or streamflow recession analysis as an alternative to aquifer testing. The recession curves developed from hydro graphs of Middle Branch and McDonalds Branch in the New Jersey Coastal Plain indicate that the aquifer near McDonalds Branch has about 2.6 times the storage capacity of the aquifer adjacent to Middle Branch; this finding is consistent with the relatively small ranges of water-level changes measured in McDonalds Branch compared to those measured in Middle Branch.

New Jersey↗

USGS1988

Volatilization of benzene and eight alkyl-substituted benzene compounds from water

Predicting the fate of organic compounds in streams and rivers often requires knowledge of the volatilization characteristics of the compounds. The reference-substance concept, involving laboratory-determined ratios of the liquid-film coefficients for volatilization of the organic compounds to the liquid-film coefficient for oxygen absorption, is used to predict liquid-film coefficients for streams and rivers. In the absence of experimental data, two procedures have been used for estimating these liquid-film coefficient ratios. These procedures, based on the molecular-diffusion coefficient and on the molecular weight, have been widely used but never extensively evaluated. Liquid-film coefficients for the volatilization of benzene and eight alkyl-substituted benzene compounds (toluene through n-octylbenzene) from water were measured in a constant-temperature, stirred water bath. Liquid-film coefficients for oxygen absorption were measured simultaneously. A range of water mixing conditions was used with a water temperature of 298.2 K. The ratios of the liquid-film coefficients for volatilization to the liquid-film coefficient for oxygen absorption for all of the organic compounds were independent of mixing conditions in the water. Experimental ratios ranged from 0.606 for benzene to 0.357 for n-octylbenzene. The molecular-diffusion-coefficient procedure accurately predicted the ratios for ethylbenzene through n-pentylbenzene with a power dependence of 0.566 on the molecular-diffusion coefficient, in agreement with published values. Predicted ratios for benzene and toluene were slightly larger than the experimental ratios. These differences were attributed to possible interactions between the molecules of these compounds and the water molecules and to benzene-benzene interactions that form dimers. Because these interactions also are likely to occur in natural waters, it was concluded that the experimental ratios are more correct than the predicted ratios for application purposes in the reference-substance concept. Predicted ratios for n-hexylbenzene, n-heptylbenzene, and n-octylbenzene were larger than the experimental ratios. These differences were attributed to a sorption-desorption process between these compounds and the surfaces of the constant-temperature water bath. Other experimental problems associated with preparing water solutions of these slightly soluble compounds also may have contributed to the differences. Because these processes are not part of the true volatilization process, it was concluded that the predicted ratios for these three compounds are probably more correct than the experimental ratios for application purposes in the reference-substance concept. Any model of the fate of these compounds in streams and rivers would have to include terms accounting for sorption processes, however. The molecular-weight procedure accurately predicted the ratios for ethylbenzene through n-pentylbenzene, but only if the power dependence on the molecular weight was decreased from the commonly used -0.500 to -0.427. Deviations for the low- and high-molecular-weight compounds were similar to those observed for the molecular-diffusion-coefficient procedure.

Water Supply Paper↗

USGS1997

Tests of subsurface storage of freshwater at Hialeah, Dade County, Florida, and numerical simulation of the salinity of recovered water

Injection and observation wells were drilled in late 1974 for the purpose of conducting tests of storage and recovery of potable water in the brackish Upper Floridan aquifer. Three tests, involving storage and recovery cycles of varying volumes and storage period lengths, were performed between July 1975 and January 1980. Recovery was by natural artesian flow, and recovery efficiencies were 32.9, 47.8, and 38.5 percent. Wellbore plugging occurred during the injection stages, but injectivity was restored by periodic 2- to 3-hour backflushes at the natural artesian flow rate. An interval of shelly limestone between 1,015 and 1,050 feet below land surface contained the flow zone. Data from an analysis of 18 spinner flowmeter logs indicated that the principal part of the flow zone extended from 1,024 to 1,036 feet below land surface and that minor amounts of flow occurred to a depth of about 1,047 feet. A neutron porosity log indicated the bulk porosity of both the flow zone and confining layers to be 35 percent. Chloride and dissolved-solids concentrations of water in the flow zone were 1,200 and 2,700 milligrams per liter, respectively. A three-dimensional, finite-difference flow and solute-transport code was used to simulate pressure data measured during an aquifer test and observed salinity increases in recovered water during storage and recovery cycles. The aquifer test conducted in February 1975 was simulated by using a hydraulic conductivity estimate of 800 feet per day and a rock compressibility estimate of 0.0000400 (pound per square inch)-1. The equivalent transmissivity and storage coefficients were 9,600 cubic feet per day per square foot times foot of aquifer thickness and 7.8×10-5, respectively. Simulation of observed salinity increases during the three recoveries required dispersivities of 65 feet, a molecular diffusivity of 0.0002 foot squared per day, and a regional pore velocity of 260 feet per year. Central differencing in space and time was used for the solute-transport computations as well as an experimental method of computing vertical dispersion that used a scaling factor of 0.013. Additional simulations of the aquifer-test data and recovery salinities were obtained based on assumptions that (1) the flow zone was 21 feet thick, (2) flow-zone effective porosity was 20 percent, and (3) flow-zone hydraulic conductivity was bipolar anisotropic by a ratio of 10:1. The four sets of simulation values were used in model runs in which 10 years of annual injection, storage, and recovery cycles were simulated. Computed recovery efficiencies increased from 40 percent in the first year to 68 percent in later cycles. The high regional pore velocity required for model calibration substantially limited the recovery efficiency achieved in later cycles.

Florida↗

USGS2010

Groundwater-flow model and effects of projected groundwater use in the Ozark Plateaus Aquifer System in the vicinity of Greene County, Missouri — 1907-2030

Recent and historical periods of rapid growth have increased the stress on the groundwater resources in the Ozark aquifer in the Greene County, Missouri area. Historical pumpage from the Ozark aquifer has caused a cone of depression beneath Springfield, Missouri. In an effort to ease its dependence on groundwater for supply, the city of Springfield built a pipeline in 1996 to bring water from Stockton Lake to the city. Rapid population growth in the area coupled with the expanding cone of depression raised concern about the sustainability of groundwater as a resource for future use. A groundwater-flow model was developed by the U.S. Geological Survey in cooperation with Greene County, Missouri, the U. S. Army Corps of Engineers, and the Missouri Department of Natural Resources to assess the effect that increased groundwater demand is having on the long-term availability of groundwater in and around Greene County, Missouri. Three hydrogeologic units were represented in the groundwater-flow model: the Springfield Plateau aquifer, the Ozark confining unit, and the Ozark aquifer. The Springfield Plateau aquifer is less than 350 feet thick in the model area and generally is a low yield aquifer suitable only for domestic use. The Ozark aquifer is composed of a more than 900-foot thick sequence of dolomite and sandstone in the model area and is the primary aquifer throughout most of southern Missouri. Wells open to the entire thickness of the Ozark aquifer typically yield 1,000 gallons per minute or more. Between the two aquifers is the Ozark confining unit composed of as much as 98 feet of shale and limestone. Karst features such as sinkholes, springs, caves, and losing streams are present in both aquifers, but the majority of these features occur in the Springfield Plateau aquifer. The solution-enlarged fracture and bedding plane conduits in the karst system, particularly in the Springfield Plateau aquifer, are capable of moving large quantities of groundwater through the aquifer in relatively short periods of time. Pumpage rates in the model area increased from 1,093,268 cubic feet per day in 1962 to 2,693,423 cubic feet per day in 1987 to 4,330,177 cubic feet per day in 2006. Annual precipitation ranged from 25.21 inches in 1953 to 62.45 inches in 1927 from 1915 to 2006 in the model area. Recharge to the model was calculated as 2.53 percent of the annual precipitation and was varied annually. Recharge was distributed over the model area based on land slope and was adjusted in the city limits of Springfield to account for the impervious surface. A groundwater model with annual stress periods from 1907 to 2030 was developed using a transient calibration period from 1987 to 2006 and a prediction period from 2007 to 2030 to simulate flow in the Springfield Plateau aquifer and the Ozark aquifer. For the model area of approximately 2,870 square miles, the model hydrogeologic units and hydraulic properties were discretized into 253 rows, 316 columns, and 3 layers with the layer boundaries crossing hydrogeologic unit boundaries in some areas. The horizontal cell spacing was 1,000 feet by 1,000 feet. The model was calibrated by minimizing the difference between simulated head and observed water levels and simulated and observed flows in rivers and springs. Population and the associated groundwater use were estimated for 12 communities and the unincorporated area of Greene County based on past growth. Each was analyzed individually, and a low and high annual rate of growth relative to the 2006 population was computed for each community or group. Low growth rates ranged from 0.215 percent per year in Springfield to 6.997 percent per year in Rogersville. Total growth from 2006 to 2030 at the low growth rate ranged from 5.2 percent in Springfield to 167.9 percent in Rogersville. High growth rates ranged from 0.236 percent per year in Springfield to 7.345 percent per year in Rogersville. Total growth from 2006 to 2030 at the high growth rate ranged from 5.7 percent in Springfield to 176.3 percent in Rogersville. Response of the flow system to selected hypothetical pumping stresses and recharge conditions was simulated using the calibrated model. Seven hypothetical scenarios were simulated from 2007 to 2030 to test the effects of various stresses on the head in the Ozark aquifer. Hypothetical scenario 1 continued the 2006 pumping rates without change to the end of 2030. Scenario 2 assumed a low population growth rate with a 4-year drought at the beginning of the prediction period. Scenario 3 assumed a low population growth rate with a 4-year drought at the end of the prediction period. Scenario 4 assumed a high population growth rate with a 4-year drought at the beginning of the prediction period. Scenario 5 assumed a high population growth rate with a 4-year drought at the end of the prediction period. Scenario 6 and 7 had one new industrial well installed within the city limits of Springfield and one new industrial well installed about 3.5 miles east of Rogersville. Scenario 6 assumed a low population growth rate and scenario 7 assumed a high population growth rate. Results were compared by examining differences in head at the end of the simulation period. All scenarios examined resulted in potentiometric-surface declines from 2006 levels. Results from scenario 1 indicated that even with no increase in pumping, the potentiometric surface in the Springfield area continued to decline. The maximum decline of approximately 62 feet from the 2006 potentiometric surface occurred in Springfield. The maximum decline from the 2006 potentiometric surface in scenarios 2 and 3 was approximately 203 feet and in scenarios 4 and 5 was approximately 207 feet. The drought occurring at the end of the simulation period tended to broaden the drawdown area relative to the drought at the beginning. Drought timing did not substantially affect the potentiometric surface in the Ozark aquifer except for where the Ozark aquifer was exposed. Although not a substantial difference, the high population growth rate scenarios tended to have larger declines than the low population growth rate scenarios. As in the previous scenarios, little difference was noted between the low and high growth rate in scenario 6 and 7. Scenarios 6 and 7 showed declines of more than 640 feet from the 2006 potentiometric surface at the new well located in Springfield. The drawdown at the new wells decreased relatively quickly with increased distance from the well. Simulated head in the nearby cities of Nixa, Ozark, and Republic was nearly the same for scenarios 2 through 7 and was lower than the head predicted for scenario 1. Results from scenarios 2 through 7 indicate that the potentiometric surface in 2030 near these cities could decline 100 feet or more from the 2006 levels. Because model layers 2 and 3, representing the Ozark confining unit and most of the thickness of the Ozark aquifer, were simulated as confined, drawdown in the wells in the area of the Ozark aquifer that is unconfined or becomes unconfined during the simulation period will likely be under predicted.

Missouri↗

USGS2012

Evaluation of effects of changes in canal management and precipitation patterns on salinity in Biscayne Bay, Florida, using an integrated surface-water/groundwater model

Biscayne National Park, located in Biscayne Bay in southeast Florida, is one of the largest marine parks in the country and sustains a large natural marine fishery where numerous threatened and endangered species reproduce. In recent years, the bay has experienced hypersaline conditions (salinity greater than 35 practical salinity units) of increasing magnitude and duration. Hypersalinity events were particularly pronounced during April to August 2004 in nearshore areas along the southern and middle parts of the bay. Prolonged hypersaline conditions can cause degradation of water quality and permanent damage to, or loss of, brackish nursery habitats for multiple species of fish and crustaceans as well as damage to certain types of seagrasses that are not tolerant of extreme changes in salinity. To evaluate the factors that contribute to hypersalinity events and to test the effects of possible changes in precipitation patterns and canal flows into Biscayne Bay on salinity in the bay, the U.S. Geological Survey constructed a coupled surface-water/groundwater numerical flow model. The model is designed to account for freshwater flows into Biscayne Bay through the canal system, leakage of salty bay water into the underlying Biscayne aquifer, discharge of fresh and salty groundwater from the Biscayne aquifer into the bay, direct effects of precipitation on bay salinity, indirect effects of precipitation on recharge to the Biscayne aquifer, direct effects of evapotranspiration (ET) on bay salinity, indirect effects of ET on recharge to the Biscayne aquifer, and maintenance of mass balance of both water and solute. The model was constructed using the Flow and Transport in a Linked Overland/Aquifer Density Dependent System (FTLOADDS) simulator, version 3.3, which couples the two-dimensional, surface-water flow and solute-transport simulator SWIFT2D with the density-dependent, groundwater flow an solute-transport simulator SEAWAT. The model was calibrated by a trial-and-error method to fit observed groundwater heads, estimated base flow, and measured bay salinity and temperatures from 1996 to 2004, as well as the location of the freshwater-saltwater interface in the aquifer, by adjusting ET rate limiters, canal vertical hydraulic conductance, leakage rate coefficients (transition-layer thickness and hydraulic conductivity), Manning's n value, and delineation of rainfall zones. Although flow budget calculations indicate that precipitation, ET, and groundwater flux into the bay represent a small portion of the overall budget, these factors may be important in controlling salinity in some parts of the bay, for example the southern parts of the bay where the canal system is not extensively developed or controlled. The balance of precipitation and ET during the wet season generally results in a reduction of bay salinity, whereas the balance of precipitation and ET during the dry season generally results in an increase in bay salinity. During years when wet season precipitation is lower than average, for example less than 70 percent total precipitation for an average year, ET could outweigh precipitation over the bay for essentially the entire year. Hypersaline conditions are prone to occur near the end of the dry season because precipitation rates are generally lower, canal discharge rates (which are strongly correlated to precipitation rates) are also generally lower, and ET rates are higher than during the rest of the year. The hypersalinity event of 2004 followed several years of relatively low precipitation and correspondingly reduced canal structure releases and was unusually extensive, continuing into July. Thus, hypersalinity is ultimately the result of a cumulative deficit of precipitation. The model was used to test the effects of possible changes in canal flux and precipitation. Simulation results showed that by increasing, reducing, or modifying canal discharge rates, the effects on salinity in the bay were more pronounced in the northern part of the bay where there are more canals and canal-control structures. By doubling and halving precipitation, the effects on bay salinity were more pronounced in the southern part of the bay than in the northern part of the bay where there are fewer canals and canal-control structures. The model is designed to quantify factors that contribute to hypersaline conditions in Biscayne Bay and may be less appropriate for addressing other issues or examining conditions substantially different from those described in this report. Model results must be interpreted in light of model limitations, which include representation of the system and conceptual model, uncertainty in physical properties used to describe the system or processes, the scale and discretization of the system, and representation of the boundary conditions.

Florida↗

USGS2008

Sampling design for groundwater solute transport: Tests of methods and analysis of Cape Cod tracer test data

Tests of a one-dimensional sampling design methodology on measurements of bromide concentration collected during the natural gradient tracer test conducted by the U.S. Geological Survey on Cape Cod, Massachusetts, demonstrate its efficacy for field studies of solute transport in groundwater and the utility of one-dimensional analysis. The methodology was applied to design of sparse two-dimensional networks of fully screened wells typical of those often used in engineering practice. In one-dimensional analysis, designs consist of the downstream distances to rows of wells oriented perpendicular to the groundwater flow direction and the timing of sampling to be carried out on each row. The power of a sampling design is measured by its effectiveness in simultaneously meeting objectives of model discrimination, parameter estimation, and cost minimization. One-dimensional models of solute transport, differing in processes affecting the solute and assumptions about the structure of the flow field, were considered for description of tracer cloud migration. When fitting each model using nonlinear regression, additive and multiplicative error forms were allowed for the residuals which consist of both random and model errors. The one-dimensional single-layer model of a nonreactive solute with multiplicative error was judged to be the best of those tested. Results show the efficacy of the methodology in designing sparse but powerful sampling networks. Designs that sample five rows of wells at five or fewer times in any given row performed as well for model discrimination as the full set of samples taken up to eight times in a given row from as many as 89 rows. Also, designs for parameter estimation judged to be good by the methodology were as effective in reducing the variance of parameter estimates as arbitrary designs with many more samples. Results further showed that estimates of velocity and longitudinal dispersivity in one-dimensional models based on data from only five rows of fully screened wells each sampled five or fewer times were practically equivalent to values determined from moments analysis of the complete three-dimensional set of 29,285 samples taken during 16 sampling times.

Water Resources Research↗

USGS1976

Summary appraisals of the nation's ground-water resources – California region

Most people in the California Region live in a semiarid or arid climate, with precipitation less than the potential evapotranspiration- environments of perennial water deficiency. The deficiency becomes most onerous during the characteristically rainless summers and during recurrent droughts that may continue for 10--20 years. However, water from winter rain and snow can be stored for use during the dry summer months, and water stored during a wet climatic period can be used in a succeeding dry period; moreover, perennial deficiency can be overcome by bringing water from areas of perennial surplus. Ground-water reservoirs have especial significance in arid and semiarid regions as repositories where water is stored or can be stored with minimum loss by evaporation. Nearly all the ground-water reservoirs of the California Region are in alluvial sediments of valleys and plains that flank the mountain ranges. The largest, underlying the vast Central Valley, occupies 10 percent of the area of the region, has an estimated usable capacity exceeding 100 million acre-feet (125 cubic kilometres), and has an annual pumpage from wells of about 13 million acre-feet (16 cubic kilometres). Another 10 percent of the region is occupied by 55 developed ground-water reservoirs that are widely distributed; aggregate annual pumpage from them is about 3 1/2 million acre-feet (4 cubic kilometres). In the southeastern desert about 60 ground-water reservoirs occupy still another 10 percent of the region; these have been explored only enough to show that most have some usable water, but current use is negligible. In northeastern California and adjacent Oregon and Nevada, ground-water reservoirs are identified only in valleys and lowlands where wells are feasible, but basaltic rocks of the Cascade Range and Modoc Plateau are excellent aquifers distributed over an area constituting about 15 percent of the region. In sum, slightly less than half the California Region is underlain by ground-water reservoirs, either in valley fill or in volcanic rocks, which can yield significant quantities of water to wells. The rest of the California Region includes the mountains, canyons, slopes, and foothills of the Sierra Nevada, Coast Ranges, and Basin Ranges, whose consolidated rocks and products of their weathering may be permeable locally but are not generally so. Here, the prevailing method of ground-water development is still mostly trial and error, and while in many places a well can yield enough water for a family, some families might have to do without amenities such as flush toilets and automatic washers. For more than half a century the California Region has led all others in North America in pumping of ground water as well as in the area, variety, yield, and export of crops irrigated by water from wells. It has led in the development and use of deep-well turbine pumps for large yield and in the drilling of water wells to great depths. At the same time, such developments have resulted in the elimination of artesian pressures that produced thousands of flowing wells in the 19th century and led to the wide distribution of "falling water tables." Also, California was first to induce encroachment of seawater into wells (in 1906); first to recognize subsidence of land caused by pumping from wells (in 1933), generating news about land sinking in San Jose, Long Beach, and along the Delta-Mendota and Friant-Kern Canals; and first to experience pollution of ground-water reservoirs by brines, chemicals, industrial wastes, and petroleum byproducts including gasoline. The region has led in research in several fields leading to solution of many of these problems. Ground-water problems developed rapidly after World War II with booming population, agriculture, industry, and water demand during several years of regionwide drought. Water levels in wells trended downward almost everywhere as a natural effect of the drought and at accelerated rates in areas of pumping for new enterprises or to supplement subnormal surface-water supplies. The declines in many pumping areas exceeded 100 feet (30 metres), and in some confined aquifers the potentiometric surface was drawn down more than 330 feet (100 metres). The depletion of ground-water storage has had "permanent" side effects, including subsidence of the land exceeding 10 feet (3 metres) in extensive areas, and seawater intrusion that ended the useful lives of many wells along the coast and as much as 6 miles (10 kilometres) inland. Some problems have been solved, but these solutions have at times created other problems. Many ground-water reservoirs have gone through one or more stages - exploration for productive aquifers, exploitation and development for use of the water, restriction to the perennial supply or "safe" yield, importation of surface water, artificial recharge of ground water, conjunctive use of surface and ground water, protection of water quality, and integrated management of use and disposal of water. This evolutionary sequence is unique for each reservoir, and so generalizations become difficult in a regional appraisal; also, the changes with time are significant and varied, and knowledge of prior events is a prerequisite in an appraisal of the resource in a specific year. As of 1970, water levels in many wells had risen significantly from the minimum levels of record reached during the 1960's or earlier; only in areas of new development and in desert areas of long-continued "mining" of nonreplenished water was ground-water storage still being depleted. Land subsidence has continued at diminishing rates and practically has come to a halt in some areas; invading seawater has been stopped or nudged back in most places where problems were significant. The current, favorable situation has been helped by climatic variations, from drought in 1945-52 and exceedingly dry years in 1959 and 1961 to above-normal precipitation in 1969 and 1970; but most of the serious problems have been solved by human efforts, including especially the implementation of the California Water Plan, transporting water from areas of perennial surplus to areas where it is used in lieu of ground water or for ground-water replenishment. All major urban areas now import water to supplement or replace the water pumped from wells. Extensive agricultural areas that formerly were irrigated solely by ground water now obtain some of their water from surface reservoirs and canals, especially in the Central Valley. With surface water available as an alternative supply, well owners can view their ground water with complacency. But complacency can lead to neglect and carelessness and consequent deterioration of the ground-water resource by pollution. Claiming heritage from the English Common Law, the existing California law grants to the landowner (riparian) and private enterprise (appropriator) rights to the water stored in ground-water reservoirs or discharged from them, including the base flow of streams. Ground-water development has been by private and local enterprise, and the California legislature has protected and encouraged local responsibility, control, and management of ground water. As to surface water, a constitutional amendment in 1928 limited riparian rights to the quantities of water that were "reasonably required for the beneficial use to be served." The surpluses have become public waters which are collected, stored, transported, and delivered under various contracts by Federal, State, and other agencies. The agencies have not stored water underground because of uncertainty as to their rights, but some local agencies have been encouraged with favorable pricing schedules to undertake the artificial recharge and management of ground-water reservoirs. Thus, conjunctive use of surface and ground water has become a matter of interagency negotiation. Of all the constraints on effective use of ground-water reservoirs, the most formidable may be the attitudes of people. Assurance of water supply is vital in areas of water deficiency, and Government has assumed increasing responsibility for the welfare of people in these areas. Unfortunately, when Government provides this assurance, most beneficiaries demand continued subsidy to the exclusion of perhaps cheaper private development. Indeed, as the water resources are presently segregated-with private rights predominant in ground water and public interest dominant in surface water-ground-water development has suffered for lack of public concern. The region has the scientific and technologic capability for effective use of groundwater reservoirs, as shown by the achievements and programs of several districts, but many districts are not organized or staffed for such comprehensive management and will need assistance and scientific expertise available from State and Federal agencies. Those agencies, in turn, may not have the scientific data that are essential to prevent haphazard activities and to enable programs to be organized for the most effective and attractive utilization of the water resources. In these days of increasing concern over pollution, existing data are generally inadequate to assess the natural deterioration of ground waters as a basis for defining pollution.

California↗

USGS2020

Groundwater quality in relation to drinking water health standards and geochemical characteristics for 54 domestic wells in Clinton County, Pennsylvania, 2017

Despite the reliance on groundwater by approximately 2.4 million rural Pennsylvania residents, publicly available data to characterize the quality of private well water are limited. As part of a regional effort to characterize groundwater in rural areas of Pennsylvania, samples from 54 domestic wells in Clinton County were collected and analyzed in 2017. The samples were evaluated for a wide range of constituents and compared to drinking-water health standards and geochemical characteristics. The sampled wells were completed to depths ranging from 46 to 500 feet in bedrock that was of predominantly sandstone, shale, or carbonate lithology. Results of this study show that the sampled groundwater quality in Clinton County generally met most drinking-water standards that apply to public water supplies. However, a percentage of samples exceeded drinking-water maximum contaminant levels (MCLs) for total coliform bacteria (57.4 percent), Escherichia coli ( E. coli ) (25.9 percent), nitrate (1.9 percent), and arsenic (1.9 percent); and secondary maximum contaminant levels (SMCLs) for pH (31.5 percent), manganese (29.6 percent), iron (13 percent), total dissolved solids (7.4 percent), aluminum (1.9 percent), and chloride (1.9 percent). Sodium concentrations exceeded the U.S. Environmental Protection Agency drinking-water advisory recommendation in 16.7 percent of the samples. Radon-222 activities exceeded the proposed drinking-water standard of 300 picocuries per liter (pCi/L) in 59.3 percent of the samples. The only volatile organic compounds (VOCs) detected were acetone and methyl ethyl ketone in two separate samples; neither constituent exceeded drinking-water standards. Higher median nitrate concentrations were found in the carbonate (3.26 milligrams per liter [mg/L]) versus shale (less than 0.04 mg/L) and sandstone (0.27 mg/L) aquifer subsets. Most of the elevated nitrate concentrations were associated with E. coli detections in the carbonate aquifers, where transmissive bedrock can facilitate groundwater contamination by human activities at the land surface. The median pH of groundwater from the sandstone aquifers (6.53) was less than those for the shale aquifers (7.31) and carbonate aquifers (7.43). Generally, the lower pH samples had greater potential for elevated concentrations of dissolved metals, including beryllium, copper, lead, nickel, and zinc, whereas the higher pH samples had greater potential for elevated concentrations of total dissolved solids, sodium, fluoride, boron, and uranium. Near-neutral samples (pH 6.5 to 7.5) had greater hardness and alkalinity concentrations than other samples with pH outside this range. Many samples from the shale or sandstone aquifers, particularly those with pH less than 6.5, were identified as having serious potential corrosivity based on the combination of the calcite saturation index and the chloride to sulfate mass ratio; however, none of the samples from the carbonate aquifers was identified as seriously corrosive. Groundwater from 3.7 percent of the wells had concentrations of methane greater than the Pennsylvania action level of 7 mg/L, and 48 of the 54 wells (88.9 percent) had detectable concentrations of methane greater than the 0.0002 mg/L detection limit. Greater methane concentrations were found more frequently in groundwater sampled from the shale aquifers than the carbonate or sandstone aquifers in the study area. Most of the samples containing elevated methane (greater than 0.2 mg/L) were located outside the area of the Appalachian Plateaus. The elevated concentrations of methane generally were associated with suboxic groundwater (dissolved oxygen less than 0.5 mg/L) that had near-neutral to alkaline pH and were correlated with concentrations of iron, manganese, ammonia, sodium, lithium, barium, fluoride, and boron. The stable carbon and hydrogen isotopic compositions of methane in two of four samples analyzed for isotopes were consistent with compositions reported for mud-gas logging samples from gas-bearing geologic units (thermogenic gas) in the Appalachian Plateaus region, whereas two others were consistent with methane of microbial origin or a mixture of microbial and thermogenic gas. Forty-two percent of samples had chloride concentrations greater than 20 mg/L with variable bromide concentrations. Corresponding chloride/bromide ratios are consistent with low-bromide sources such as road-deicing salt and septic effluent or animal waste, or, in a few cases, high-bromide brine. Brines characterized by relatively high bromide are naturally present in deeper parts of the regional groundwater system and, in some cases, may be mobilized by gas drilling. The chloride, bromide, and other constituents in road-deicing salt or brine solutions tend to be diluted by mixing with fresh groundwater in shallow aquifers used for water supply. One of the four groundwater samples with methane concentrations greater than 4 mg/L had chloride and bromide concentrations and a chloride/bromide ratio that indicates mixing with a salinity source such as road-deicing salt, whereas the chloride and bromide concentrations and ratios for the other three high-methane samples indicate mixing with a small amount of brine (0.03 percent or less). In two other eastern Pennsylvania county studies where gas drilling is absent, groundwater with comparable chloride/bromide ratios, bromide, and chloride concentrations plus other element associations have been reported. Additional sampling and analysis, such as isotopic analysis of the dissolved gas, fracture analysis, and more detailed evaluation of surrounding land uses, may be warranted to better understand the origin of the methane and brine constituents in groundwater at specific locations.

Pennsylvania↗

USGS2013

LANDFIRE 2010 - updated data to support wildfire and ecological management

Wildfire is a global phenomenon that affects human populations and ecosystems. Wildfire effects occur at local to global scales impacting many people in different ways (Figure 1). Ecological concerns due to land use, fragmentation, and climate change impact natural resource use, allocation, and conservation. Access to consistent and current environmental data is a constant challenge, yet necessary for understanding the complexities of wildfire and ecological management. Data products and tools from the LANDFIRE Program help decision-makers to clarify problems and identify possible solutions when managing fires and natural resources. LANDFIRE supports the reduction of risk from wildfire to human lives and property, monitoring of fire danger, prediction of fire behavior on active incidents, and assessment of fire severity and impacts on natural systems [1] [2] [3]. LANDFIRE products are unique in that they are nationally consistent and provide the only complete geospatial dataset describing vegetation and wildland fuel information for the entire U.S. As such, LANDFIRE data are useful for many ecological applications [3]. For example, LANDFIRE data were recently integrated into a decision-support system for resource management and conservation decision-making along the Appalachian Trail. LANDFIRE is a joint effort between the U.S. Department of the Interior Office of Wildland Fire, U.S. Department of Agriculture Forest Service Fire & Aviation Management, and The Nature Conservancy. To date, seven versions of LANDFIRE data have been released, with each successive version improving the quality of the data, adding additional features, and/or updating the time period represented by the data. The latest version, LANDFIRE 2010 (LF 2010), released mid-2013, represents circa 2010 landscape conditions and succeeds LANDFIRE 2008 (LF 2008), which represented circa 2008 landscape conditions. LF 2010 used many of the same processes developed for the LF 2008 effort [3]. Ongoing refinement of the LANDFIRE vegetation and fuel data is necessary to improve the quality and usability of the data and to capture landscape disturbance. LANDFIRE relies on Landsat multi-spectral imagery to produce and update vegetation and fuel data. The deep Landsat archive provides data needed for vegetation classification, change analysis, and historical disturbance characterization, for which LANDFIRE has used more than 24,000 image scenes since the program’s inception. In addition, LF 2010 used airborne and spaceborne lidar, and spaceborne synthetic aperture radar (SAR) to map vegetation structure in areas where ground-based field information was lacking, including Alaska and U.S.-affiliated islands in the Caribbean and the Pacific. The mapping of insular areas is new for the 2010 data release; previous versions of LANDFIRE were limited to the conterminous U.S., Alaska, and Hawaii.

Earthzine↗

USGS2010

Vadose zone attenuation of organic compounds at a crude oil spill site - Interactions between biogeochemical reactions and multicomponent gas transport

Contaminant attenuation processes in the vadose zone of a crude oil spill site near Bemidji, MN have been simulated with a reactive transport model that includes multicomponent gas transport, solute transport, and the most relevant biogeochemical reactions. Dissolution and volatilization of oil components, their aerobic and anaerobic degradation coupled with sequential electron acceptor consumption, ingress of atmospheric O 2 , and the release of CH 4 and CO 2 from the smear zone generated by the floating oil were considered. The focus of the simulations was to assess the dynamics between biodegradation and gas transport processes in the vadose zone, to evaluate the rates and contributions of different electron accepting processes towards vadose zone natural attenuation, and to provide an estimate of the historical mass loss. Concentration distributions of reactive (O 2 , CH 4 , and CO 2 ) and non-reactive (Ar and N 2 ) gases served as key constraints for the model calibration. Simulation results confirm that as of 2007, the main degradation pathway can be attributed to methanogenic degradation of organic compounds in the smear zone and the vadose zone resulting in a contaminant plume dominated by high CH 4 concentrations. In accordance with field observations, zones of volatilization and CH 4 generation are correlated to slightly elevated total gas pressures and low partial pressures of N 2 and Ar, while zones of aerobic CH 4 oxidation are characterized by slightly reduced gas pressures and elevated concentrations of N 2 and Ar. Diffusion is the most significant transport mechanism for gases in the vadose zone; however, the simulations also indicate that, despite very small pressure gradients, advection contributes up to 15% towards the net flux of CH 4 , and to a more limited extent to O 2 ingress. Model calibration strongly suggests that transfer of biogenically generated gases from the smear zone provides a major control on vadose zone gas distributions and vadose zone carbon balance. Overall, the model was successful in capturing the complex interactions between biogeochemical reactions and multicomponent gas transport processes. However, despite employing a process-based modeling approach, honoring observed parameter ranges, and generally obtaining good agreement between field observations and model simulations, accurate quantification of natural attenuation rates remains difficult. The modeling results are affected by uncertainties regarding gas phase saturations, tortuosities, and the magnitude of CH 4 and CO 2 flux from the smear zone. These findings highlight the need to better delineate gas fluxes at the model boundaries, which will help constrain contaminant degradation rates, and ultimately source zone longevity.

Minnesota↗

USGS1999

Estimating Concentrations of Road-Salt Constituents in Highway-Runoff from Measurements of Specific Conductance

Discrete or composite samples of highway runoff may not adequately represent in-storm water-quality fluctuations because continuous records of water stage, specific conductance, pH, and temperature of the runoff indicate that these properties fluctuate substantially during a storm. Continuous records of water-quality properties can be used to maximize the information obtained about the stormwater runoff system being studied and can provide the context needed to interpret analyses of water samples. Concentrations of the road-salt constituents calcium, sodium, and chloride in highway runoff were estimated from theoretical and empirical relations between specific conductance and the concentrations of these ions. These relations were examined using the analysis of 233 highwayrunoff samples collected from August 1988 through March 1995 at four highway-drainage monitoring stations along State Route 25 in southeastern Massachusetts. Theoretically, the specific conductance of a water sample is the sum of the individual conductances attributed to each ionic species in solution-the product of the concentrations of each ion in milliequivalents per liter (meq/L) multiplied by the equivalent ionic conductance at infinite dilution-thereby establishing the principle of superposition. Superposition provides an estimate of actual specific conductance that is within measurement error throughout the conductance range of many natural waters, with errors of less than ?5 percent below 1,000 microsiemens per centimeter (?S/cm) and ?10 percent between 1,000 and 4,000 ?S/cm if all major ionic constituents are accounted for. A semi-empirical method (adjusted superposition) was used to adjust for concentration effects-superposition-method prediction errors at high and low concentrations-and to relate measured specific conductance to that calculated using superposition. The adjusted superposition method, which was developed to interpret the State Route 25 highway-runoff records, accounts for contributions of constituents other than calcium, sodium, and chloride in dilute waters. The adjusted superposition method also accounts for the attenuation of each constituent's contribution to conductance as ionic strength increases. Use of the adjusted superposition method generally reduced predictive error to within measurement error throughout the range of specific conductance (from 37 to 51,500 ?S/cm) in the highway runoff samples. The effects of pH, temperature, and organic constituents on the relation between concentrations of dissolved constituents and measured specific conductance were examined but these properties did not substantially affect interpretation of the Route 25 data set. Predictive abilities of the adjusted superposition method were similar to results obtained by standard regression techniques, but the adjusted superposition method has several advantages. Adjusted superposition can be applied using available published data about the constituents in precipitation, highway runoff, and the deicing chemicals applied to a highway. This semi-empirical method can be used as a predictive and diagnostic tool before a substantial number of samples are collected, but the power of the regression method is based upon a large number of water-quality analyses that may be affected by a bias in the data.

Water-Resources Investigations Report↗

USGS1988

Proceedings of a workshop on the development and evaluation of habitat suitability criteria: A compilation of papers and discussions presented at Colorado State University, Fort Collins, Colorado, December 8-12, 1986

The development of reliable habitat suitability criteria is critical to the successful implementation of the Instream Flow Incremental Methodology (IFIM), or any other habitat based evaluation technology. It is also a fascinating topic of research, for several reasons. First, the “science” of habitat quantification is relatively young. Descriptions of habitat use and partitioning can be traced back to Darwin, if not further. Attempts to actually quantify habitat use can be found predominantly during the last two decades, with most of the activity occurring in about the last five years. Second, this work is challenging because we are usually working with fish or some other organism that lives out of sight in an environment that is foreign to humans. Most of the data collection techniques that have been developed for standard fisheries work are unsuited, without modification, for criteria development. These factors make anyone involved in this type of research a pioneer, of sorts. Pioneers often make new and wonderful discoveries, but they also sometimes get lost. In our opinion, however, there is an even more rewarding aspect to criteria development research. It seems that the field of biology has tended to become increasingly clinical over the years. Criteria development demands the unobtrusive observation of organisms in their natural environment, a fact that allows the biological to be a naturalist and still get paid for it. The relative youth and importance of habitat quantification have resulted in rapid advancements in the state of the art. The expansion of methods is vividly demonstrated simply by comparing the two Instream Flow Information Papers written on the subject in 1978 and in 1986. One of the missions of the Aquatic Systems Branch (formerly the Instream Flow Group) is to serve as a clearinghouse for new techniques and methods. In keeping with this role, a workshop was conducted during December 1986 to discuss current and newly evolving methods for developing and evaluating habitat suitability criteria. Participation in this workshop was largely by invitation only. The objective was to obtain insights into problems and possible solutions to criteria development, from the perspective of professionals closely involved with the subject. These proceedings of that workshop are intended to supplement the information contained in Instream Flow Information Paper 21, "Development and Evaluation of Habitat Suitability Criteria for Use in the Instream Flow Incremental Methodology." The workshop was closely arranged in five sessions, roughly following the outline of Information Paper 21. The first session dealt with various aspects of study design and how they can influence the outcome of a study. Session two investigated techniques for developing criteria from professional judgment, and some of the problems encountered when personal or agency prejudice enters the picture. Session three concentrated on field data collection procedures, whereas session four examined methods of converting field data into curves. Field verification studies were discussed in session five. Each presentation in the workshop was followed by a question and answer period of 15 to 30 minutes. These discussions were recorded, transcribed, and appended to the end of each paper in these proceedings. We have attempted to capture the essence of these discussions as accurately as possible, but hope that the reader can appreciate the difficulty in translating a free-ranging discussion (from a barely audible tape) to something that makes sense in print. These question and answer sessions constitute the peer review for each of the papers. This provides the reader with the unique opportunity to review the interactions between authors and reviewers.

Book↗

USGS1964

Deep geothermal brine near Salton Sea, California

A well drilled for geothermal power near Salton Sea in Imperial Valley, Calif., is 5,232 feet deep; it is the deepest well in the world (1962) in a high-temperature hot spring area. In the lower half of the hole temperatures are too high to measure with available equipment, but are at loast 270°C, and may be as much as 370°C. For comparison, maximum temperature heretofore reported at depth (1962) for hot spring areas is 295°C. The well taps a very saline brine of Na-Ca-K-Cl type (about 185,000 ppm Cl) with exceptionally high potassium, and with the highest content of minor alkali elements known for natural waters; Fe, Mn, Zn, Pb, Cu, Ag, and some other metals are also exceptionally high. This brine may be connate, but present evidence favors a source in the magma chamber at depth that supplied late Quaternary rhyolite domes of the area. If the latter is correct, the brine is an undiluted magmatic water that is residual from the separation of a more volatile phase high in CO 2 , H 2 S, and with some alkali halides. Elsewhere, the hypothesized volatile phase may account for near-surface hot spring activity of most thermal areas of volcanic association. The residual brine of high salinity may ordinarily remain relatively deep in the volcanic systems because of high specific gravity and low content of volatiles, seldom appearing at the surface except in a greatly diluted form. The hot springs of Arima, Japan, may be a rare example of this type of magmatic water discharging at the surface in moderate concentration (Cl as much as 42,000 ppm). Independent evidence from fluid inclusions in minerals of high-temperature base-metal deposits also favors the existence of magmatic water high in Na, Ca, and Cl, and low in CO 2 and other volatile components. During a three-month production test several tons of material precipitated in the horizontal discharge pipe from the well. Amorphous silica with iron and manganese, and bornite are the dominant recognized components. This material contains the astonishingly high contents of about 20 percent copper, 2 percent silver, and notable sulfur, arsenic, bismuth, lead, antimony, and some other minor elements. Total quantities of all elements in the original whole brine are not yet known, but calculated amounts corresponding to 1 to 3 ppm of copper and 0.1 to 0.3 ppm of silver were precipitated from the brine to form the pipe deposits. The brine, therefore, may be man’s first sample of an « active » ore solution. Equally fascinating to many geologists is the possibility that in the lower part of the hole temperatures are so high and pressures are sufficient for young sedimentary rocks to be undergoing transformation into rocks with mineral assemblages of the greenschist facies of metamorphism. Drill cores from 4,400 to 5,000 feet in depth contain chlorite, albite, K-feldspar, epidote, mica, and quartz, with some indication of increase in metamorphic grade downward. Regional geological and geophysical studies favor a depth of about 20,000 feet to pre-Tertiary basement rocks in the general area. A shallow basement or local upfaulting of old metamorphic rocks are not likely possibilities for the thermal area.

California↗

USGS1994

User's guide to revised method-of-characteristics solute-transport model (MOC--version 31)

The U.S. Geological Survey computer model to simulate two-dimensional solute transport and dispersion in ground water (Konikow and Bredehoeft, 1978; Goode and Konikow, 1989) has been modified to improve management of input and output data and to provide progressive run-time information. All opening and closing of files are now done automatically by the program. Names of input data files are entered either interactively or using a batch-mode script file. Names of output files, created automatically by the program, are based on the name of the input file. In the interactive mode, messages are written to the screen during execution to allow the user to monitor the status and progress of the simulation and to anticipate total running time. Information reported and updated during a simulation include the current pumping period and time step, number of particle moves, and percentage completion of the current time step. The batch mode enables a user to run a series of simulations consecutively, without additional control. A report of the model's activity in the batch mode is written to a separate output file, allowing later review. The user has several options for creating separate output files for different types of data. The formats are compatible with many commercially available applications, which facilitates graphical postprocessing of model results. Geohydrology and Evaluation of Stream-Aquifer Relations in the Apalachicola-Chattahoochee-Flint River Basin, Southeastern Alabama, Northwestern Florida, and Southwestern Georgia By Lynn J. Torak, Gary S. Davis, George A. Strain, and Jennifer G. Herndon Abstract The lower Apalachieola-Chattahoochec-Flint River Basin is underlain by Coastal Plain sediments of pre-Cretaceous to Quaternary age consisting of alternating units of sand, clay, sandstone, dolomite, and limestone that gradually thicken and dip gently to the southeast. The stream-aquifer system consism of carbonate (limestone and dolomite) and elastic sediments, which define the Upper Floridan aquifer and Intermediate system, in hydraulic connection with the principal rivers of the basin and other surface-water features, natural and man made. Separate digital models of the Upper Flori-dan aquifer and Intermediate system were constructed by using the U.S. Geological Survey's MODular Finite-Element model of two dimensional ground-water flow, based on concep- tualizations of the stream-aquifer system, and calibrated to drought conditions of October 1986. Sensitivity analyses performed on the models indicated that aquifer hydraulic conductivity, lateral and vertical boundary flows, and pumpage have a strong influence on groundwater levels. Simulated pumpage increases in the Upper Floridan aquifer, primarily in the Dougherty Plain physiographic district of Georgia,. caused significant reductions in aquifer discharge to streams that eventually flow to Lake Seminole and the Apalachicola River and Bay. Simulated pumpage increases greater than 3 times the October 1986 rates caused drying ofsome stream reaches and parts of the Upper Floridan aquifer in Georgia. Water budgets prepared from simulation results indicate that ground- water discharge to streams and recharge by horizontal and vertical flow are the principal mechanisms for moving water through the flow system. The potential for changes in ground-water quality is high in areas where chemical constituents can be mobilized by these mechanisms. Less than 2 percent of ground-water discharge to streams comes from the Intermediate system; thus, it plays a minor role in the hydrodynamics of the stream- aquifer system.

Water-Resources Investigations Report↗

USGS2022

Coupling validation effort with in situ bioacoustic data improves estimating relative activity and occupancy for multiple species with cross-species misclassifications

The increasing complexity and pace of ecological change requires natural resource managers to consider entire species assemblages. Acoustic recording units (ARUs) require minimal cost and effort to deploy and inform relative activity, or encounter rates, for multiple species simultaneously. ARU-based surveys require post-processing of the recordings via software algorithms that assign a species label to each recording. The automated classification process can result in cross-species misidentifications that should be accounted for when employing statistical modelling for conservation decision-making. Using simulation and ARU-based detection counts from 17 bat species in British Columbia, Canada, we investigate three strategies for adjusting statistical inference for species misclassification: (a) ‘coupling’ ambiguous and unambiguous detections by validating a subset of survey events post-hoc, (b) using a calibration dataset on the software algorithm's (in)accuracy for species identification or (c) specifying informative Bayesian priors on classification probabilities. We explore the impact of different Bayesian prior specifications for the classification probabilities on posterior estimation. We then consider how the quantity of data validated post-hoc impacts model convergence and resulting inferences for bat species relative activity as related to nightly conditions and yearly site occupancy after accounting for site-level environmental variables. Coupled methods resulted in less bias and uncertainty when estimating relative activity and species classification probabilities relative to calibration approaches. We found that species that were difficult-to-detect and those that were often inaccurately identified by the software required more validation effort than more easily detected and/or identified species. Our results suggest that, when possible, acoustic surveys should rely on coupled validated detection information to account for false-positive detections, rather than uncoupled calibration datasets. However, if the assemblage of interest contains a large number of rarely detected or less prevalent species, an intractable amount of effort may be required, suggesting there are benefits to curating a calibration dataset that is representative of the observation process. Our findings provide insights into the practical challenges associated with statistical analyses of ARU data and possible analytical solutions to support reliable and cost-effective decision-making for wildlife conservation/management in the face of known sources of observation errors.

British Columbia↗