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At least 1,135 records · Page 63Linked to original sources
USGS1999

Loch Vale Watershed Project quality assurance report, 1995-1998

The Loch Vale Watershed (LVWS) project was initiated in 1980 by the National Park Service with funding from the Aquatic Effects Research Program of the National Acid Precipitation Assessment Program. Initial research objectives were to understand the processes that would either mitigate or accelerate the effects of pollution on soil and surface water chemistry, and to build a record in which long-term trends could be identified and examined. It is important for all data collected in Loch Vale to meet the high standards of quality set forth in previous LVWS QA/QC reports and LVWS Methods Manuals. Given the ever-widening usage of data collected in Loch Vale, it is equally important to provide users of that data with a report assuring that all data are sound. Parameters covered in this report are the quality of meteorological measurements, hydrological measurements, surface water chemistry, and similarities in catch efficiency of two raingage types in Loch Vale for the period of 1995-1998. Routine sampling of weather conditions, precipitation chemistry, and stream/lake water chemistry began in 1982. Since then, all samples and data have been analyzed according to widely accepted and published methods. Weather data have been collected, analyzed, and stored by LVWS project personnel. Methods for the handling of meteorological data are well documented (Denning 1988, Edwards 1991, Newkirk 1995,and Allstott 1995). Precipitation chemistry has always been collected according to National Atmospheric Deposition Program protocol (Bigelow 1988), and analyzed at the Central Analytical Laboratory of the Illinois State Water Survey in Champaign, IL. QA/QC procedures of the National Atmospheric Deposition Program are well documented (Aubertin 1990). Protocols for sampling surface waters are also well documented (Newkirk 1995). Analysis of surface water chemistry has been performed using standard EPA protocol at the US Forest Service's Rocky Mt. Station Biogeochemistry Laboratory since 1993.

Open-File Report↗
USGS2008

Radar interferometry observations of surface displacements during pre- and coeruptive periods at Mount St. Helens, Washington, 1992-2005

We analyzed hundreds of interferograms of Mount St. Helens produced from radar images acquired by the ERS-1/2, ENVISAT, and RADARSAT satellites during the 1992-2004 preeruptive and 2004-2005 coeruptive periods for signs of deformation associated with magmatic activity at depth. Individual interferograms were often contaminated by atmospheric delay anomalies; therefore, we employed stacking to amplify any deformation patterns that might exist while minimizing random noise. Preeruptive interferograms show no signs of volcanowide deformation between 1992 and the onset of eruptive activity in 2004. Several patches of subsidence in the 1980 debris-avalanche deposit were identified, however, and are thought to be caused by viscoelastic relaxation of loosely consolidated substrate, consolidation of water-saturated sediment, or melting of buried ice. Coeruptive interferometric stacks are dominated by atmospheric noise, probably because individual interferograms span only short time intervals in 2004 and 2005. Nevertheless, we are confident that at least one of the seven coeruptive stacks we constructed is reliable at about the 1-cm level. This stack suggests deflation of Mount St. Helens driven by contraction of a source beneath the volcano.

Washington↗
USGS2015

Mercury and methylmercury in reservoirs in Indiana

Mercury (Hg) is an element that occurs naturally, but evidence suggests that human activities have resulted in increased amounts being released to the atmosphere and land surface. When Hg is converted to methylmercury (MeHg) in aquatic ecosystems, MeHg accumulates and increases in the food web so that some fish contain levels which pose a health risk to humans and wildlife that consume these fish. Reservoirs unlike natural lakes, are a part of river systems that are managed for flood control. Data compiled and interpreted for six flood-control reservoirs in Indiana showed a relation between Hg transport, MeHg formation in water, and MeHg in fish that was influenced by physical, chemical, and biological differences among the reservoirs. Existing information precludes a uniform comparison of Hg and MeHg in all reservoirs in the State, but factors and conditions were identified that can indicate where and when Hg and MeHg levels in reservoirs could be highest. As part of a statewide monitoring network for Hg and MeHg in Indiana streams, 66 water samples were collected from four reservoir tailwater sites (downstream near the dams) on a quarterly schedule for 5 years. The reservoirs were Brookville Lake, Cagles Mill Lake, J. Edward Roush Lake, and Mississinewa Lake. Particulate-bound Hg concentrations were significantly lower in tailwater samples than in samples from free-flowing streams in the statewide network. (Free-flowing streams were not affected by dams and were not upstream from these reservoirs.) These data indicated the reduced flow velocity of water upstream from dams was allowing particulate-bound Hg to settle out of the water in the reservoir pools. The concentration ratios of MeHg to Hg were significantly higher in the tailwater samples than in samples from free-flowing streams, and the MeHg to Hg ratios were significantly higher in summer than in other seasons. To evaluate the conditions related to MeHg formation, pools of three reservoirs (Brookville Lake, Monroe Lake, and Patoka Lake) were investigated during summer hydrologic conditions. Water temperature and dissolved oxygen were measured from the water surface to the lake bottom at 10 to 17 transects across each reservoir to identify three thermal strata, defined by water temperature, dissolved oxygen concentration, and depth. Depth-specific water samples were collected from these thermal strata throughout each reservoir, from the headwaters to the dam and from the tailwater. Mercury concentrations higher than 0.04 nanogram per liter (ng/L) were detected in all 53 samples, and MeHg concentrations higher than 0.04 ng/L were detected in 53 percent of the samples. The investigation found a zone of water below 8 or 9 meters, with temperatures less than 18 degrees Celsius and dissolved oxygen less than 3.5 milligrams per liter, extending through nearly half the reservoir area in Monroe Lake and Patoka Lake. This zone had abundant dissolved MeHg and concentration ratios of dissolved MeHg to Hg that ranged from 25 to 82 percent. This zone also had water with pH less than 7 and decreased dissolved sulfate, conditions indicating sulfate reduction by microorganisms that promoted a high potential for the conversion of Hg to MeHg. Reservoir outflow came from this zone at Monroe Lake and contributed to a tailwater concentration ratio for dissolved MeHg to Hg of 56 percent. Reservoir outflow at Patoka Lake was not from this zone, and dissolved MeHg was not detected in the tailwater. In contrast, samples from the summer pool at Brookville Lake had no MeHg detections even though Hg was detected, probably because the water pH higher than 7 inhibited sulfate reduction and did not promote the conversion of Hg to MeHg. Mercury and MeHg concentrations and the concentration ratios of MeHg to Hg in water varied among the six reservoirs in Indiana, and the differences were related to a combination of factors that could apply to other reservoirs. In areas with moderate to high rates of atmospheric Hg wet and dry deposition, Hg runoff and transport to streams and reservoirs was potentially highest for reservoirs with heavily forested watersheds in steep terrains of near-surface bedrock. Methylmercury concentrations and concentration ratios of MeHg to Hg were highest for reservoirs with the longest summer pools and highest inflow-to-outflow retention times, where water-chemistry conditions favoring sulfate reduction promoted conversion of Hg to MeHg. Methylmercury (reported as Hg) in fish-tissue samples collected for the State fish consumption advisory program was used to describe MeHg food-web accumulation and magnification in the reservoirs. The highest percentages of fish-tissue samples with Hg concentrations that exceeded the criterion of 0.30 milligram per kilogram for protection of human health were from Monroe Lake (38 percent) and Patoka Lake (33 percent). A review of the number and size of fish species caught from these two reservoirs resulted in two implications for fish consumption by humans. First, the highest numbers of fish harvested for potential human consumption were species more likely to have MeHg concentrations lower than the human-health criterion (crappie, bluegill, and catfish). Second, although largemouth bass were likely to have MeHg concentrations higher than the human-health criterion, they were caught and released more often than they were harvested. However, the average size largemouth bass (in both reservoirs) and above-average size walleye (in Monroe Lake) that were harvested for potential human consumption were likely to have MeHg concentrations higher than the human-health criterion.

Indiana↗
USGS2023

Environmental tracers of groundwater source, age, and geochemical evolution

Hexavalent chromium, Cr(VI), was discharged in cooling wastewater to unlined surface ponds from 1952 to 1964 and reached the underlying unconsolidated aquifer at the Pacific Gas and Electric Company (PG&E) Hinkley compressor station in the Mojave Desert, 80 miles northeast of Los Angeles, California. A suite of environmental tracers was analyzed in water samples collected from more than 100 wells to characterize the source, age, and geochemical evolution of groundwater within and near the Cr(VI) plume in Hinkley and Water Valleys. This information was used to help determine the extent of Cr(VI) associated with releases from the Hinkley compressor station and to identify Cr(VI) associated with natural sources. The source of water in most wells, indicated by stable oxygen and hydrogen isotope values for water, delta oxygen-18 and delta deuterium, was recharge by infiltration of intermittent surface flows in the Mojave River. With the exception of small flows in 1958, the Mojave River was largely dry between 1952 and 1969. This dry period spans the period of Cr(VI) releases from the Hinkley compressor station; 1952–69 also spans the period of high tritium levels in precipitation resulting from the atmospheric testing of nuclear weapons and, as a consequence, tritium concentrations in groundwater in Hinkley Valley were comparatively low. Groundwater ages (time since recharge) increased downgradient from the Mojave River and with depth. Tritium, measured by helium ingrowth with a study reporting level of 0.05 tritium unit, was detected in water from 51 percent of wells, with detectable tritium as far as 7 miles downgradient from the Mojave River. Tritium concentrations were higher, and tritium/helium-3 groundwater ages younger, in water from wells near the Mojave River and in water from shallower wells downgradient. Agricultural pumping has decreased groundwater levels as much as 60 feet since 1952. As a result of this pumping, some groundwater containing tritium, and presumably anthropogenic Cr(VI), has been removed from the aquifer. The distribution of wells having carbon-14 activities near or greater than 100-percent modern carbon, consistent with post-1952 recharge water, was similar to the distribution of wells containing detectable tritium. Carbon-14 activities as low as 8.9-percent modern carbon, with carbon-14 ages (unadjusted for reactions with aquifer materials) of almost 20,000 years before present (ybp), were sampled in water from some deep wells. Hexavalent chromium concentrations in older groundwater were as high as 11 micrograms per liter but did not exceed 3.6 micrograms per liter in older water from wells completed in “Mojave-type” deposits (composed of felsic Mojave River stream and near-shore lake deposits sourced from the Mojave River); this value may represent an upper limit on Cr(VI) concentrations in groundwater within Mojave-type deposits that likely approximates background Cr(VI) concentrations in the study area. Chlorofluorocarbons were released to the atmosphere and hydrologic cycle as a result of industrial activity beginning in the 1930s. Chlorofluorocarbon data were not generally suitable for groundwater-age dating in Hinkley and Water Valley because of nonatmospheric contributions from local sources. Strontium-87/86 isotope ratios and stable chromium isotopes, delta chromium-53, provide information on the geochemical evolution of groundwater in the aquifer. Highly radiogenic strontium-87/86 ratios greater than 0.71000 were present in water from wells completed in coarse-textured Mojave-type deposits having low chromium concentrations but were not diagnostic of these materials. Nonradiogenic strontium-87/86 ratios less than 0.70950 were diagnostic of weathered materials in the northern subarea of Hinkley and in Water Valley that were eroded from Miocene (23–5 million ybp) deposits east of the study area. Values for delta chromium-53 ranged from near 0 to 2.8 parts per thousand (‰) difference. The extent of reductive fractionation, mixing with native groundwater, and longitudinal dispersion within the October–December 2015 (Q4 2015) regulatory Cr(VI) plume can be estimated on the basis of the delta chromium-53 isotope composition of groundwater within the plume. Reduction of Cr(VI) to trivalent chromium, Cr(III), can occur in the presence of natural reductants in oxic groundwater. Although not diagnostic of anthropogenic chromium at the concentrations of interest near the Q4 2015 regulatory Cr(VI) plume margin, delta chromium-53 data indicate anthropogenic Cr(VI) within the plume is not conservative and has reacted with aquifer materials; these reactions have removed some anthropogenic Cr(VI) from groundwater. Environmental tracers, and the distribution of modern (post-1952) and premodern (pre-1952) groundwater, inform understanding of the extent of anthropogenic and naturally occurring Cr(VI) near the Q4 2015 regulatory Cr(VI) plume and the understanding of geochemical processes occurring in and near the margins of the Cr(VI) plume. The oxygen and hydrogen isotope compositions of water, tritium/helium-3 groundwater-age data, and carbon-14 data were used with mineralogy and chemistry data as part of a summative-scale analysis to determine the Cr(VI) plume extent later in this professional paper (chapter G).

California↗
USGS2014

Geologic map of Mars

This global geologic map of Mars, which records the distribution of geologic units and landforms on the planet's surface through time, is based on unprecedented variety, quality, and quantity of remotely sensed data acquired since the Viking Orbiters. These data have provided morphologic, topographic, spectral, thermophysical, radar sounding, and other observations for integration, analysis, and interpretation in support of geologic mapping. In particular, the precise topographic mapping now available has enabled consistent morphologic portrayal of the surface for global mapping (whereas previously used visual-range image bases were less effective, because they combined morphologic and albedo information and, locally, atmospheric haze). Also, thermal infrared image bases used for this map tended to be less affected by atmospheric haze and thus are reliable for analysis of surface morphology and texture at even higher resolution than the topographic products.

Scientific Investigations Map↗
USGS2004

Estimation of Total Nitrogen and Phosphorus in New England Streams Using Spatially Referenced Regression Models

The U.S. Geological Survey (USGS), in cooperation with the U.S. Environmental Protection Agency (USEPA) and the New England Interstate Water Pollution Control Commission (NEIWPCC), has developed a water-quality model, called SPARROW (Spatially Referenced Regressions on Watershed Attributes), to assist in regional total maximum daily load (TMDL) and nutrient-criteria activities in New England. SPARROW is a spatially detailed, statistical model that uses regression equations to relate total nitrogen and phosphorus (nutrient) stream loads to nutrient sources and watershed characteristics. The statistical relations in these equations are then used to predict nutrient loads in unmonitored streams. The New England SPARROW models are built using a hydrologic network of 42,000 stream reaches and associated watersheds. Watershed boundaries are defined for each stream reach in the network through the use of a digital elevation model and existing digitized watershed divides. Nutrient source data is from permitted wastewater discharge data from USEPA's Permit Compliance System (PCS), various land-use sources, and atmospheric deposition. Physical watershed characteristics include drainage area, land use, streamflow, time-of-travel, stream density, percent wetlands, slope of the land surface, and soil permeability. The New England SPARROW models for total nitrogen and total phosphorus have R-squared values of 0.95 and 0.94, with mean square errors of 0.16 and 0.23, respectively. Variables that were statistically significant in the total nitrogen model include permitted municipal-wastewater discharges, atmospheric deposition, agricultural area, and developed land area. Total nitrogen stream-loss rates were significant only in streams with average annual flows less than or equal to 2.83 cubic meters per second. In streams larger than this, there is nondetectable in-stream loss of annual total nitrogen in New England. Variables that were statistically significant in the total phosphorus model include discharges for municipal wastewater-treatment facilities and pulp and paper facilities, developed land area, agricultural area, and forested area. For total phosphorus, loss rates were significant for reservoirs with surface areas of 10 square kilometers or less, and in streams with flows less than or equal to 2.83 cubic meters per second. Applications of SPARROW for evaluating nutrient loading in New England waters include estimates of the spatial distributions of total nitrogen and phosphorus yields, sources of the nutrients, and the potential for delivery of those yields to receiving waters. This information can be used to (1) predict ranges in nutrient levels in surface waters, (2) identify the environmental variables that are statistically significant predictors of nutrient levels in streams, (3) evaluate monitoring efforts for better determination of nutrient loads, and (4) evaluate management options for reducing nutrient loads to achieve water-quality goals.

Scientific Investigations Report↗
USGS2004

Predicting water quality by relating secchi-disk transparency and chlorophyll a measurements to satellite imagery for Michigan inland lakes, August 2002

Inland lakes are an important economic and environmental resource for Michigan. The U.S. Geological Survey and the Michigan Department of Environmental Quality have been cooperatively monitoring the quality of selected lakes in Michigan through the Lake Water Quality Assessment program. Through this program, approximately 730 of Michigan's 11,000 inland lakes will be monitored once during this 15-year study. Targeted lakes will be sampled during spring turnover and again in late summer to characterize water quality. Because more extensive and more frequent sampling is not economically feasible in the Lake Water Quality Assessment program, the U.S. Geological Survey and Michigan Department of Environmental Quality investigate the use of satellite imagery as a means of estimating water quality in unsampled lakes. Satellite imagery has been successfully used in Minnesota, Wisconsin, and elsewhere to compute the trophic state of inland lakes from predicted secchi-disk measurements. Previous attempts of this kind in Michigan resulted in a poorer fit between observed and predicted data than was found for Minnesota or Wisconsin. This study tested whether estimates could be improved by using atmospherically corrected satellite imagery, whether a more appropriate regression model could be obtained for Michigan, and whether chlorophyll a concentrations could be reliably predicted from satellite imagery in order to compute trophic state of inland lakes. Although the atmospheric-correction did not significantly improve estimates of lake-water quality, a new regression equation was identified that consistently yielded better results than an equation obtained from the literature. A stepwise regression was used to determine an equation that accurately predicts chlorophyll a concentrations in northern Lower Michigan.

Michigan↗
USGS2004

Hydrology and cycling of nitrogen and phosphorus in Little Bean Marsh: A remnant riparian wetland along the Missouri River in Platte County, Missouri, 1996–97

The lack of concurrent water-quality and hydrologic data on riparian wetlands in the Midwestern United States has resulted in a lack of knowledge about the water-quality functions that these wetlands provide. Therefore, Little Bean Marsh, a remnant riparian wetland along the Missouri River, was investigated in 1996 and 1997 primarily to determine the magnitude and character of selected water-quality benefits that can be produced in such a wetland and to identify critical processes that can be managed in remnant or restored riparian wetlands for amelioration of water quality. Little Bean Marsh averages 69 hectares in size, has a maximum depth of about 1 meter, and the majority of the marsh is covered by macrophytes. In 1997, 41 percent of the water received by Little Bean Marsh was from direct precipitation, 14 percent was from ground-water seepage, 30 percent from watershed runoff, and 15 percent was backflow from Bean Lake. Although, Little Bean Marsh was both a ground-water recharge and discharge area, discharge to the marsh was three times the recharge to ground water. Ground-water levels closely tracked marsh water levels indicating a strong hydraulic connection between ground water and the marsh. Reduced surface runoff and ground-water availability are stabilizing influences on marsh hydrology and probably contribute to the persistence of emergent vegetation. The rapid hydraulic connection between Little Bean Marsh and ground water indicates that the hydrologic regime of most wetlands along the lower Missouri River is largely a function of the altitude of the marsh bottom relative to the altitude of the water table. More water was lost from the marsh through evapotranspiration (59 percent) than all other pathways combined. This is partially because the transpiration process of abundant macrophytes can greatly contribute to the evapotranspiration above that lost from open water surfaces. Surface outflow accounted for 36 percent and ground-water seepage accounted for only 5 percent of the losses. Large residence times allows the marsh to greatly affect water quality before water escapes as ground-water recharge or surface outflow. The shallowness of Little Bean Marsh and ion exclusion during ice formation caused the highest specific conductances of 1,100 to 1,300 microsiemens per centimeter at 25 degrees Celsius to occur during the winter. This concentration of dissolved solutes under ice can make wetlands more vulnerable to toxic contaminants than deeper surface-water bodies. Dissolved oxygen was less than 5 mg/L (milligrams per liter) for 3 to 4 months and near 0 mg/L for about 1 month in summer. Despite depths of less than 1 meter, temperature stratification persisted more than 3 months during the summers of 1996 and 1997, preventing mixing and contributing to periods of anoxia. Shallow depths and extended periods of anoxia in the marsh limit the ability of some organisms to escape high-temperature stress. Turbidity in Little Bean Marsh usually was low for several reasons: sediment loadings from the largely flood-plain drainage were low, emergent vegetation shade out algae and shield the water from wind, and high concentrations of bivalent cations increase flocculation rates of inorganic suspended material. The high concentrations of bivalent cations was largely because of a substantial amount of ground-water seepage into the marsh. Dissolved organic nitrogen was the dominant nitrogen species in Little Bean Marsh. Denitrification and biotic uptake kept more than 62 percent of nitrate (NO3) and 43 percent of ammonium (NH4) concentrations in marsh samples less than a detection limit of 0.005 mg/L. This contrasts with the Missouri River where inorganic NO3 dominates. Consequently, artificial flood-plain drainage that bypasses riparian wetlands likely deliver substantially more biotically available inorganic nitrogen to receiving waters than surface water that has been routed through a remnant wetland. Average total nitrogen concentrations in Little Bean Marsh were substantially less than those at other Missouri River wetlands, roughly one-half the mean concentrations in the Missouri River, but roughly twice the average nitrogen values in reservoirs of the glaciated plains of Missouri. The largest concentrations of nearly all species of nitrogen and phosphorus and the most intense period of hypereutrophy coincided with a phytoplankton bloom and senescence of River Bulrush (Scirpus fluviatilis) and common cattail (Typha latifolia) in September 1997. The rapid leaching of nitrogen that occurs soon after macrophyte senescence combined with a recent destratification of the marsh probably provided nitrogen to the nitrogen-limited open-water areas and triggered a phytoplankton bloom. Despite the rarity of runoff events, surface runoff from the watershed, combined with atmospheric deposition, contributed more than seven times the 530 kg (kilograms) of nitrogen that escaped Little Bean Marsh in surface outflow during 1997. Atmospheric deposition alone was more than 530 kg. Seepage to ground water contained less than 1.5 percent of the nitrogen leaving the marsh in surface outflow. The slow decay rate of Scirpus fluviatilis and reducing conditions in bottom sediments make burial of organic nitrogen a substantial sink of nitrogen. Denitrification experiments indicate that denitrification rates were limited by NO3 in the water column. Consequently, decomposition and nitrification of NH4 and organic nitrogen are the rate limiting steps of nitrogen removal in Little Bean Marsh. The NO3-limited rates of denitrification also indicate that Little Bean Marsh has a large unused capacity for nitrogen removal. These data indicate that the vast extent of riparian marshes along the Missouri and Mississippi Rivers may have had a substantial role in limiting NO3 loads to the Gulf of Mexico before agricultural development of flood plains. Drainage and removal of riparian marshes may be a major cause of the increased NO3 loads to the Gulf of Mexico. Periods of anoxia had much larger effects on phosphorus release than the other variables. The largest concentrations of phosphorus occurred in late summer and corresponded with senescing macrophytes, periods of anoxia, and a large algal bloom in Little Bean Marsh. Low water levels prevented the escape of phosphorus in surface outflow during these periods of highest phosphorus concentrations. Dry weather in late summer is typical and probably makes the correspondence of low water levels, anoxia, and consequent low phosphorus release a common occurrence in marshes along the Missouri River. Little Bean Marsh retained more than 95 percent of the phosphorus it received. The amount of phosphorus in surface inflows to the marsh were more than one order of magnitude greater than that escaping in surface outflows. The long hydraulic residence time of the marsh and large contributions of iron from ground water (that provide many sorption sites for phosphorus) make the marsh an effective sediment and phosphorus trap.

Missouri↗
USGS2006

County-level estimates of nutrient inputs to the land surface of the conterminous United States, 1982-2001

Nutrient input data for fertilizer use, livestock manure, and atmospheric deposition from various sources were estimated and allocated to counties in the conterminous United States for the years 1982 through 2001. These nationally consistent nutrient input data are needed by the National Water-Quality Assessment Program for investigations of stream- and ground-water quality. For nitrogen, the largest source was farm fertilizer; for phosphorus, the largest sources were farm fertilizer and livestock manure. Nutrient inputs from fertilizer use in nonfarm areas, while locally important, were an order of magnitude smaller than inputs from other sources. Nutrient inputs from all sources increased between 1987 and 1997, but the relative proportions of nutrients from each source were constant. Farm-fertilizer inputs were highest in the upper Midwest, along eastern coastal areas, and in irrigated areas of the West. Nonfarm-fertilizer use was similar in major metropolitan areas throughout the Nation, but was more extensive in the more populated Eastern and Central States and in California. Areas of greater manure inputs were located throughout the South-central and Southeastern States and in scattered areas of the West. Nitrogen deposition from the atmosphere generally increased from west to east and is related to the location of major sources and the effects of precipitation and prevailing winds. These nutrient-loading data at the county level are expected to be the fundamental basis for national and regional assessments of water quality for the National Water-Quality Assessment Program and other large-scale programs.

conterminous United States↗
USGS2006

StreamVOC - A deterministic source-apportionment model to estimate volatile organic compound concentrations in rivers and streams

This report documents the construction and verification of the model, StreamVOC, that estimates (1) the time- and position-dependent concentrations of volatile organic compounds (VOCs) in rivers and streams as well as (2) the source apportionment (SA) of those concentrations. The model considers how different types of sources and loss processes can act together to yield a given observed VOC concentration. Reasons for interest in the relative and absolute contributions of different sources to contaminant concentrations include the need to apportion: (1) the origins for an observed contamination, and (2) the associated human and ecosystem risks. For VOCs, sources of interest include the atmosphere (by absorption), as well as point and nonpoint inflows of VOC-containing water. Loss processes of interest include volatilization to the atmosphere, degradation, and outflows of VOC-containing water from the stream to local ground water. This report presents the details of StreamVOC and compares model output with measured concentrations for eight VOCs found in the Aberjona River at Winchester, Massachusetts. Input data for the model were obtained during a synoptic study of the stream system conducted July 11-13, 2001, as part of the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey. The input data included a variety of basic stream characteristics (for example, flows, temperature, and VOC concentrations). The StreamVOC concentration results agreed moderately well with the measured concentration data for several VOCs and provided compound-dependent SA estimates as a function of longitudinal distance down the river. For many VOCs, the quality of the agreement between the model-simulated and measured concentrations could be improved by simple adjustments of the model input parameters. In general, this study illustrated: (1) the considerable difficulty of quantifying correctly the locations and magnitudes of ground-water-related sources of contamination in streams; and (2) that model-based estimates of stream VOC concentrations are likely to be most accurate when the major sources are point sources or tributaries where the spatial extent and magnitude of the sources are tightly constrained and easily determined.

Scientific Investigations Report↗
USGS2006

Organochlorine compounds and current-use pesticides in snow and lake sediment in Rocky Mountain National Park, Colorado, and Glacier National Park, Montana, 2002-03

Organochlorine compounds and current-use pesticides were measured in snow and lake-sediment samples from Rocky Mountain National Park in Colorado and Glacier National Park in Montana to determine their occurrence and distribution in high-elevation aquatic ecosystems. The U.S. Geological Survey, in cooperation with the National Park Service, collected snow samples at eight sites in Rocky Mountain National Park and at eight sites in Glacier National Park during spring of 2002 and 2003 just prior to the start of snowmelt. Surface sediments were collected from 11 lakes in Rocky Mountain National Park and 10 lakes in Glacier National Park during summer months of 2002 and 2003. Samples were analyzed for organochlorine compounds by gas chromatography with electron-capture detection and current-use pesticides by gas chromatography with electron-impact mass spectrometry. A subset of samples was reanalyzed using a third instrumental technique (gas chromatography with electron-capture negative ion mass spectrometry) to verify detected concentrations in the initial analysis and to investigate the presence of additional compounds. For the snow samples, the pesticides most frequently detected were endosulfan, dacthal, and chlorothalonil, all of which are chlorinated pesticides that currently are registered for use in North America. Concentrations of these pesticides in snow were very low, ranging from 0.07 to 2.36 nanograms per liter. Of the historical-use pesticides, hexachlorobenzene, dieldrin, and trans -nonachlor were detected in snow but only in one sample each. Annual deposition rates of dacthal, endosulfan, and chlorothalonil were estimated at 0.7 to 3.0 micrograms per square meter. These estimates are likely biased low because they do not account for pesticide deposition during summer months. For the lake-sediment samples, DDE ( p,p’ -dichlorodiphenyldichoroethene) and DDD ( p,p’ -dichlorodiphenyldichoroethane) were the most frequently detected organochlorine compounds. DDE and DDD are degradation products of DDT ( p,p’ -dichlorodiphenyltrichloroethane), which is a well-documented, persistent organochlorine insecticide that has been banned from use in the United States since 1972. Detected concentrations were very low, ranging from 0.12 to 4.7 micrograms per kilogram, and probably pose little threat to aquatic organisms in park lakes. DDD and DDE concentrations in a sediment core from Mills Lake in Rocky Mountain National Park indicate that atmospheric deposition of DDT and possibly other banned organochlorine compounds to high-elevation parks has been in decline since the 1970s. Commonly detected current-use pesticides in lake sediments included dacthal and endosulfan sulfate, which ranged in concentrations from 0.11 to 0.26 micrograms per kilogram for dacthal and 0.12 to 1.2 micrograms per kilogram for endosulfan sulfate. Both compounds were found in nearly all the snow samples, confirming that some current-use pesticides entering high-elevation aquatic ecosystems through atmospheric deposition are accumulating in lake sediments and potentially in aquatic biota.

Colorado, Montana↗
USGS2007

Mapping Evapotranspiration Units in the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah

Accurate estimates of ground-water discharge are crucial in the development of a water budget for the Basin and Range carbonate-rock aquifer system study area. One common method used throughout the southwestern United States is to estimate ground-water discharge from evapotranspiration (ET). ET is a process by which water from the Earth's surface is transferred to the atmosphere. The volume of water lost to the atmosphere by ET can be computed as the product of the ET rate and the acreage of vegetation, open water, and moist soil through which ET occurs. The procedure used in the study groups areas of similar vegetation, water, and soil conditions into different ET units, assigns an average annual ET rate to each unit, and computes annual ET from each ET unit within the outer extent of potential areas of ground-water discharge. Data sets and the procedures used to delineate the ET-unit map used to estimate ground-water discharge from the study area and a qualitative assessment of the accuracy of the map are described in this report.

Scientific Investigations Report↗
USGS2007

Nutrient Enrichment in Estuaries from Discharge of Shallow Ground Water, Mt. Desert Island, Maine

Nutrient enrichment from atmospheric deposition, agricultural activities, wildlife, and domestic sources is a concern at Acadia National Park because of the potential problem of water-quality degradation and eutrophication in its estuaries. Water-quality degradation has been observed at the Park?s Bass Harbor Marsh estuary but not in Northeast Creek estuary. Previous studies at Acadia National Park have estimated nutrient inputs to estuaries from atmospheric deposition and surface-water runoff, but the importance of shallow ground water that may contain nutrients derived from domestic or other sources is unknown. Northeast Creek and Bass Harbor Marsh estuaries were studied to (1) identify shallow ground-water seeps, (2) assess the chemistry of the water discharged from selected seeps, and (3) assess the chemistry of ground water in shallow ground-water hyporheic zones. The hyporheic zone is defined here as the region beneath and lateral to a stream bed, where there is mixing of shallow ground water and surface water. This study also provides baseline chemical data for ground water in selected bedrock monitoring wells and domestic wells on Mt. Desert Island. Water samples were analyzed for concentrations of nutrients, wastewater compounds, dissolved organic carbon, pH, dissolved oxygen, temperature and specific conductance. Samples from bedrock monitoring wells also were analyzed for alkalinity, major cations and anions, and trace metals. Shallow ground-water seeps to Northeast Creek and Bass Harbor Marsh estuaries at Acadia National Park were identified and georeferenced using aerial infrared digital imagery. Monitoring included the deployment of continuously recording temperature and specific conductance sensors in the seep discharge zone to access marine or freshwater signatures related to tidal flooding, gradient-driven shallow ground-water flow, or shallow subsurface flow related to precipitation events. Many potential shallow ground-water discharge zones were identified from aerial thermal imagery during flights in May and December 2003 in both estuaries. The occurrence of ground-water seeps was confirmed using continuous and discrete measurements of temperature and specific conductance in selected seeps and in the adjacent estuaries that showed salinity anomalies reflecting the input of freshwater in these complex tidal systems. Analysis of water samples from shallow ground water in the hyporheic zone and from ground-water seeps indicated the presence of elevated concentrations of dissolved nitrogen, compared to concentrations in the adjacent estuaries and surface-water tributaries draining into the estuaries. These findings indicate that shallow ground water is a source of dissolved nitrogen to the estuaries. Orthophosphate levels were low in ground water in the hyporheic zone in Bass Harbor Marsh, but somewhat higher in one hyporheic-zone well in Northeast Creek compared with the concentrations in both estuaries that were at or below detection limits. Household wastewater-related compounds were not detected in ground water in the hyporheic zone. Analysis of water samples from domestic and bedrock monitoring wells developed in fractured bedrock indicated that concentrations of dissolved nitrogen, phosphorus, and household wastewater-related compounds were typically at or below detection, suggesting that the aquifers sampled had not been contaminated from septic sources.

Scientific Investigations Report↗
USGS2009

Hydrogeologic Framework of the Yakima River Basin Aquifer System, Washington

The Yakima River basin aquifer system underlies about 6,200 square miles in south-central Washington. The aquifer system consists of basin-fill deposits occurring in six structural-sedimentary basins, the Columbia River Basalt Group (CRBG), and generally older bedrock. The basin-fill deposits were divided into 19 hydrogeologic units, the CRBG was divided into three units separated by two interbed units, and the bedrock was divided into four units (the Paleozoic, the Mesozoic, the Tertiary, and the Quaternary bedrock units). The thickness of the basin-fill units and the depth to the top of each unit and interbed of the CRBG were mapped. Only the surficial extent of the bedrock units was mapped due to insufficient data. Average mapped thickness of the different units ranged from 10 to 600 feet. Lateral hydraulic conductivity (Kh) of the units varies widely indicating the heterogeneity of the aquifer system. Average or effective Kh values of the water-producing zones of the basin-fill units are on the order of 1 to 800 ft/d and are about 1 to 10 ft/d for the CRBG units as a whole. Effective or average Kh values for the different rock types of the Paleozoic, Mesozoic, and Tertiary units appear to be about 0.0001 to 3 ft/d. The more permeable Quaternary bedrock unit may have Kh values that range from 1 to 7,000 ft/d. Vertical hydraulic conductivity (Kv) of the units is largely unknown. Kv values have been estimated to range from about 0.009 to 2 ft/d for the basin-fill units and Kv values for the clay-to-shale parts of the units may be as small as 10-10 to 10-7 ft/d. Reported Kv values for the CRBG units ranged from 4x10-7 to 4 ft/d. Variations in the concentrations of geochemical solutes and the concentrations and ratios of the isotopes of hydrogen, oxygen, and carbon in groundwater provided information on the hydrogeologic framework and groundwater movement. Stable isotope ratios of water (deuterium and oxygen-18) indicated dispersed sources of groundwater recharge to the CRBG and basin-fill units and that the source of surface and groundwater is derived from atmospheric precipitation. The concentrations of dissolved methane were larger than could be attributable to atmospheric sources in more than 80 percent of wells with measured methane concentrations. The concentrations of the stable isotope of carbon-13 of methane were indicative of a thermogenic source of methane. Most of the occurrences of methane were at locations several miles distant from mapped structural fault features, suggesting the upward vertical movement of thermogenic methane from the underlying bedrock may be more widespread than previously assumed or there may be a more general occurrence of unmapped (buried) fault structures. Carbon and tritium isotope data and the concentrations of dissolved constituents indicate a complex groundwater flow system with multiple contributing zones to groundwater wells and relative groundwater residence time on the order of a few tens to many thousands of years. Potential mean annual recharge for water years 1950-2003 was estimated to be about 15.6 in. or 7,149 ft3/s (5.2 million acre-ft) and includes affects of human activities such as irrigation of croplands. If there had been no human activities (predevelopment conditions) during that time period, estimated recharge would have been about 11.9 in. or 5,450 ft3/s (3.9 million acre-ft). Estimated mean annual recharge ranges from virtually zero in the dry parts of the lower basin to more than 100 in. in the humid uplands, where annual precipitation is more than 120 in. Groundwater in the different hydrogeologic units occurs under perched, unconfined, semiconfined, and confined conditions. Groundwater moves from topographic highs in the uplands to topographic low areas along the streams. The flow system in the basin-fill units is compartmentalized due to topography and geologic structure. The flow system also is compartmentalized for the CRBG units but not to as large

Scientific Investigations Report↗
USGS2010

Development and Application of Regression Models for Estimating Nutrient Concentrations in Streams of the Conterminous United States, 1992-2001

Data collected for the U.S. Geological Survey National Water-Quality Assessment program from 1992-2001 were used to investigate the relations between nutrient concentrations and nutrient sources, hydrology, and basin characteristics. Regression models were developed to estimate annual flow-weighted concentrations of total nitrogen and total phosphorus using explanatory variables derived from currently available national ancillary data. Different total-nitrogen regression models were used for agricultural (25 percent or more of basin area classified as agricultural land use) and nonagricultural basins. Atmospheric, fertilizer, and manure inputs of nitrogen, percent sand in soil, subsurface drainage, overland flow, mean annual precipitation, and percent undeveloped area were significant variables in the agricultural basin total nitrogen model. Significant explanatory variables in the nonagricultural total nitrogen model were total nonpoint-source nitrogen input (sum of nitrogen from manure, fertilizer, and atmospheric deposition), population density, mean annual runoff, and percent base flow. The concentrations of nutrients derived from regression (CONDOR) models were applied to drainage basins associated with the U.S. Environmental Protection Agency (USEPA) River Reach File (RF1) to predict flow-weighted mean annual total nitrogen concentrations for the conterminous United States. The majority of stream miles in the Nation have predicted concentrations less than 5 milligrams per liter. Concentrations greater than 5 milligrams per liter were predicted for a broad area extending from Ohio to eastern Nebraska, areas spatially associated with greater application of fertilizer and manure. Probabilities that mean annual total-nitrogen concentrations exceed the USEPA regional nutrient criteria were determined by incorporating model prediction uncertainty. In all nutrient regions where criteria have been established, there is at least a 50 percent probability of exceeding the criteria in more than half of the stream miles. Dividing calibration sites into agricultural and nonagricultural groups did not improve the explanatory capability for total phosphorus models. The group of explanatory variables that yielded the lowest model error for mean annual total phosphorus concentrations includes phosphorus input from manure, population density, amounts of range land and forest land, percent sand in soil, and percent base flow. However, the large unexplained variability and associated model error precluded the use of the total phosphorus model for nationwide extrapolations.

Scientific Investigations Report↗
USGS2010

Comparison of mercury in water, bottom sediment, and zooplankton in two Front Range reservoirs in Colorado, 2008-09

The U.S. Geological Survey, in cooperation with the Colorado Department of Public Health and Environment, conducted a study to investigate environmental factors that may contribute to the bioaccumulation of mercury in two Front Range reservoirs. One of the reservoirs, Brush Hollow Reservoir, currently (2009) has a fish-consumption advisory for mercury in walleye (Stizostedion vitreum), and the other, Pueblo Reservoir, which is nearby, does not. Water, bottom sediment, and zooplankton samples were collected during 2008 and 2009, and a sediment-incubation experiment was conducted in 2009. Total mercury concentrations were low in midlake water samples and were not substantially different between the two reservoirs. The only water samples with detectable methylmercury were collected in shallow areas of Brush Hollow Reservoir during spring. Mercury concentrations in reservoir bottom sediments were similar to those reported for stream sediments from unmined basins across the United States. Despite higher concentrations of fish-tissue mercury in Brush Hollow Reservoir, concentrations of methylmercury in sediment were as much as 3 times higher in Pueblo Reservoir. Mercury concentrations in zooplankton were at the low end of concentrations reported for temperate lakes in the Northeastern United States and were similar between sites, which may reflect the seasonal timing of sampling. Factors affecting bioaccumulation of mercury were assessed, including mercury sources, water quality, and reservoir characteristics. Atmospheric deposition was determined to be the dominant source of mercury; however, due to the proximity of the reservoirs, atmospheric inputs likely are similar in both study areas. Water-quality constituents commonly associated with elevated concentrations of mercury in fish (pH, alkalinity, sulfate, nutrients, and dissolved organic carbon) did not appear to explain differences in fish-tissue mercury concentrations between the reservoirs. Low methylmercury concentrations in hypolimnetic water indicate low potential for increased methylmercury production following the development of anoxic conditions in summer. Based on the limited dataset, water-level fluctuations and shoreline characteristics appear to best explain differences in fish-tissue mercury concentrations between the reservoirs. Due to the shallow depth and the large annual water-level fluctuations at Brush Hollow Reservoir, proportionally larger areas of shoreline at Brush Hollow Reservoir are subjected to annual reflooding compared to Pueblo Reservoir. Moreover, presence of macrophyte beds and regrowth of terrestrial vegetation likely increase the organic content of near-shore sediments in Brush Hollow Reservoir, which may stimulate methylmercury production in littoral areas subject to reflooding. Results of a laboratory incubation experiment were consistent with this hypothesis.

Colorado↗
USGS2012

Estimates of tracer-based piston-flow ages of groundwater from selected sites: National Water-Quality Assessment Program, 2006-2010

Piston-flow age dates were interpreted from measured concentrations of environmental tracers from 812 National Water-Quality Assessment (NAWQA) Program groundwater sites from 27 Study Units across the United States. The tracers of interest include chlorofluorocarbons (CFCs), sulfur hexafluoride (SF 6 ), and tritium/helium-3 ( 3 H/ 3 He). Tracer data compiled for this analysis were collected from 2006 to 2010 from groundwater wells in NAWQA studies, including: * Land-Use Studies (LUS, shallow wells, usually monitoring wells, located in recharge areas under dominant land-use settings), * Major-Aquifer Studies (MAS, wells, usually domestic supply wells, located in principal aquifers and representing the shallow drinking water supply), * Flow System Studies (FSS, networks of clustered wells located along a flowpath extending from a recharge zone to a discharge zone, preferably a shallow stream) associated with Land-Use Studies, and * Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) also associated with Land-Use Studies. Tracer data were evaluated using documented methods and are presented as aqueous concentrations, equivalent atmospheric concentrations (for CFCs and SF 6 ), and tracer-based piston-flow ages. Selected ancillary data, such as redox data, well-construction data, and major dissolved-gas (N 2 , O 2 , Ar, CH 4 , and CO 2 ) data, also are presented. Recharge temperature was inferred using climate data (approximated by mean annual air temperature plus 1°C [MAAT +1°C]) as well as major dissolved-gas data (N 2 -Ar-based) where available. The N 2 -Ar-based temperatures showed significantly more variation than the climate-based data, as well as the effects of denitrification and degassing resulting from reducing conditions. The N 2 -Ar-based temperatures were colder than the climate-based temperatures in networks where recharge was limited to the winter months when evapotranspiration was reduced. The tracer-based piston-flow ages compiled in this report are provided as a consistent means of reporting the tracer data. The tracer-based piston-flow ages may provide an initial interpretation of age in cases in which mixing is minimal and may aid in developing a basic conceptualization of groundwater age in an aquifer. These interpretations are based on the assumption that tracer transport is by advection only and that no mixing occurs. In addition, it is assumed that other uncertainties are minimized, including tracer degradation, sorption, contamination, or fractionation, and that terrigenic (natural) sources of tracers, and spatially variable atmospheric tracer concentrations are constrained.

Scientific Investigations Report↗
USGS2012

Ambient and potential denitrification rates in marsh soils of Northeast Creek and Bass Harbor Marsh watersheds, Mount Desert Island, Maine

Nutrient enrichment from atmospheric deposition, agricultural activities, wildlife, and domestic sources is a concern at Acadia National Park on Mount Desert Island, Maine, because of the potential problems of degradation of water quality and eutrophication in estuaries. Degradation of water quality has been observed at Bass Harbor Marsh estuary in the park but only minimally in Northeast Creek estuary. Previous studies at Acadia National Park have estimated nutrient inputs to estuaries from atmospheric deposition and surface-water runoff, and have identified shallow groundwater as an additional potential source of nutrients. Previous studies at Acadia National Park have assumed that a certain fraction of the nitrogen input was removed through microbial denitrification, but rates of denitrification (natural or maximum potential) in marsh soils have not been determined. The U.S. Geological Survey, in cooperation with Acadia National Park, measured in-place denitrification rates in marsh soils in Northeast Creek and in Bass Harbor Marsh watersheds during summer 2008 and summer 2009. Denitrification was measured under ambient conditions as well as after additions of inorganic nitrogen and glucose. In-place denitrification rates under ambient conditions were similar to those reported for other coastal wetlands, although they were generally lower than those reported for salt marshes having high ambient concentrations of nitrate (NO 3 ). Denitrification rates generally increased by at least an order of magnitude following NO 3 additions, with or without glucose (as the carbohydrate) additions, compared with the ambient treatments that received no nutrient additions. The treatment that added both glucose and NO 3 resulted in a variety of denitrification responses when compared with the addition of NO 3 alone. In most cases, the addition of glucose to a given rate of NO3 addition resulted in higher rates of denitrification. These variable responses indicate that the amount of labile carbohydrates can limit denitrification even if NO 3 is present. For most sites in both watersheds, the maximum denitrification rates ranged from of 150 to 900 micromoles of nitrous oxide per square meter per hour. These rates were equivalent to the release of 37 to 221 grams of nitrogen per square meter per year. Weak positive correlations were observed for soil temperature and for measured ammonium concentration in groundwater. Weak negative correlations were observed between denitrification rate and water level and specific conductance. The rates of denitrification in Bass Harbor Marsh and Northeast Creek under ambient conditions, both of which were relatively low, indicate that NO 3 availability is low in both systems. It is evident from the addition of combined treatments of NO 3 and glucose that these marsh soils are capable of comparatively high rates of denitrification, therefore, estuarine eutrophication is not a result of nitrogen inputs to marsh soils that are in excess of the denitrification capacity in these systems. If terrestrial inputs to the estuary are the cause of the observed eutrophic condition in Bass Harbor Marsh, then these inputs to the estuary must bypass the marsh in channelized surface flow, or perhaps they circumvent the marsh in shallow groundwater seepage along subsurface pathways that enter the estuary directly.

Maine↗