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USGS2012

Water-quality characteristics of Michigan's inland lakes, 2001-10

The U.S. Geological Survey and the Michigan Department of Environmental Quality (MDEQ) jointly monitored for selected water-quality constituents and properties of inland lakes during 2001–10 as part of Michigan's Lake Water-Quality Assessment program. During 2001–10, 866 lake basins from 729 inland lakes greater than 25 acres were monitored for baseline water-quality conditions and trophic status. This report summarizes the water-quality characteristics and trophic conditions of the monitored lakes throughout the State; the data include vertical-profile measurements, nutrient measurements at three discrete depths, Secchi-disk transparency (SDT) measurements, and chlorophyll a measurements for the spring and summer, with major ions and other chemical indicators measured during the spring at mid-depth and color during the summer from near-surface samples. In about 75 percent of inland lake deep basins (index stations), trophic characteristics were associated with oligotrophic or mesotrophic conditions; 5 percent or less were categorized as hypereutrophic, and 80 percent of hypereutrophic lakes had a maximum depth of 30 feet or less. Comparison of spring and summer measurements shows that water clarity based on SDT measurements were clearer in the spring than in the summer for 63 percent of lakes. For near-surface measurements made in spring, 97 percent of lakes can be considered phosphorus limited and less than half a percent nitrogen limited; for summer measurements, 96 percent of lakes can be considered phosphorus limited and less than half a percent nitrogen limited. Spatial patterns of major ions, alkalinity, and hardness measured in the spring at mid-depth all showed lower values in the Upper Peninsula of Michigan and a southward increase toward the southern areas of the Lower Peninsula, though the location of increase varied by constituent. A spatial analysis of the data based on U.S. Environmental Protection Agency Level III Ecoregions separated potassium, sulfate, and chloride concentrations fairly well, with a pattern of lower values in northern ecoregions trending toward higher values in southern ecoregions; lower and higher concentrations of magnesium, hardness, calcium, and alkalinity were well separated, but middle-range concentrations in central Michigan ecoregions were mixed. The highest concentrations of chloride and sodium were in the southeastern area of the Lower Peninsula. Lakes with multiple basins showed few statistically significant differences in constituent concentrations at the 95-percent confidence level among combinations of depths between basins. The most statistically significant differences were found for water temperature, with significant differences in somewhat less than half the combinations in the spring and just a few combinations in the summer. The lack of significant differences between major basins of multibasin lakes indicates that monitoring of trophic characteristics in all major basins might not be necessary for the majority of constituents in future sampling programs. Trophic characteristics based on the 2001–10 dataset were compared to trophic characteristics resulting from other Michigan sampling programs, including the volunteer Cooperative Lakes Monitoring Program coordinated by the MDEQ (measurements on 250 lakes in 2011), trophic-state predictions produced by relating existing measurements to remotely sensed data (measurements for about 3,000 lakes), and the National Lakes Assessment (NLA) statistically valid, probability-designed lakes program (measurements for 50 lakes in Michigan and about 1,100 lakes nationally). A higher percentage of oligotrophic lakes resulted when using SDT from the volunteer data and the 2001–10 dataset than when using the predicted measurements from remotely sensed data or the NLA. Comparing trophic characteristics from differently designed programs provides multiple interpretations of lake water-quality status in Michigan lakes. No directional statistically significant difference was found at the 95-percent confidence level among historical nutrients and trophic characteristics when comparing 445 lakes with historical data for 1974–84 with the 2001–10 dataset, though SDT did show statistically significant differences at the 95-percent confidence level. Depending on the primary indicator, 50–66 percent of lakes did not change trophic-status class, 13–23 percent moved towards the oligotrophic end of the TSI scale, and 20–25 percent moved a class towards the eutrophic end of the TSI scale. Increasing percentages of urban-dominant land cover in the drainage areas of lakes had a more positive correlation with chloride concentration than did increased percentages of other land-cover classes; there was also a slight correlation of urban-dominant land cover and calcium concentration. Removing data for lakes in southeastern Lower Michigan, known from previous reports to be higher in chloride, still resulted in a positive relation even though the coefficient of determination (R 2 value) decreased from 0.55 to 0.39. Dominant land-cover drainage areas were not strongly related to nutrients with respect to a linear relation, nor were lake drainage-area sizes.

Michigan↗

USGS2017

Maps and grids of hydrogeologic information created from standardized water-well drillers’ records of the glaciated United States

As part of the National Water Availability and Use Program established by the U.S. Geological Survey (USGS) in 2005, this study took advantage of about 14 million records from State-managed collections of water-well drillers’ records and created a database of hydrogeologic properties for the glaciated United States. The water-well drillers’ records were standardized to be relatively complete and error-free and to provide consistent variables and naming conventions that span all State boundaries. Maps and geospatial grids were developed for (1) total thickness of glacial deposits, (2) total thickness of coarse-grained deposits, (3) specific-capacity based transmissivity and hydraulic conductivity, and (4) texture-based estimated equivalent horizontal and vertical hydraulic conductivity and transmissivity. The information included in these maps and grids is required for most assessments of groundwater availability, in addition to having applications to studies of groundwater flow and transport. The texture-based estimated equivalent horizontal and vertical hydraulic conductivity and transmissivity were based on an assumed range of hydraulic conductivity values for coarse- and fine-grained deposits and should only be used with complete awareness of the methods used to create them. However, the maps and grids of texture-based estimated equivalent hydraulic conductivity and transmissivity may be useful for application to areas where a range of measured values is available for re-scaling. Maps of hydrogeologic information for some States are presented as examples in this report but maps and grids for all States are available electronically at the project Web site (USGS Glacial Aquifer System Groundwater Availability Study, http://mi.water.usgs.gov/projects/WaterSmart/Map-SIR2015-5105.html ) and the Science Base Web site, https://www.sciencebase.gov/catalog/item/58756c7ee4b0a829a3276352 .

Alaska, Connecticut, Idaho, Illinois, Indiana, Iow↗

USGS2025

Potential risks of vegetation treatments to introduce and increase invasive annual grasses in rangelands of Montana, North Dakota, and South Dakota— A science synthesis to inform National Environmental Policy Act analyses

The U.S. Geological Survey is working with Federal land management agencies to develop a series of planned structured science syntheses to support environmental effects analyses that agencies conduct under the National Environmental Policy Act (NEPA). This report synthesizes science information relevant to environmental effects analyses concerned with potential increases in the distribution and abundance of invasive annual grasses (IAGs) from proposed vegetation treatments for habitat restoration. The focal environments for this synthesis are rangelands in the intermontane valleys of Montana and the northern Great Plains of Montana, North Dakota, and South Dakota. The synthesis is organized to align with the standard elements of NEPA analyses and provides information on relevant scientific studies, data availability, analysis methods, and mitigation measures. We found that the likelihood of increasing IAGs from vegetation treatments depends on treatment type and environmental context. In sagebrush ecosystems of the focal region, prescribed fire often reduces or does not increase IAGs. Treatments that cause soil disturbances, such as mechanical removals of sagebrush or firebreak constructions, are more likely to increase IAGs than other treatments. Herbicides applied to reduce sagebrush cover have not increased the proportion of IAGs in the plant community. Temperature and precipitation have been strong factors in determining IAG responses to vegetation treatments in sagebrush ecosystems of the focal region, where more precipitation in spring and summer likely provides a competitive edge to native, perennial grasses more than winter annual grasses like Bromus tectorum L. (cheatgrass). In grasslands, prescribed fire often reduces IAGs, but effects depend on the abundance of native species and are often short lived. Mowing can increase or decrease IAGs in grassland ecosystems. Grassland site conditions, such as southeast-facing slopes, sandier or rockier sites, or lower native species cover or richness affect the likelihood of invasion by annual grasses. Maintaining adequate cover of perennial vegetation creates rangelands that are resistant and resilient to annual grass invasions. Managers can minimize invasion potential by focusing on treatment type, placement, and seasonal timing. Herbicides also can provide effective mitigation, especially in combination with other controls such as prescribed fire or grazing. This report can be incorporated by reference in NEPA documentation, included in a project record, or provide a general reference for understanding and identifying literature about increases in IAGs associated with vegetation treatments in rangelands in this focal region.

Montana, North Dakota, South Dakota↗

USGS2002

Louisiana Ground-Water Map No.13: Hydrogeology and Potentiometric Surface of the Sparta Aquifer in Northern Louisiana, October 1996

This report describes the thickness and areal extent of the Sparta aquifer, identifies sands within the fresh-water extent of the aquifer, and presents data and a map that illustrate the generalized potentiometric surface (water levels) during October 1996. The report includes a detailed geophysical log, structure contour maps, hydrogeologic sections, and hydrographs of water levels in selected wells. The potentiometric surface-map can be used for determining direction of ground-water flow, hydraulic gradients, and the effects of withdrawals on the aquifer.

Water-Resources Investigations Report↗

USGS2002

Louisiana ground-water map no. 13: Hydrogeology and potentiometric surface of the Sparta aquifer in northern Louisiana, October 1996

Louisiana↗

USGS1987

Interlaboratory comparability, bias, and precision for four laboratories measuring analytes in wet deposition, October 1983-December 1984

Four laboratories involved in the routine analysis of wet-deposition samples participated in an interlaboratory comparison program managed by the U.S. Geological Survey. The four participants were: Illinois State Water Survey central analytical laboratory in Champaign, Illinois; U.S. Geological Survey national water-quality laboratories in Atlanta, Georgia, and Denver, Colorado; and Inland Waters Directorate national water-quality laboratory in Burlington, Ontario, Canada. Analyses of interlaboratory samples performed by the four laboratories from October 1983 through December 1984 were compared. Participating laboratories analyzed three types of interlaboratory samples--natural wet deposition, simulated wet deposition, and deionized water--for pH and specific conductance, and for dissolved calcium, magnesium, sodium, sodium, potassium, chloride, sulfate, nitrate, ammonium, and orthophosphate. Natural wet-deposition samples were aliquots of actual wet-deposition samples. Analyses of these samples by the four laboratories were compared using analysis of variance. Test results indicated that pH, calcium, nitrate, and ammonium results were not directly comparable among the four laboratories. Statistically significant differences between laboratory results probably only were meaningful for analyses of dissolved calcium. Simulated wet-deposition samples with known analyte concentrations were used to test each laboratory for analyte bias. Laboratory analyses of calcium, magnesium, sodium, potassium, chloride, sulfate, and nitrate were not significantly different from the known concentrations of these analytes when tested using analysis of variance. Deionized-water samples were used to test each laboratory for reporting of false positive values. The Illinois State Water Survey Laboratory reported the smallest percentage of false positive values for most analytes. Analyte precision was estimated for each laboratory from results of replicate measurements. In general, the Illinois State Water Survey laboratory achieved the greatest precision, whereas the U.S. Geological Survey laboratories achieved the least precision.

Water-Resources Investigations Report↗

USGS2003

Ground-water conditions in Utah, spring of 2003

This is the fortieth in a series of annual reports that describe ground-water conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Department of Natural Resources, Division of Water Resources and Division of Water Rights, provide data to enable interested parties to maintain awareness of changing ground-water conditions. This report, like the others in the series, contains information on well construction, ground-water withdrawal from wells, water-level changes, precipitation, streamflow, and chemical quality of water. Information on well construction included in this report refers only to wells constructed for new appropriations of ground water. Supplementary data are included in reports of this series only for those years or areas which are important to a discussion of changing ground-water conditions and for which applicable data are available. This report includes individual discussions of selected significant areas of ground-water development in the State for calendar year 2002. Most of the reported data were collected by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Water Rights and Division of Water Resources.

Utah↗

USGS2002

Ground-water conditions in Utah, spring of 2002

This is the thirty-ninth in a series of annual reports that describe ground-water conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Department of Natural Resources, Division of Water Resources and Division of Water Rights, provide data to enable interested parties to maintain awareness of changing ground-water conditions. This report, like the others in the series, contains information on well construction, ground-water withdrawal from wells, water-level changes, precipitation, streamflow, and chemical quality of water. Information on well construction included in this report refers only to wells constructed for new appropriations of ground water. Supplementary data are included in reports of this series only for those years or areas which are important to a discussion of changing ground-water conditions and for which applicable data are available. This report includes individual discussions of selected significant areas of ground-water development in the State for calendar year 2001. Most of the reported data were collected by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Water Rights and Division of Water Resources.

Utah↗

USGS2009

Water Budgets for Coeur d'Alene Lake, Idaho, Water Years 2000-2005

The U.S. Geological Survey, in cooperation with the Idaho Department of Water Resources, calculated annual water budgets and a mean annual water budget for Coeur d'Alene Lake, Idaho, for water years 2000 through 2005. Mean annual inflow to Coeur d'Alene Lake, including precipitation, was about 167,110 million cubic feet. Mean annual outflow, including evaporation, but excluding wastewater effluent to the Spokane River, was about 167,850 million cubic feet. The amount of water lost from Coeur d'Alene Lake and the Spokane River to the Spokane Valley-Rathdrum Prairie aquifer was estimated at 7,250 million cubic feet. Mean annual precipitation into Coeur d'Alene Lake was 3,267 million cubic feet, which exceeded mean annual evaporation of 2,483 million cubic feet. Withdrawals directly from the lake and from wells within a 1,000 foot buffer of the lakeshore for domestic and municipal water uses were reported. However, only the estimate for the consumptive use part of the withdrawals, 265 million cubic feet, was considered in the budget. Mean annual change in lake storage resulted in a net loss of about 49 million cubic feet. The mean annual residual value was about -8,310 million cubic feet.

Scientific Investigations Report↗

USGS2011

Effects of natural and human factors on groundwater quality of basin-fill aquifers in the southwestern United States: Conceptual models for selected contaminants

As part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program, the Southwest Principal Aquifers (SWPA) study is building a better understanding of the factors that affect water quality in basin-fill aquifers in the Southwestern United States. The SWPA study area includes four principal aquifers of the United States: the Basin and Range basin-fill aquifers in California, Nevada, Utah, and Arizona; the Rio Grande aquifer system in New Mexico and Colorado; and the California Coastal Basin and Central Valley aquifer systems in California. Similarities in the hydrogeology, land- and water-use practices, and water-quality issues for alluvial basins within the study area allow for regional analysis through synthesis of the baseline knowledge of groundwater-quality conditions in basins previously studied by the NAWQA Program. Resulting improvements in the understanding of the sources, movement, and fate of contaminants are assisting in the development of tools used to assess aquifer susceptibility and vulnerability. This report synthesizes previously published information about the groundwater systems and water quality of 15 information-rich basin-fill aquifers (SWPA case-study basins) into conceptual models of the primary natural and human factors commonly affecting groundwater quality with respect to selected contaminants, thereby helping to build a regional understanding of the susceptibility and vulnerability of basin-fill aquifers to those contaminants. Four relatively common contaminants (dissolved solids, nitrate, arsenic, and uranium) and two contaminant classes (volatile organic compounds (VOCs) and pesticide compounds) were investigated for sources and controls affecting their occurrence and distribution above specified levels of concern in groundwater of the case-study basins. Conceptual models of factors that are important to aquifer vulnerability with respect to those contaminants and contaminant classes were subsequently formed. The conceptual models are intended in part to provide a foundation for subsequent development of regional-scale statistical models that relate specific constituent concentrations or occurrence in groundwater to natural and human factors.

Arizona, California, Colorado, Nevada, New Mexico,↗

USGS1982

Hydrogeologic and water-quality characteristics of the Ironton-Galesville aquifer, southeast Minnesota

Quality of water in the Ironton-Galesville aquifer is generally acceptable for all kinds of uses. Calcium magnesium bicarbonate type water is most common. The dissolved-solids concentration ranges from about 200 to 1,000 milligrams per liter. The lowest values are in the northern part of the aquifer, where the bedrock is at or close to land surface, and the lowest ones are in the southwestern part, where leakage into the aquifer from overlying Cretaceous deposits is highly mineralized water. The concentrations of the major ions, except for bicarbonate and chloride, also increase toward the southwest. Confining beds protect the aquifer from surface pollutants, but high sulfate and iron concentrations and hardness degrade water quality locally in some places. The aquifer was deposited from Paleozoic seas that occupied a shallow depression known as the Hollandale embayment. The surface of the Ironton-Galesville aquifer dips toward the interior of the embayment. The aquifer is as deep as 1,000 feet below land surface and as thick as 325 feet. The Ironton and Galesville Sandstones are both white and medium grained. The aquifer is used mainly in the northern and western parts of the study area, where it is the uppermost bedrock aquifer, This report is one of a series on the hydrogeology and water quality of the 14 principal aquifers in Minnesota prepared by the U.S. Geological Survey. The U.S. Environmental Protection Agency requested these studies because of the need for information to develop its Underground Injection Control Program.

Minnesota↗

USGS1983

Hydrogeologic and water-quality characteristics of the Mount Simon-Hinckley aquifer, southeast Minnesota

The Mount Simon-Hinckley aquifer in southeast Minnesota consists of a thick sequence of sandstone that generally yields large quantities of good-quality water to wells. The aquifer is most important as a source of water supply in the Twin Cities area, where it supplies approximately 10 percent of the ground water used. It is the uppermost bedrock aquifer and, locally, the principal source of domestic supply where it is present north of the Twin Cities. Yield to wells are generally about 500 gallons per minute but may be as high as 2,000 gallons per minute. The aquifer is a good potential source of water because of (1) large quantities of water in storage, (2) adequate yields to wells, and (3) good water quality. The quality of water in the aquifer is generally acceptable for municipal, industrial, and domestic uses. The dissolved-solids concentration in water from the aquifer ranges from a minimum of 48 milligrams per liter to a maximum of 2,810 milligrams per liter. The lowest values are in the eastern and northern parts of the aquifer, where bedrock is at or close to land surface. The highest concentrations are in the southwestern part of the aquifer, where leakage from over lying Cretaceous rocks is highly mineralized water. Magnesium and sulfate concentrations are also high in the southwest. The dissolved-solids concentration generally increases with depth in the aquifer. The predominant water type in the aquifer is calcium magnesium bicarbonate, although sodium chloride waters are present at depth and in the discharge areas along large rivers. This report is one of a series of the hydrogeology and water quality of the 14 principal aquifers in Minnesota prepared by the U.S. Geological Survey. The U.S. Environmental Protection Agency requested these studies because of the need for information to develop its Underground Injection Control Program.

Minnesota↗

USGS1986

Statistical analyses of flood frequency, low-flow frequency, and flow duration of streams in the Philadelphia Area, Pennsylvania

Flood frequency, low-flow frequency, and flow-duration characteristics were computed for 26 stream-gaging stations in and near Philadelphia. Data were obtained from 21 continuous-recording stations and five stations that were initially continuous-recording stations, but which were subsequently converted to crest-stage stations. The annual peak flows were fitted to the three-parameter log-Pearson Type III distribution to develop the flood- frequency characteristics. The range of the reported annual recurrence intervals for flood-frequency depends on record length. Low-flow frequency characteristics for various numbers of consecutive days were also defined by fitting data to the log-Pearson Type III distribution. Standard analyses of daily discharges produced the duration curve characteristics. Results of these analyses are tabulated.

Pennsylvania↗

USGS1996

Occurrence of selenium and mercury in surface water, Wind River Indian Reservation, Wyoming, 1995

Surface-water samples for chemical analyses were collected during May and August 1995 from 13 sites in an irrigated area of the Wind River Federal Irrigation Project, Wind River Indian Reservation, Wyoming. Sites included irrigation drains, ponds, and streams in an irrigated area partially underlain by seleniferous geologic materials described as having the potential to support vegetation that may be toxic to animals. Samples were analyzed for dissolved selenium, mercury, and other inorganic constituents. The study was done in cooperation with the Shoshone Tribe and the Northern Arapaho Tribe. Six samples analyzed from the May sampling period had dissolved selenium concentrations greater than the aquatic-life chronic criterion of 5 μg/L (micrograms per liter) established by the U.S. Environmental Protection Agency (USEPA). The largest dissolved selenium concentration (49 μg/L) exceeded the aquatic-life acute criterion of 20 μg/L established by the USEPA. Selenium concentrations in all 12 samples collected during the August sampling period were less than the laboratory minimum reporting level of 5 μg/L. The Goose Pond Drain site was dry in August. The dissolved solids concentrations were larger in samples collected in May than in August from all but two sites. The large dissolved selenium concentrations in the May samples, collected prior to the start of the irrigation season, were associated with large dissolved solids concentrations. Dissolved mercury concentrations were less than the minimum reporting level of 0.1 jig/L for 24 of the 25 samples collected during May and August. One sample collected in May had a concentration of 0.3 μg/L. This concentration was less than the aquatic-life acute criterion of 2.4 μg/L for mercury established by the USEPA.

Wyoming↗

USGS1983

Developing a state water plan: Ground-water conditions in Utah, spring of 1983

This is the twentieth in a series of annual reports that describe ground-water conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Division of Water Resources, provide data to enable interested parties to keep abreast of changing ground-water conditions. This report, like the others in the series, contains information on well construction, ground-water withdrawals from wells, water-level changes, and related changes in precipitation and streamflow. Supplementary data such as graphs showing chemical quality of water and maps showing ground-water level contours are included in reports of this series only for those years or areas for which applicable data are available and are important to a discussion of changing ground-water conditions. This report includes individual discussions of selected major areas of ground-water development in the State for the calendar year 1982. Water-level fluctuations, however, are described for spring 1982 to spring 1983 and spring 1963 to spring 1983. Much of the data used in this report were collected by the U.S. Geological Survey in cooperation with the Division of Water Rights, Utah Department of Natural Resources.

Utah↗

USGS1987

Developing a state water plan: Ground-water conditions in Utah, spring of 1987

This is the twenty-fourth in a Series of annual reports that describe ground-water Conditions in Utah. Reports in the series, prepared cooperatively by the U.S. Geological Survey and the Utah Division of Water Resources, provide data to enable interested parties to keep abreast of changing ground-water conditions. This report, like the others in the series, contains information on well Construction, ground-water withdrawals from wells, Water-level changes, and related changes in precipitation and streamflow. Supplementary data such as graphs showing chemical quality of Water and maps showing water-level contours are included in reports of this series only for those years or areas for which applicable data are available and are important to a discussion of changing ground-water conditions. The report includes individual discussions of Selected major areas of ground-water development in the State for the calendar year 1986. Water-level fluctuations, however, are described for spring 1986 to spring 1987. Much of the data used in the report were collected by the Geological Survey in cooperation with the Division of Water Rights, Utah Department of Natural Resources.

Utah↗

USGS2010

Effects of including surface depressions in the application of the Precipitation-Runoff Modeling System in the Upper Flint River Basin, Georgia

This report documents an extension of the Precipitation Runoff Modeling System that accounts for the effect of a large number of water-holding depressions in the land surface on the hydrologic response of a basin. Several techniques for developing the inputs needed by this extension also are presented. These techniques include the delineation of the surface depressions, the generation of volume estimates for the surface depressions, and the derivation of model parameters required to describe these surface depressions. This extension is valuable for applications in basins where surface depressions are too small or numerous to conveniently model as discrete spatial units, but where the aggregated storage capacity of these units is large enough to have a substantial effect on streamflow. In addition, this report documents several new model concepts that were evaluated in conjunction with the depression storage functionality, including: ?hydrologically effective? imperviousness, rates of hydraulic conductivity, and daily streamflow routing. All of these techniques are demonstrated as part of an application in the Upper Flint River Basin, Georgia. Simulated solar radiation, potential evapotranspiration, and water balances match observations well, with small errors for the first two simulated data in June and August because of differences in temperatures from the calibration and evaluation periods for those months. Daily runoff simulations show increasing accuracy with streamflow and a good fit overall. Including surface depression storage in the model has the effect of decreasing daily streamflow for all but the lowest flow values. The report discusses the choices and resultant effects involved in delineating and parameterizing these features. The remaining enhancements to the model and its application provide a more realistic description of basin geography and hydrology that serve to constrain the calibration process to more physically realistic parameter values.

Georgia↗

USGS2010

Shallow groundwater quality in the Village of Patchogue, Suffolk County, New York

The onsite disposal of wastewater within the Patchogue River Basin-a riverine estuary that discharges into Great South Bay, Suffolk County, Long Island, N.Y. -has adversely affected water quality and aquatic habitats within both the tidal and non-tidal portions of the river. In response to increased development within the approximately 14 square mile basin, the Village of Patchogue has expanded efforts to manage and protect the local groundwater resources, which sustain freshwater base flow and aquatic habitats. Water-quality samples from 10 shallow wells within the Village were collected in March 2009, before the start of seasonal fertilizer application, to document the effects of onsite wastewater disposal on groundwater discharging into the Patchogue River. Each sample was analyzed for physical properties (pH, dissolved oxygen, specific conductance, and temperature), nutrients, organic carbon, major ions, and trace elements. Water samples from eight wells were analyzed for stable isotopes of nitrogen. The nitrate concentration in one well was 40 milligrams per liter (mg/L), which exceeded the U.S. Environmental Protection Agency (USEPA) and New York State Department of Health (NYSDOH) maximum contamination level in drinking water of 10 mg/L. Sodium concentrations at nine wells exceeded the USEPA Drinking Water Advisory Taste Threshold of 60 mg/L. Dissolved iron concentrations at three wells exceeded the NYSDOH and USEPA Secondary Drinking Water Standard of 300 micrograms per liter (?g/L). Nitrogen isotope signatures (d15N) were determined and compared with those reported from previous studies in Nassau and Suffolk Counties to identify possible sources of the nitrate. Local variations in measured ammonia, nitrate, total nitrogen, phosphorus, and organic carbon concentrations and d15N signatures indicate that nitrate enters the surficial aquifer from several sources (fertilizer, septic waste, and animal waste) and reflects biogeochemical processes such as denitrification.

Scientific Investigations Report↗