Geology topics

James E. Reddy

Publications and source records attributed to James E. Reddy.

At least 19 recordsLinked to original sources

USGS2025

Status of water-quality conditions in the United States, 2010–20

Degradation of water quality can make water harmful or unusable for humans and ecosystems. Although many studies have assessed the effect of individual constituents or narrow suites of constituents on freshwater systems, no consistent, comprehensive assessment exists over the wide range of water-quality effects on water availability. Using published studies, data, and models completed at regional or national scales in the United States during 2010–20, this chapter moves towards a comprehensive assessment by summarizing how selected anthropogenic and geogenic water-quality constituents affect national-scale water availability for human and ecosystem needs. Several types of human health, agricultural, ecological, and beneficial-use standards or thresholds were used to provide context for categorizing surface-water and groundwater quality. Water availability for human and ecological use is limited by elevated concentrations of geogenic and anthropogenic constituents in surface and groundwater. Elevated concentrations of five geogenic constituents (arsenic, manganese, strontium, radium, and adjusted gross alpha) are common in groundwater and collectively affect the drinking water supply to over 30 million people. Surface water sourced drinking water supplies are impaired in about a third of assessed stream miles, most commonly because of non-mercury metals and salinity. Health-based violations at community water systems may disproportionately affect socially vulnerable communities. Ecological water uses are predominantly limited by nutrients, sediment, temperature, pathogens, salinity, and pesticides. Water availability for human and ecological use is adversely affected by human activities including human contaminant sources (for example, wastewater, agriculture), processes (for example, dredging, groundwater pumping), or permanent landscape modifications (for example, dams, urbanization). Primary contaminant sources vary spatially and include fertilizer and manure, atmospheric deposition, wastewater treatment plants, urban land, and a range of natural sources. Contaminants of emerging concern, contaminants without regulatory thresholds, and mixtures of geogenic and anthropogenic water contaminants also contribute to ecological degradation and human exposure.

conterminous United States↗

USGS2024

Isotopic evaluation of the National Water Model reveals missing agricultural irrigation contributions to streamflow across the western United States

The National Water Model (NWM) provides critical analyses and projections of streamflow that support water management decisions. However, the NWM performs poorly in lower-elevation rivers of the western United States (US). The accuracy of the NWM depends on the fidelity of the model inputs and the representation and calibration of model processes and water sources. To evaluate the NWM performance in the western US, we compared observations of river water isotope ratios ( 18 O / "> 16 O and 2 H / "> 1 H expressed in δ notation) to NWM-flux-estimated (model) river reach isotope ratios. The modeled estimates were calculated from long-term (2000–2019) mean summer (June, July, and August) NWM hydrologic fluxes and gridded isotope ratios using a mass balance approach. The observational dataset comprised 4503 in-stream water isotope observations in 877 reaches across 5 basins. A simple regression between observed and modeled isotope ratios explained 57.9 % ( δ 18 O) and 67.1 % ( δ 2 H) of variance, although observations were 0.5 ‰ ( δ 18 O) and 4.8 ‰ ( δ 2 H) higher, on average, than mass balance estimates. The unexplained variance suggest that the NWM does not include all relevant water fluxes to rivers. To infer possible missing water fluxes, we evaluated patterns in observation–model differences using δ 18 O diff ( δ 18 O obs − δ 18 O mod ) and d diff ( δ 2 H diff - 8 ⋅ δ 18 O diff "> ). We detected evidence of evaporation in observations but not model estimates (negative d diff and positive δ 18 O diff ) at lower-elevation, higher-stream-order, arid sites. The catchment actual-evaporation-to-precipitation ratio, the fraction of streamflow estimated to be derived from agricultural irrigation, and whether a site was reservoir-affected were all significant predictors of d diff in a linear mixed-effects model, with up to 15.2 % of variance explained by fixed effects. This finding is supported by seasonal patterns, groundwater levels, and isotope ratios, and it suggests the importance of including irrigation return flows to rivers, especially in lower-elevation, higher-stream-order, arid rivers of the western US.

Hydrology and Earth Systems Science↗

USGS2023

Groundwater quality in the Mohawk and western New York River Basins, New York, 2016

Water samples were collected from July through December 2016 from 9 production wells and 13 domestic wells in the Mohawk River Basin, and from 17 production wells and 17 domestic wells in the western New York River Basins. The samples were collected and processed by using standard U.S. Geological Survey methods and were analyzed for 320 physicochemical properties and constituents, including dissolved gases, major ions, nutrients, trace elements, pesticides, volatile organic compounds, radionuclides, and indicator bacteria, to characterize groundwater quality in the basins. Analytical results are provided in the companion U.S. Geological Survey data release titled “Groundwater Quality Data From the Mohawk and Western New York River Basins, New York, 2016.” The Mohawk River Basin study area covers 3,500 square miles in New York. Of the 22 wells sampled in the Mohawk River Basin, 8 are completed in sand and gravel, and 14 are completed in bedrock aquifers. Most constituents in the samples from the Mohawk River Basin were present in concentrations below the maximum contaminant levels used in public supply drinking-water regulations by the New York State Department of Health and the U.S. Environmental Protection Agency. Values for some of the properties and concentrations of some constituents—pH, color, iron, manganese, aluminum, sodium, chloride, dissolved solids, radon-222, and heterotrophic plate count—sometimes equaled or exceeded primary, secondary, or proposed drinking-water standards. The western New York River Basins study area covers 5,340 square miles in western New York and includes parts of the Lake Erie and Niagara River Basins, the western Lake Ontario Basin (between the Niagara River and Genesee River Basins), and the Allegheny River Basin. Of the 34 wells sampled in the western New York River Basins, 16 are completed in sand and gravel, and 18 are completed in bedrock aquifers. Most constituents in the samples from the western New York River Basins were present in concentrations below the maximum contaminant levels used in public supply drinking-water regulations by the New York State Department of Health and the U.S. Environmental Protection Agency. Values for some of the properties and concentrations of some constituents—color, chloride, sodium, dissolved solids, iron, manganese, aluminum, arsenic, barium, radon-222, methane, total coliform bacteria, fecal coliform bacteria, and Escherichia coli bacteria—sometimes equaled or exceeded primary, secondary, or proposed drinking-water standards.

New York↗

USGS2021

Methods of data collection and analysis for an assessment of karst aquifer systems between Albany and Buffalo, New York

The U.S. Geological Survey, in cooperation with the New York State Department of Environmental Conservation, catalogued aquifers and closed depressions in a karst-prone area between Albany and Buffalo, New York to provide resource managers information to more efficiently manage and protect groundwater resources. The New York State Department of Environmental Conservation has been working with the agricultural industry to raise awareness of karst aquifer contamination susceptibility and how to reduce effects on surface water and groundwater resources, especially in karst areas. There is also a need to make industries, State and local regulators, planners, and the public aware of New York’s karst resources to properly protect and manage these resources and the quality of surface water and groundwater that flows through the karst aquifer. Publicly available geospatial data were identified, collated, and analyzed for a region of karst terrain extending from Albany to Buffalo. The region was divided into 10 subareas. A series of geospatial datasets were assembled to determine the location and extent of karstic rock; bedrock geology and depth to bedrock; average water-table configuration; surficial geology; soil type, thickness, and hydraulic conductivity; land cover; and closed depressions in the land surface. Repeated glaciation and recession across New York have left the landscape pockmarked with closed depressions, which may or may not be related to the underlying bedrock. Closed depressions in areas where carbonate or evaporite karst are present are of primary concern to this study because of the increased potential of karst aquifer contamination from focused recharge. Closed depressions present in areas not associated with karst bedrock can also be evaluated to better understand their ability to transmit surface water to the groundwater system. Information on closed depressions can be used to develop land-management plans to protect local and regional water resources.

New York↗

USGS2021

Machine learning predicted redox conditions in the glacial aquifer system, northern continental United States

Groundwater supplies 50% of drinking water worldwide and 30% in the United States. Geogenic and anthropogenic contaminants can, however, compromise water quality, thus limiting groundwater availability. Reduction/oxidation (redox) processes and redox conditions affect groundwater quality by influencing the mobility and transport of common geogenic and anthropogenic contaminants. In the glacial aquifer system, northern United States (GLAC, 1.87 million km 2 ), groundwater with high arsenic or manganese concentration is associated with reducing conditions and high nitrate with oxidizing conditions. This study uses machine learning to identify the relative influence of drivers of redox conditions (e.g., residence time vs. reactivity) across the glacial landscape. We developed three‐dimensional boosted regression tree models to predict redox conditions using the likelihood of low dissolved oxygen or high iron as indicators of anoxic conditions. Results indicate that variation in redox condition is controlled primarily by residence time (e.g., groundwater age and relative depth) and to a lesser extent by geochemical reactivity (e.g., subsurface contact time, soil carbon). Older water and deeper wells, along with more water storage or slower water movement was associated with higher probability of anoxic conditions. Mapped model results illustrate regions where anoxic redox conditions may mobilize geogenic contaminants or oxic conditions may limit denitrification potential. Results may also provide simplified redox input for process or predictive models of, for example, arsenic, manganese, or nitrate. Machine learning modeling methods can lead to improved understanding of contaminant occurrence and what drives redox conditions, and the methods may be transferable to other settings.

Northern Continental United States↗

USGS2021

Machine-learning predictions of high arsenic and high manganese at drinking water depths of the glacial aquifer system, northern continental United States

Globally, over 200 million people are chronically exposed to arsenic (As) and/or manganese (Mn) from drinking water. We used machine-learning (ML) boosted regression tree (BRT) models to predict high As (>10 μg/L) and Mn (>300 μg/L) in groundwater from the glacial aquifer system (GLAC), which spans 25 states in the northern United States and provides drinking water to 30 million people. Our BRT models’ predictor variables (PVs) included recently developed three-dimensional estimates of a suite of groundwater age metrics, redox condition, and pH. We also demonstrated a successful approach to significantly improve ML prediction sensitivity for imbalanced data sets (small percentage of high values). We present predictions of the probability of high As and high Mn concentrations in groundwater, and uncertainty, at two nonuniform depth surfaces that represent moving median depths of GLAC domestic and public supply wells within the three-dimensional model domain. Predicted high likelihood of anoxic condition (high iron or low dissolved oxygen), predicted pH, relative well depth, several modeled groundwater age metrics, and hydrologic position were all PVs retained in both models; however, PV importance and influence differed between the models. High-As and high-Mn groundwater was predicted with high likelihood over large portions of the central part of the GLAC.

Environmental Science & Technology↗

USGS2021

Three-dimensional distribution of residence time metrics in the glaciated United States using metamodels trained on general numerical models

Residence time distribution (RTD) is a critically important characteristic of groundwater flow systems; however, it cannot be measured directly. RTD can be inferred from tracer data with analytical models (few parameters) or with numerical models (many parameters). The second approach permits more variation in system properties but is used less frequently than the first because large‐scale numerical models can be resource intensive. Using a novel automated approach, a set of 115 inexpensive general simulation models (GSMs) was used to create RTD metrics (fraction of young groundwater, defined as < 65 years old; mean travel time of young fraction; median travel time of old fraction; and mean path length). GSMs captured the general trends in measured tritium concentrations in 431 wells. Boosted Regression Tree metamodels were trained to predict these RTD metrics using available wall‐to‐wall hydrogeographic digital sets as explanatory features. The metamodels produced a three‐dimensional distribution of predictions throughout the glacial system that generally matched with the numerical model RTD metrics. In addition to the expected importance of aquifer thickness and recharge rate in predicting RTD metrics, two new data sets, Multi‐Order Hydrologic Position (MOHP) and hydrogeologic terrane were important predictors. These variables by themselves produced metamodels with Nash‐Sutcliffe efficiency close to the full metamodel. Metamodel predictions showed that the volume of young groundwater stored in the glaciated U.S. is about 6,000 km 3 , or about 0.5% of globally stored young groundwater.

Water Resources Research↗

USGS2020

Machine learning predictions of pH in the Glacial Aquifer System, Northern USA

A boosted regression tree model was developed to predict pH conditions in three dimensions throughout the glacial aquifer system of the contiguous United States using pH measurements in samples from 18,386 wells and predictor variables that represent aspects of the hydrogeologic setting. Model results indicate that the carbonate content of soils and aquifer materials strongly controls pH and, when coupled with long flowpaths, results in the most alkaline conditions. Conversely, in areas where glacial sediments are thin and carbonate‐poor, pH conditions remain acidic. At depths typical of drinking‐water supplies, predicted pH >7.5—which is associated with arsenic mobilization—occurs more frequently than predicted pH <6—which is associated with water corrosivity and the mobilization of other trace elements. A novel aspect of this model was the inclusion of numerically based estimates of groundwater flow characteristics (age and flowpath length) as predictor variables. The sensitivity of pH predictions to these variables was consistent with hydrologic understanding of groundwater flow systems and the geochemical evolution of groundwater quality. The model was not developed to provide precise estimates of pH at any given location. Rather, it can be used to more generally identify areas where contaminants may be mobilized into groundwater and where corrosivity issues may be of concern to prioritize areas for future groundwater monitoring.

Groundwater↗

USGS2020

Statewide assessment of karst aquifers in New York with an inventory of closed-depression and focused-recharge features

Karst is a landscape formed from the dissolution of soluble rock or rock containing minerals that are easily dissolved from within the rock. The landscape is characterized by sinkholes, caves, losing streams, springs, and underground drainage systems, which rapidly move water through the karst. The two forms of karst in New York State include carbonate karst, which forms in carbonate rock (limestone, marble, and dolostone), and evaporite karst, which forms in rock that contains the evaporite minerals gypsum and halite. Past and recent studies of karst across the State have shown that areas of focused recharge in karstic carbonate rock allow contaminants to enter aquifer systems with little attenuation. Focused areas of recharge need to be identified to help prevent such contamination from sources on or adjacent to the karst. The New York State Departments of Environmental Conservation and Health are collaborating with the agricultural community to make farmers and farm-planning advisors more aware of karst and how to manage daily farming activities to reduce their impact on surface water and groundwater resources, especially in karst areas. There is also a need to make regulators, planners, and the general public aware of New York’s karst resources and to properly protect and manage these resources to protect the quality of groundwater and surface water that can flow into, through, and from karst bedrock. Using publicly available geospatial data, karst bedrock and closed depressions over or near karst rock were identified across New York. Carbonate, evaporite, and marble geologic units were selected from a statewide 1:250,000-scale bedrock geology dataset. The selected geologic units were intersected with 7.5-minute quadrangle maps to define the study area. The U.S. Geological Survey has compiled an inventory of closed depressions from statewide digital contour data, scanned 7.5-minute topographic maps known as a digital raster graphics, and light detection and ranging (lidar) digital elevation models. Analysis of the data resulted in the identification of 5,023 closed depressions statewide. The inventory was conducted to eliminate duplication of results from analysis of the three data sources. A series of overlay analyses was conducted using the closed depressions and thematic data known to be key factors in determining the probability of a closed depression contributing to focused groundwater recharge; the thematic data include bedrock geology, soil type, soil infiltration rate, and land cover. Though the extent of karst development is important in understanding the interaction between surface water and groundwater in karst terrains, some of the worst cases of groundwater contamination in karst can occur where only minor karst features might be present. The presence of karst—be it a short section of a solutioned fracture or an extensive cave system—requires careful consideration, forward-looking environmental planning, and consistent water-quality protection to preserve New York State’s water resources.

New York↗

USGS2019

Groundwater quality in the Delaware, Genesee, and St. Lawrence River Basins, New York, 2015

The U.S. Geological Survey, in cooperation with the New York State Department of Environmental Conservation, collected groundwater samples from 5 production wells and 5 domestic wells in the Delaware River Basin, 8 production wells and 7 domestic wells in the Genesee River Basin, and 1 municipal well, 7 production wells, and 13 domestic wells in the St. Lawrence River Basin in New York. All samples were collected from May through November 2015 in an effort to characterize groundwater quality in these basins. The samples were collected and processed by using standard U.S. Geological Survey procedures and were analyzed for 148 physiochemical properties and constituents, including dissolved gases, major ions, nutrients, trace elements, pesticides, volatile organic compounds, radionuclides, and indicator bacteria. The Delaware River Basin study area covers 2,360 square miles (mi 2 ) in southeastern New York. Of the 10 wells sampled in the Delaware River Basin, 3 are completed in sand and gravel, and 7 are completed in bedrock. Groundwater in the Delaware River Basin was generally of good quality, although properties and concentrations of some constituents—pH, iron, manganese, aluminum, radon-222, and total coliform bacteria—sometimes equaled or exceeded primary, secondary, or proposed drinking-water standards. The constituent most frequently detected in concentrations exceeding drinking-water standards (10 of 10 samples) was radon-222. The Genesee River Basin study area includes the entire 2,439 mi 2 of the basin in western New York. Of the 15 wells sampled in the Genesee River Basin, 6 are completed in sand and gravel, and 9 are completed in bedrock. Groundwater in the Genesee River Basin was generally of good quality, although properties and concentrations of some constituents—chloride, sodium, dissolved solids, iron, manganese, aluminum, arsenic, radon-222, methane, total coliform bacteria, fecal coliform bacteria, and Escherichia coli bacteria—sometimes equaled or exceeded primary, secondary, or proposed drinking-water standards. The constituent most frequently detected in concentrations exceeding drinking-water standards (12 of 15 samples) was radon-222. The St. Lawrence River Basin study area includes the entire 5,650 mi 2 of the basin in northeastern New York. Of the 21 wells sampled in the St. Lawrence River Basin, 7 are completed in sand and gravel, and 14 are completed in bedrock. Groundwater in the St. Lawrence River Basin was generally of good quality, although properties and concentrations of some constituents—pH, chloride, sodium, dissolved solids, iron, manganese, sulfate, nitrate, radon-222, total coliform bacteria, fecal coliform bacteria, and Escherichia coli bacteria—sometimes equaled or exceeded primary, secondary, or proposed drinking-water standards. The constituent most frequently detected in concentrations exceeding drinking-water standards (14 of 21 samples) was radon-222.

New York↗

USGS2018

Hydrogeologic framework for characterization and occurrence of confined and unconfined aquifers in quaternary sediments in the glaciated conterminous United States—A digital map compilation and database

The U.S. Geological Survey has created a hydrogeologic framework for Quaternary sediments in glaciated areas of the conterminous United States that categorizes, maps, and characterizes the glacial sediments at and beneath the land surface. The hydrogeologic framework divides the glaciated United States into 17 distinct hydrogeologic terranes using a geologic approach based on previous mapping, and was characterized using the Glacial Environments and Surficial Sediments geodatabase compiled from the Quaternary Atlas of the United States map series, the Surficial Materials Map of the United States, and several Integrated Geologic Map Databases for the United States; a groundwater use database compiled from public-supply, water-well data; and a lithologic database compiled from State-managed well records and geologic logs. This framework is to be used to assess the occurrence and characteristics of confined and unconfined glacial aquifers, their distribution and extent, and their potential intrinsic susceptibility and vulnerability.

Data Series↗

USGS2018

Characterization and occurrence of confined and unconfined aquifers in Quaternary sediments in the glaciated conterminous United States

The glacial aquifer system, which is a collection of aquifers within Quaternary sediments in the glaciated conterminous United States, is a principal aquifer that supplies groundwater that serves about 42 million people and accounts for about 5 percent of the Nation’s drinking water. This aquifer system (the area of maximum glacial advance) underlies parts of 25 States and covers 1.87×10 6 square kilometers. A hydrogeologic framework is presented that divides the glaciated United States into 17 distinct hydrogeologic terranes using a geologic approach based on previous mapping. Each hydrogeologic terrane contains Quaternary sediment that is derived from a common depositional history and can be characterized by similar texture and thickness. Characteristics of Quaternary sediments are described using attributes computed from a lithologic database of well logs compiled from 24 States (excluding Kentucky). The hydrogeologic framework presents a nationwide picture of the glacial aquifer system and provides generalizations concerning the nature of aquifers within it (for example, whether the aquifers are shallow or deep, and unconfined or confined). In this way insights can be gained from understanding the similarities and differences in distinct parts of the glacial aquifer system and how they relate to water use and quality and to aquifer vulnerability. Delineation of hydrogeologic terranes was based on an interpretation of existing geologic mapping of Quaternary sediments and the thickness of unconsolidated material. Overall thickness of Quaternary sediment was used to qualitatively rank the generalized complexity of the hydrogeologic framework in each terrane: “lower” complexity (assigned a terrane code 1), “moderate” complexity (terrane code 2), and “higher” complexity (terrane code 3). Letter designations appended to the terrane codes (for example, 1A, 1B, or 1C) differentiate terranes of similar complexity. Two unique areas, where thick, stratified, coarse-grained sediment dominates, were assigned terrane code 4. Elements of this hydrogeologic framework include a glacial environments and surficial sediments geodatabase, which includes lithologic, geomorphic, and stratigraphic characterization of Quaternary sediments based on previous mapping; a gridded database of sediment and aquifer characteristics computed from lithologic logs obtained from water-well driller records; a water-use database with information on public-water supply systems and sources of groundwater; and estimated recharge computed from a geologically based soil-water balance model. A generalized map of the bedrock geology based on previous State-level mapping is included as well. Quaternary sediment in the glaciated United States includes glacial, postglacial (Holocene) and nonglacial sediments. At land surface, 60 percent of the glacial sediment is till. Large areas of outwash and ice contact sediments are extensive throughout the Midwest but generally are confined to valleys in the Northeast and the Northwest. Lacustrine sediments were deposited in proglacial lakes adjacent to the present Great Lakes and in glacial Lake Agassiz in the eastern Dakotas and northwestern Minnesota. The median thickness of Quaternary sediment ranges from 6 to 45 meters across the 17 hydrogeologic terranes, but the maximum thickness is more than 500 meters in some areas. Quaternary sediments generally contain less than 10 percent coarse material; the median range is near zero percent under till to about 50 percent under ice contact and outwash sediments. About 80 percent of the coarse material lies within 25 to 40 meters of land surface. In most of the glaciated United States, there is a small likelihood of penetrating an aquifer-material interval containing coarse material at least 3 meters thick. A single aquifer-material interval was recorded in about 44 percent of lithologic logs, whereas about 11 percent of the logs penetrated multiple intervals. About 44 percent of water wells in the lithologic database are completed in Quaternary sediment, and many of these Quaternary water wells (42 percent) are confined by at least 7.5 meters of fine materials. About 33 percent of these Quaternary water wells are unconfined—the remainder are where only thin layers (less than 3 meters) of coarse material are present. The median depths of Quaternary water wells range from 13 to 40 meters among the 17 hydrogeologic terranes. Recharge ranges from more than 400 millimeters per year in the Northeast to 11 millimeters or less per year in the Dakotas and Montana (median value of 136 millimeters per year). Annual groundwater withdrawals compiled by county range on an areal basis from less than 1 to 370 millimeters per year, and the mean is 7.4 millimeters per year. About 36 percent of the withdrawals are for public-water supply, of which 70 percent are derived from Quaternary sediments. Groundwater withdrawals are less than 10 percent of recharge throughout most of the glaciated conterminous United States but are a larger proportion of recharge near urban areas in the Northeast and the Midwest, and in counties throughout drier parts of the Midwest. The salient characteristics of the 17 hydrogeologic terranes are presented through maps and a set of descriptive plots to facilitate visual comparisons between selected sediment and aquifer characteristics. The thickness of Quaternary sediment generally increases from the lower complexity terranes through the higher complexity terranes, consistent with their delineation. Median proportions of coarse material in Quaternary sediment and depths to aquifer-material intervals are highly variable (less than 10 to 50 percent, and 0 to 30 meters, respectively). Median thicknesses of aquifer-material intervals generally fall within a narrow range (10 to 20 meters), except in two terranes that contain thick coarse-grained sediment (30 to 35 meters). The source of water in wells varies from mostly bedrock wells in the lower complexity terranes to mostly Quaternary wells in the higher complexity terranes where the sediment is thickest. A tree diagram compiled from a hierarchical cluster analysis of a matrix composed of metrics based on sediment and aquifer characteristics, and the distribution of water wells in each terrane, indicates some groups of terranes that can be treated as comparable when analyzing groundwater flow and quality. Aquifer-material intervals indicated on maps prepared from the lithologic logs, including unconfined and confined conditions, correlate well with aquifer systems delineated on state maps for Illinois, Indiana, and North Dakota. The large scale of the study limits the resolution at which the maps can be interpreted, however, and alluvial units are not mapped correctly for some valleys in the Northeast and the Northwest. Lithologic logs used in the study are biased toward shallow depths because not all logs penetrate the entire thickness of Quaternary sediment, but this bias should not limit the utility of the sediment and aquifer descriptions because shallow depths are commonly exploited for water supply. The hydrogeologic framework will support ongoing studies of groundwater flow and quality in the U.S. Geological Survey National Water Quality Assessment program for the glaciated United States.

Scientific Investigations Report↗

USGS2018

Elevated manganese concentrations in United States groundwater, role of land surface–soil–aquifer connections

Chemical data from 43 334 wells were used to examine the role of land surface–soil–aquifer connections in producing elevated manganese concentrations (>300 μg/L) in United States (U.S.) groundwater. Elevated concentrations of manganese and dissolved organic carbon (DOC) in groundwater are associated with shallow, anoxic water tables and soils enriched in organic carbon, suggesting soil-derived DOC supports manganese reduction and mobilization in shallow groundwater. Manganese and DOC concentrations are higher near rivers than farther from rivers, suggesting river-derived DOC also supports manganese mobilization. Anthropogenic nitrogen may also affect manganese concentrations in groundwater. In parts of the northeastern U.S. containing poorly buffered soils, ∼40% of the samples with elevated manganese concentrations have pH values < 6 and elevated concentrations of nitrate relative to samples with pH ≥ 6, suggesting acidic recharge produced by the oxidation of ammonium in fertilizer helps mobilize manganese. An estimated 2.6 million people potentially consume groundwater with elevated manganese concentrations, the highest densities of which occur near rivers and in areas with organic carbon rich soil. Results from this study indicate land surface–soil–aquifer connections play an important role in producing elevated manganese concentrations in groundwater used for human consumption.

Environmental Science & Technology↗

USGS2018

Metamodeling and mapping of nitrate flux in the unsaturated zone and groundwater, Wisconsin, USA

Nitrate contamination of groundwater in agricultural areas poses a major challenge to the sustainability of water resources. Aquifer vulnerability models are useful tools that can help resource managers identify areas of concern, but quantifying nitrogen (N) inputs in such models is challenging, especially at large spatial scales. We sought to improve regional nitrate (NO 3 − ) input functions by characterizing unsaturated zone NO 3 − transport to groundwater through use of surrogate, machine-learning metamodels of a process-based N flux model. The metamodels used boosted regression trees (BRTs) to relate mappable landscape variables to parameters and outputs of a previous “vertical flux method” (VFM) applied at sampled wells in the Fox, Wolf, and Peshtigo (FWP) river basins in northeastern Wisconsin. In this context, the metamodels upscaled the VFM results throughout the region, and the VFM parameters and outputs are the metamodel response variables. The study area encompassed the domain of a detailed numerical model that provided additional predictor variables, including groundwater recharge, to the metamodels. We used a statistical learning framework to test a range of model complexities to identify suitable hyperparameters of the six BRT metamodels corresponding to each response variable of interest: NO 3 − source concentration factor (which determines the local NO 3 − input concentration); unsaturated zone travel time; NO 3 − concentration at the water table in 1980, 2000, and 2020 (three separate metamodels); and NO 3 − “extinction depth”, the eventual steady state depth of the NO 3 − front. The final metamodels were trained to 129 wells within the active numerical flow model area, and considered 58 mappable predictor variables compiled in a geographic information system (GIS). These metamodels had training and cross-validation testing R 2 values of 0.52 – 0.86 and 0.22 – 0.38, respectively, and predictions were compiled as maps of the above response variables. Testing performance was reasonable, considering that we limited the metamodel predictor variables to mappable factors as opposed to using all available VFM input variables. Relationships between metamodel predictor variables and mapped outputs were generally consistent with expectations, e.g. with greater source concentrations and NO 3 − at the groundwater table in areas of intensive crop use and well drained soils. Shorter unsaturated zone travel times in poorly drained areas likely indicated preferential flow through clay soils, and a tendency for fine grained deposits to collocate with areas of shallower water table. Numerical estimates of groundwater recharge were important in the metamodels and may have been a proxy for N input and redox conditions in the northern FWP, which had shallow predicted NO 3 − extinction depth. The metamodel results provide proof-of-concept for regional characterization of unsaturated zone NO 3 − transport processes in a statistical framework based on readily mappable GIS input variables.

Wisconsin↗

USGS2016

Groundwater quality in the Lake Champlain and Susquehanna River basins, New York, 2014

In a study conducted by the U.S. Geological Survey in cooperation with the New York State Department of Environmental Conservation, groundwater samples were collected from 6 production wells and 7 domestic wells in the Lake Champlain Basin and from 11 production wells and 9 domestic wells in the Susquehanna River Basin in New York. All samples were collected from June through December 2014 to characterize groundwater quality in these basins. The samples were collected and processed using standard procedures of the U.S. Geological Survey and were analyzed for 148 physiochemical properties and constituents, including dissolved gases, major ions, nutrients, trace elements, pesticides, volatile organic compounds, radionuclides, and indicator bacteria. The Lake Champlain Basin study area covers the 3,050 square miles of the basin in northeastern New York; the remaining part of the basin is in Vermont and Canada. Of the 13 wells sampled in the Lake Champlain Basin, 6 are completed in sand and gravel, and 7 are completed in bedrock. Groundwater in the Lake Champlain Basin was generally of good quality, although properties and concentrations of some constituents— fluoride, iron, manganese, dissolved solids, sodium, radon-222, total coliform bacteria, fecal coliform bacteria, and Escherichia coli bacteria—sometimes equaled or exceeded primary, secondary, or proposed drinking-water standards. The constituent most frequently detected in concentrations exceeding drinking-water standards (5 of 13 samples) was radon-222. The Susquehanna River Basin study area covers the entire 4,522 square miles of the basin in south-central New York; the remaining part of the basin is in Pennsylvania. Of the 20 wells sampled in the Susquehanna River Basin, 11 are completed in sand and gravel, and 9 are completed in bedrock. Groundwater in the Susquehanna River Basin was generally of good quality, although properties and concentrations of some constituents—pH, chloride, sodium, dissolved solids, iron, manganese, aluminum, arsenic, barium, gross-alpha radioactivity, radon-222, methane, total coliform bacteria, and fecal coliform bacteria—sometimes equaled or exceeded primary, secondary, or proposed drinking-water standards. As in the Lake Champlain Basin, the constituent most frequently detected in concentrations exceeding drinking-water standards (13 of 20 samples) was radon-222.

New York↗

USGS2016

Streamflow and estimated loads of phosphorus and dissolved and suspended solids from selected tributaries to Lake Ontario, New York, water years 2012–14

This report presents results of the evaluation and interpretation of hydrologic and water-quality data collected as part of a cooperative program between the U.S. Geological Survey and the U.S. Environmental Protection Agency. Streamflow, phosphorus, and solids dissolved and suspended in stream water were the focus of monitoring by the U.S. Geological Survey at 10 sites on 9 selected tributaries to Lake Ontario during the period from October 2011 through September 2014. Streamflow yields (flow per unit area) were the highest from the Salmon River Basin due to sustained yields from the Tug Hill aquifer. The Eighteenmile Creek streamflow yields also were high as a result of sustained base flow contributions from a dam just upstream of the U.S. Geological Survey monitoring station at Burt. The lowest streamflow yields were measured in the Honeoye Creek Basin, which reflects a decrease in flow because of withdrawals from Canadice and Hemlock Lakes for the water supply of the City of Rochester. The Eighteenmile Creek and Oak Orchard Creek Basins had relatively high yields due in part to groundwater contributions from the Niagara Escarpment and seasonal releases from the New York State Barge Canal. Annual constituent yields (load per unit area) of suspended solids, phosphorus, orthophosphate, and dissolved solids were computed to assess the relative contributions and allow direct comparison of loads among the monitored basins. High yields of total suspended solids were attributed to agricultural land use in highly erodible soils at all sites. The Genesee River, Irondequoit Creek, and Honeoye Creek had the highest concentrations and largest mean yields of total suspended solids (165 short tons per square mile [t/mi 2 ], 184 t/mi 2 , and 89.7 t/mi 2 , respectively) of the study sites. Samples from Eighteenmile Creek, Oak Orchard Creek at Kenyonville, and Irondequoit Creek had the highest concentrations and largest mean yields of phosphorus (0.27 t/mi 2 , 0.26 t/mi 2 , and 0.20 t/mi 2 , respectively) and orthophosphate (0.17 t/mi 2 , 0.13 t/mi 2 , and 0.04 t/mi 2 , respectively) of the study sites. These results were attributed to a combination of sources, including discharges from wastewater treatment plants, diversions from the New York State Barge Canal, and manure and fertilizers applied to agricultural land. Yields of phosphorus also were high in the Genesee River Basin (0.17 t/mi 2 ) and were presumably associated with nutrient and sediment transport from agricultural land and from streambank erosion. The Salmon and Black Rivers, which drain a substantial amount of forested land and are influenced by large groundwater discharges, had the lowest concentrations and yields of phosphorus and orthophosphate of the study sites. Mean annual yields of dissolved solids were the highest in Irondequoit Creek due to a high percentage of urbanized area in the basin and in Oak Orchard Creek at Kenyonville and in Eighteenmile Creek due to groundwater contributions from the Niagara Escarpment. High yields of dissolved solids of 840 t/mi 2 , 829 t/mi 2 , and 715 t/mi 2 , respectively, from these basins can be attributed to seasonal chloride yields associated with use of road deicing salts. The Niagara Escarpment can produce large amounts of dissolved solids from the dissolution of minerals (a continual process reflected in base flow samples). Groundwater inflows in the Salmon River have very low concentrations of dissolved solids due to minimal bedrock interaction along the Tug Hill Plateau and discharge from the Tug Hill sand and gravel aquifer, which has minimal mineralization.

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USGS2015

Groundwater quality in the Chemung River, Eastern Lake Ontario, and Lower Hudson River Basins, New York, 2013

In a study conducted by the U.S. Geological Survey (USGS) in cooperation with the New York State Department of Environmental Conservation, water samples were collected from 4 production wells and 4 domestic wells in the Chemung River Basin, 8 production wells and 7 domestic wells in the Eastern Lake Ontario Basin, and 12 production wells and 13 domestic wells in the Lower Hudson River Basin (south of the Federal Lock and Dam at Troy) in New York. All samples were collected in June, July, and August 2013 to characterize groundwater quality in these basins. The samples were collected and processed using standard USGS procedures and were analyzed for 148 physiochemical properties and constituents, including dissolved gases, major ions, nutrients, trace elements, pesticides, volatile organic compounds, radionuclides, and indicator bacteria. The Chemung River Basin study area covers 1,744 square miles in south-central New York and encompasses the part of the Chemung River Basin that lies within New York. Two of the wells sampled in the Chemung River Basin are completed in sand and gravel, and 6 are completed in bedrock. Groundwater in the Chemung River Basin was generally of good quality, although properties and concentrations of some constituents—sodium, arsenic, aluminum, iron, manganese, radon-222, total coliform bacteria, and Escherichia coli bacteria—equaled or exceeded primary, secondary, or proposed drinking-water standards. The constituent most frequently detected in concentrations exceeding drinking-water standards (six of eight samples) was radon-222. The Eastern Lake Ontario Basin study area covers 3,225 square miles in north-central New York. The Eastern Lake Ontario Basin (between the Oswego River Basin and the St. Lawrence River Basin) includes the Mid-Northern Lake Ontario Basin, the Black River Basin, and the Chaumont River-Perch River Basin. Five of the wells sampled in the Eastern Lake Ontario Basin are completed in sand and gravel, and 10 are completed in bedrock. Groundwater in the Eastern Lake Ontario Basin was generally of good quality, although properties and concentrations of some constituents—color, pH, sodium, dissolved solids, fluoride, iron, manganese, uranium, gross-α radioactivity, radon-222, total coliform bacteria, and fecal coliform bacteria—equaled or exceeded primary, secondary, or proposed drinking-water standards. The constituent most frequently detected in concentrations exceeding drinking-water standards (10 of 15 samples) was radon-222. The Lower Hudson River Basin study area covers 5,607 square miles and encompasses the part of the Lower Hudson River Basin that lies within New York plus the parts of the Housatonic, Hackensack, Bronx, and Saugatuck River Basins that are in New York. Twelve of the wells sampled in the Lower Hudson River Basin are completed in sand-and-gravel deposits, and 13 are completed in bedrock. Groundwater in the Lower Hudson River Basin was generally of good quality, although properties and concentrations of some constituents—pH, sodium, chloride, dissolved solids, arsenic, aluminum, iron, manganese, radon-222, total coliform bacteria, fecal coliform bacteria, Escherichia coli bacteria, and heterotrophic plate count—equaled or exceeded primary, secondary, or proposed drinking-water standards. The constituent most frequently detected in concentrations exceeding drinking-water standards (20 of 25 samples) was radon-222.

New York↗

USGS2014

Groundwater quality in central New York, 2012

Water samples were collected from 14 production wells and 15 private wells in central New York from August through December 2012 in a study conducted by the U.S. Geological Survey in cooperation with the New York State Department of Environmental Conservation. The samples were analyzed to characterize the groundwater quality in unconsolidated and bedrock aquifers in this area. Fifteen of the wells are finished in sand-and-gravel aquifers, and 14 are finished in bedrock aquifers. Six of the 29 wells were sampled in a previous central New York study, which was conducted in 2007. Water samples from the 2012 study were analyzed for 147 physiochemical properties and constituents, including major ions, nutrients, trace elements, radionuclides, pesticides, volatile organic compounds, dissolved gases (argon, carbon dioxide, methane, nitrogen, oxygen), and indicator bacteria. Results of the water-quality analyses are presented in tabular form for individual wells, and summary statistics for specific constituents are presented by aquifer type. The results are compared with Federal and New York State drinking-water standards, which typically are identical. The results indicate that the groundwater generally is of acceptable quality, although for all of the wells sampled, at least one of the following constituents was detected at a concentration that exceeded current or proposed Federal or New York State drinking-water standards: color (2 samples), pH (7 samples), sodium (9 samples), chloride (2 samples), fluoride (2 samples), sulfate (2 samples), dissolved solids (8 samples), aluminum (4 samples), arsenic (1 sample), iron (9 samples), manganese (13 samples), radon-222 (13 samples), total coliform bacteria (6 samples), and heterotrophic bacteria (2 samples). Drinking-water standards for nitrate, nitrite, antimony, barium, beryllium, cadmium, chromium, copper, lead, mercury, selenium, silver, thallium, zinc, gross alpha radioactivity, uranium, fecal coliform, and Escherichia coli were not exceeded in any of the samples collected. None of the pesticides or volatile organic compounds analyzed exceeded drinking-water standards. Methane was detected in 11 sand-and-gravel wells and 9 bedrock wells. Five of the 14 bedrock wells had water with methane concentrations approaching 10 mg/L; water in one bedrock well had 37 mg/L of methane.

New York↗