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USGS2026

As above, so below? A framework for integrating long-term water quantity trends reveals divergent patterns in groundwater and low streamflow across the United States

Climate, land-use, and disturbance drive long-term global trends in groundwater levels and streamflow. At large scales, these trends are typically considered separately, despite the well-established concept that groundwater and surface water comprise a single resource. Joint trend assessment at national scales is challenging because it requires pairing and aggregating data from spatially disparate streamflow and groundwater monitoring sites for which no established framework exists. Here, we evaluate alternative approaches for integrating groundwater and streamflow data to enable joint trend analysis—a critical step toward understanding how water-budget components respond concurrently and interactively to environmental drivers. Mann–Kendall trends were computed for individual groundwater (annual mean depth) and streamflow (annual low of 7 d averages) sites across the U.S over 21- (2000–2020), 31- (1990–2020), and 41-year (1980–2020) periods. Regional Kendall trends were calculated using five spatially contiguous and noncontiguous regional classifications for aggregation based on subsurface (e.g. aquifer, geology) and surface (e.g. watershed, landscape) characteristics. Site-level results revealed contrasting trends, with tendencies toward increasing low flows (wetting) and increasing groundwater depths (drying). Agreement between streamflow and groundwater trends increased with regional aggregation and longer timeframes, though persistent skew toward streamflow wetting and groundwater drying remained. Results varied by region and trend period, with notable consistencies: unified drying in the West/Southwest and wetting in the Upper Midwest. Directional mismatches in long-term trends were prominent in the High Plains and Mississippi Alluvial Plain, whereas near-term mismatches were most evident in the Northwest. Aggregation by hydrologic landscape regions (HLR) yielded the greatest agreement between groundwater and streamflow trends. These findings indicate that coupled responses may represent combined influences of climate, relief, and geology, as captured by HLR, more strongly than geography or geology alone. Integrated water availability assessments may benefit from a multi-characteristic classification framework to treat groundwater and surface water as a unified resource.

Environmental Research: Water↗

USGS2007

Geochemical data from produced water contamination investigations: Osage-Skiatook Petroleum Environmental Research (OSPER) sites, Osage County, Oklahoma

We report chemical and isotopic analyses of 345 water samples collected from the Osage-Skiatook Petroleum Environmental Research (OSPER) project. Water samples were collected as part of an ongoing multi-year USGS investigation to study the transport, fate, natural attenuation, and ecosystem impacts of inorganic salts and organic compounds present in produced water releases at two oil and gas production sites from an aging petroleum field located in Osage County, in northeast Oklahoma. The water samples were collected primarily from monitoring wells and surface waters at the two research sites, OSPER A (legacy site) and OSPER B (active site), during the period March, 2001 to February, 2005. The data include produced water samples taken from seven active oil wells, one coal-bed methane well and two domestic groundwater wells in the vicinity of the OSPER sites.

Oklahoma↗

USGS1987

Water-quality data-collection activities in Colorado and Ohio; Phase II, Evaluation of 1984 field and laboratory quality-assurance practices

Serious questions have been raised by Congress about the usefulness of water-quality data for addressing issues of regional and national scope and, especially, for characterizing the current quality of the Nation's streams and ground water. In response, the U.S. Geological Survey has undertaken a pilot study in Colorado and Ohio to (1) determine the characteristics of current (1984) water-quality data-collection activities of Federal, regional, State, and local agencies, and academic institutions; and (2) determine how well the data from these activities, collected for various purposes and using different procedures, can be used to improve our ability to answer major broad-scope questions, such as: A. What are (or were) natural or near-natural water-quality conditions? B. What are existing water-quality conditions? C. How has water quality changed, and how do the changes relate to human activities? Colorado and Ohio were chosen for the pilot study largely because they represent regions with different types of waterquality concerns and programs. The study has been divided into three phases, the objectives of which are: Phase I--Inventory water-quality data-collection programs, including costs, and identify those programs that met a set of broad criteria for producing data that are potentially appropriate for water-quality assessments of regional and national scope. Phase II--Evaluate the quality assurance of field and laboratory procedures used in producing the data from programs that met the broad criteria of Phase I. Phase III--Compile the qualifying data and evaluate the adequacy of this data base for addressing selected water-quality questions of regional and national scope. Water-quality data are collected by a large number of organizations for diverse purposes ranging from meeting statutory requirements to research on water chemistry. Combining these individual data bases is an appealing and potentially cost-effective way to attempt to develop a data base adequate for regional or national water-quality assessments. However, to combine data from diverse sources, field and laboratory procedures used to produce the data need to be equivalent and need to meet specific qualityassurance standards. It is these factors that are the focus of Phase II, which is described in this report. In the first phase of this study, an inventory was made of all public organizations and academic institutions that undertook water-quality data-collection activities in Colorado and Ohio in 1984. Water-quality programs identified in Phase I were tested against a set of broad screening criteria. A total of 44 waterquality programs in Colorado and 29 programs in Ohio passed the Phase-I screen and were examined in Phase II. These programs accounted for an estimated 165,000 analyses in Colorado and 76,300 analyses in Ohio for 20 selected constituents and properties. Although qualifying programs included both surface- and ground-water sampling, they emphasized surface waters and produced few groundwater analyses (3,660 for Colorado and 470 for Ohio). For Phase II, information about field and laboratory qualityassurance practices was provided by each organization and its supporting laboratories through questionnaires. This information was evaluated against a set of specific criteria for field and laboratory practices. The criteria were developed from guidelines published by public agencies and professional organizations such as the American Public Health Association, the U.Sc, Environmental Protection Agency, and the U.S. Geological Survey. Each of the eight criteria that comprise the Phase-II screen fall into one of two major categories--field practices or laboratory practices.

Colorado, Ohio↗

USGS2026

The global proliferation of aquatic, benthic Microcoleus : Taxonomy, distribution, toxin production, ecology, and future directions

There have been sporadic reports of aquatic, benthic Microcoleus proliferations in freshwater rivers, lakes, and reservoirs for four decades, with reports increasing in frequency over the last twenty years, suggesting a possible rise in their global distribution, frequency, and intensity. Microcoleus can produce anatoxins which are neurotoxic, and ingestion of toxic mats has caused hundreds of dog fatalities and raised serious human and ecological health concerns. This review synthesizes and evaluates current knowledge on Microcoleus distribution, taxonomy, toxin production, toxicity, ecology, environmental drivers, and biotic interactions. Toxin-producing Microcoleus have been reported in at least 18 countries, though many regions have not conducted toxin testing, suggesting a broader but under-reported distribution. Proliferations occur across diverse habitats, including cobble-bedded streams, large sandy rivers, reservoirs, and lakes. Microcoleus proliferations also occur on macrophytes, both in lakes and rivers. Genomic analyses currently classify anatoxin-producing Microcoleus into distinct species, with all known anatoxin-producers isolated from freshwater ecosystems. Anatoxin concentrations vary widely over space and time, within and among waterbodies. While studies on environmental drivers remain limited, research in cobble-bedded rivers suggests that moderate enrichment of dissolved inorganic nitrogen and low dissolved reactive phosphorus concentrations in the water column promote proliferation. Metagenomic approaches have revealed unique nutrient acquisition and storage strategies used by Microcoleus . Key knowledge gaps remain around the environmental and ecological triggers of proliferation, toxin production, genomic diversity and microbial interactions. Addressing these gaps through coordinated, global studies using robust datasets and consistent methods is critical to improve prediction, monitoring, and mitigation of this increasingly widespread public and ecological health threat.

Water Research↗

USGS2011

Water storage at the Panola Mountain Research Watershed, Georgia, USA

Storage is a major component of a catchment water balance particularly when the water balance components are evaluated on short time scales, that is, less than annual. We propose a method of determining the storage-discharge relation using an exponential function and daily precipitation, potential evapotranspiration (PET) and baseflow during the dormant season when evapotranspiration (ET) is low. The method was applied to the 22-year data series of the 0.41-ha forested Panola Mountain Research Watershed, Georgia. The relation of cumulative daily precipitation minus daily runoff and PET versus baseflow was highly significant (r2=0.92, p<0.0001), but the initial storage for each year varied markedly. For the 22-year study period, annual precipitation and runoff averaged 1240 and 380mm, respectively, whereas the absolute catchment storage range was ~400mm, averaging 219mm annually, which is attributed to contributions of soil water and groundwater. The soil moisture of a catchment average 1-m soil depth was evaluated and suggests that there was an active (changes in soil storage during stormflow) and passive (a longer-term seasonal cycle) soil water storage with ranges of 40-70 and 100-120mm, respectively. The active soil water storage was short term on the order of days during and immediately after rainstorms, and the passive or seasonal soil storage was highest during winter when ET was lowest and lowest during summer when ET was highest. An estimate of ET from daily changes in soil moisture (ETSM) during recessions was comparable with PET during the dormant season (1.5mmday-1) but was much lower during the growing season (June through August); monthly average SMET and PET ranged from 2.8 to 4.0mmday-1 and from 4.5 to 5.5mmday-1, respectively. The growing season difference is attributed to the overestimation of PET. ETSM estimates were comparable with those derived from hillslope water balances during sprinkling experiments. Master recession curves derived from the storage-discharge relation adjusted seasonally for ET (1.5 and 4.0mmday-1 during the dormant and growing seasons, respectively) fit actual recessions extremely well. ?? 2011 John Wiley & Sons, Ltd.

Hydrological Processes↗

USGS2001

U.S. Geological Survey Activities Related to American Indians and Alaska Natives Fiscal Year 2001

Information is a resource that can help Native American governments and their people. The U.S. Geological Survey (USGS) makes available technical expertise, reports, and other impartial information sources that can benefit Native Americans interested in subsistence issues, water, land use, and the health of many parts of the environment. The USGS works in cooperation with American Indian and Alaska Native governments, conducting research on water and mineral resources, animals and plants of environmental, economic, or subsistence importance, natural hazards, and geologic resources. Digital data on cartography, mineral resources, stream flow, biota, and other topics are available to American Indian and Alaska Native individuals and institutions. The USGS recognizes the need to learn from and share knowledge with Native peoples. This report describes most of the activities that the USGS conducted with American Indian and Alaska Native governments, educational institutions, and individuals during Federal fiscal year 2001. Some of these USGS activities were carried out in concert with the Bureau of Indian Affairs (BIA). Others were conducted by Tribes and the USGS. In 2001, the USGS began examining its activities related to American Indians and Alaska Natives to determine how it can better serve these customers within its mandates. A growing number of Tribal governments, educational institutions, and other Tribal organizations have begun using geographic information systems and other digital technologies in recent years. As Tribes become more interested in and more adept at managing digital information, they are seeking relevant data from the USGS more frequently. Using digital technologies provides Tribal governments with additional means of managing lands and resources for the benefit of current and future generations. The USGS recognizes the need to make its information available to Tribal governments, and to work with those governments and other institutions to advance data management capabilities. The USGS is responding to this need by increasing the transfer of scientific information to American Indian and Alaska Native governments and by training employees of those governments to conduct and improve scientific studies. The USGS is also encouraging American Indians and Alaska Natives to pursue careers in science, and seeking ways to hire Indian and Native students. By identifying, improving, and disseminating information about available hiring mechanisms, the USGS is working to make hiring such students easier, and therefore more likely, for USGS managers. The U.S. Geological Survey is the Federal science bureau within the Department of the Interior (DoI). The USGS is non-regulatory and is not a significant manager of Federal or Trust lands or assets. However, there are two types of USGS activities that do involve American Indians, Alaska Natives, and their lands. The first type of activity is the course of formal studies, conducted through existing USGS programs, that involves collection of specific types of data as well as investigative and research projects. These projects typically last 2 or 3 years, although a few are parts of longer-term activities. Some projects are funded through cooperative agreements, from monies provided to the USGS by individual Tribal governments or by the BIA. The USGS provides matching funds for cooperative projects. These formal projects may also receive funding from the U.S. Environmental Protection Agency, the Indian Health Service (part of the Department of Health and Human Services), or other Federal agencies. The USGS routinely works with its sister bureaus in the Department of the Interior to provide the scientific information and expertise needed to meet the Department's science priorities. Within this context, the USGS and the BIA are cooperating to use USGS information resources to benefit American Indian and Alaska Native peoples and their lands. The second type of USGS activity is less formal, based on initiatives designed and conducted by USGS employees. Frequently involving educational activities, these endeavors are prompted by employee interests, often as collateral issues, that result from one or more USGS employees identifying and responding to an observed need. In these activities, USGS employees help fulfill a mission of the USGS-to make science relevant-while helping their fellow citizens. USGS employees have also taken the initiative in assisting American Indians and Alaska Natives through participation in several organizations that were created to foster awareness of science among Native peoples and to help build support and communication networks. One such group is the American Indian Science and Engineering Society (AISES). This group sponsors an annual national meeting in which USGS employees participate. USGS employees join this organization on a voluntary basis, bringing the benefits of this expanded network to the USGS, as many employees do with other professional organizations. Each part of the USGS has identified an American Indian/Alaska Native liaison. Furthermore, the USGS has instituted a regional organizational structure, with Western, Central, and Eastern Regions. The regions work in concert with specific scientific disciplines to conduct the scientific mission of the USGS. The regional structure is intended to bring us closer to our customers; we hope that Native Americans and Alaska Natives will use the contacts listed at the end of this report.

Report↗

USGS1989

Water-resources activities of the U.S. Geological Survey in Kansas; fiscal years 1987 and 1988

The principal mission of the U.S. Geological Survey, Water Resources Division, in Kansas is to investigate the occurrence, quantity, quality, distribution, and movement of surface and groundwater throughout the State. Primary activities include the systematic collection, analysis, and interpretation of hydrologic data, evaluation of water demands, and water resources research. Hydrologic investigations are conducted through four types of studies: (1) data collection programs; (2) statewide or regional investigations; (3) local or area investigations; and (4) research. These studies are funded through cooperative agreements with State and local agencies, transfer of funds from other agencies, and direct Federal funds. Thirty-six water related studies were ongoing during fiscal years 1987 and 1988 in Kansas. This report describes for each study the problem that initiated the study, the objectives of the study, the approach designed to achieve the objectives, and significant milestones and publications that resulted during fiscal years 1987 and 1988. Information on more than 2,100 data collection stations in Kansas is presented in maps and tables. A list of 46 reports and abstracts published or released by the U.S. Geological Survey, its cooperators, or technical and scientific organizations during 1987 and 1988 is provided. (USGS)

Open-File Report↗

USGS2006

Well construction information, lithologic logs, water level data, and overview of research in Handcart Gulch, Colorado: An alpine watershed affected by metalliferous hydrothermal alteration

Integrated, multidisciplinary studies of the Handcart Gulch alpine watershed provide a unique opportunity to study and characterize the geology and hydrology of an alpine watershed along the Continental Divide. The study area arose out of the donation of four abandoned, deep mineral exploration boreholes to the U.S. Geological Survey for research purposes by Mineral Systems Inc. These holes were supplemented with nine additional shallow holes drilled by the U.S. Geological Survey along the Handcart Gulch trunk stream. All of the holes were converted into observation wells, and a variety of data and samples were measured and collected from each. This open-file report contains: (1) An overview of the research conducted to date in Handcart Gulch; (2) well location, construction, lithologic log, and water level data from the research boreholes; and (3) a brief synopsis of preliminary results. The primary purpose of this report is to provide a research overview as well as raw data from the boreholes. Interpretation of the data will be reported in future publications. The drill hole data were tabulated into a spreadsheet included with this digital open-file report.

Colorado↗

USGS1985

Water-resources activities of the U.S. Geological Survey in Kansas; fiscal years 1983 and 1984

The principal mission of the U.S. Geological Survey, Water Resources Division, in Kansas is to investigate the occurrence, quantity, quality, distribution, and movement of surface and ground waters throughout the State. Primary activities include the systematic collection, analysis, and interpretation of hydrologic data, evaluation of water demands, and water-resources research. Hydrologic investigations are conducted through four basic types of projects: (1) data-collection programs, (2) local or areal investigations, (3) statewide or regional investigations, and (4) research projects. These projects are funded through cooperative agreements with State and local agencies, transfer of funds from other Federal agencies, and direct Federal funds. Fifty water-related projects were ongoing during fiscal years 1983 and 1984 in Kansas. This report describes for each of these water-resources activities the problem that initiated the study, the objectives of the project, and the approach designed to achieve these objectives. Information on data-collection stations in Kansas is presented in maps and tables. A list of the 40 reports approved for publication by the U.S. Geological Survey, its cooperators, or technical and scientific organizations during 1983 and 1984 is provided. (USGS)

Open-File Report↗

USGS1987

Water-resources activities of the U.S. Geological Survey in Kansas; fiscal years 1985 and 1986

The principal mission of the U.S. Geological Survey, Water Resources Division, in Kansas is to investigate the occurrence, quantity, quality, distribution, and movement of surface and groundwater throughout the State. Primary activities include the systematic collection, analysis and interpretation of hydrologic data, evaluation of water demands, and water resources research. Hydrologic investigations are conducted through: (1) data collection programs, (2) statewide or regional investigations, (3) local or areal investigations, and (4) research. These projects are funded through cooperative agreements with state and local agencies, transfer of funds from other federal agencies, and direct federal funds. Forty-three water related projects were ongoing during fiscal years 1985 and 1986 in Kansas. This report describes for each project the problem that initiated the study, the objectives of the project, the approach designed to achieve the objectives, and significant milestones or publications that resulted during fiscal years 1985 and 1986. Information on more than 2,150 data collection stations in Kansas is presented in maps and tables. A list of 47 project reports published or released by the U.S. Geological Survey, its cooperators, or technical and scientific organizations during 1985 and 1986 is provided. (Author 's abstract)

Open-File Report↗

USGS2018

GSFLOW-GRASS v1.0.0: GIS-enabled hydrologic modeling of coupled groundwater–surface-water systems

The importance of water moving between the atmosphere and aquifers has led to efforts to develop and maintain coupled models of surface water and groundwater. However, developing inputs to these models is usually time-consuming and requires extensive knowledge of software engineering, often prohibiting their use by many researchers and water managers, thus reducing these models' potential to promote science-driven decision-making in an era of global change and increasing water resource stress. In response to this need, we have developed GSFLOW–GRASS, a bundled set of open-source tools that develops inputs for, executes, and graphically displays the results of GSFLOW, the U.S. Geological Survey's coupled groundwater and surface-water flow model. In order to create a robust tool that can be widely implemented over diverse hydro(geo)logic settings, we built a series of GRASS GIS extensions that automatically discretizes a topological surface-water flow network that is linked with an underlying gridded groundwater domain. As inputs, GSFLOW–GRASS requires at a minimum a digital elevation model, a precipitation and temperature record, and estimates of channel parameters and hydraulic conductivity. We demonstrate the broad applicability of the toolbox by successfully testing it in environments with varying degrees of drainage integration, landscape relief, and grid resolution, as well as the presence of irregular coastal boundaries. These examples also show how GSFLOW–GRASS can be implemented to examine the role of groundwater–surface-water interactions in a diverse range of water resource and land management applications.

Geoscientific Model Development↗

USGS2001

National survey of MTBE and other VOCs in community drinking-water sources

Methyl tert -butyl ether (MTBE) is a volatile organic compound (VOC) that is added to gasoline either seasonally or year round in many parts of the United States to increase the octane level and to reduce carbon monoxide and ozone levels in the air. The chemical properties and widespread use of MTBE can result in contamination of private and public drinking-water sources. MTBE contamination is a concern in drinking water because of the compound's low taste and odor threshold and potential human-health effects. Because of this concern, a survey was initiated in collaboration with researchers and water suppliers. The purpose of this survey is to provide sound, unbiased, scientific information on the occurrence of MTBE and other VOCs in ground water, reservoirs, and rivers that are sources of drinking water used by communities of various sizes throughout the Nation. This fact sheet presents a general description of the survey.

Fact Sheet↗

USGS1992

Water-resources activities of the U.S. Geological Survey in Kansas; fiscal years 1989,1990, and 1991

The principal mission of the U. S. Geological Survey, Water Resources Division, in Kansas is to investigate the occurrence, quantity, quality, distribution, and movement of surface and ground water throughout the State. Primary activities include the systematic collection, analysis, and interpretation of hydrologic data, evaluation of water demands, and water-resources research. Four types of hydrologic investigations are conducted: (1) data-collection activities, (2) statewide or regbnal investigations, (3) local or areal investigations, and (4) research. These studies are funded through joint-funding agreements with State and local agencies, transfer of funds from other Federal agencies, and direct Federal funds. Forty water-related studies were ongoing during fiscal years 1989 through 1991 in Kansas. This report describes for each study the problem that initiated the study, the objectives of the study, the approach designed to achieve the objectives, and significant milestones and publications that resulted during fiscal years 1989-91. Information on more than 1,800 data-collection stations in Kansas is presented in maps and tables. A list of 81 reports and abstracts published or released by the U.S. Geological Survey, its cooperators, or technical and scientific organizations during calendar years 1989, 1990, and 1991 is provided.

Kansas↗

USGS2026

Network-wide assessment of soil water content calibration and sensitivity to biomass proxies using cosmic-ray neutron sensing in the Roaring Fork Basin, Colorado

Soil water content (SWC) is a key state variable of the climate system but is often uncertain in water balance monitoring, especially in alpine environments. SWC measurements can be challenging in alpine environments due to the topography and rocky soils. In 2022, the US Geological Survey's Next Generation Water Observing System Program began research to evaluate water balance monitoring technologies, including cosmic-ray neutron sensors (CRNS). This work evaluated the uncertainty resulting from network-wide calibration of CRNS for SWC monitoring in an alpine watershed and investigated the stability of the calibration parameters across space and time, focusing on potential influence of biomass dynamics. Fifteen stations with moderated and unmoderated (bare) CRNS were deployed and made operational within the Roaring Fork Basin in west-central Colorado. The root mean squared error of the network-wide calibration using the moderated CRNS was 0.042 or 0.047 cm 3 cm −3 , depending on the calibration equation used. Relative SWC dynamics from CRNS were correlated with the in situ probes with a correlation coefficient of 0.91 or 0.87 (depending on calibration equation). We did not find significant relationships between the calibration parameters and stationary site-specific variables. However, the calibration parameters derived from in situ probe SWC dynamics varied over time and were correlated with biomass proxies of cumulative growing degree-day, cumulative growing season index, and bare neutron counts. Future use of the CRNS network can leverage the reliable relative SWC data from network-wide calibration for watershed modeling and continue to research sensitivity of bare neutron measurements to biomass dynamics.

Colorado↗

USGS1983

Water-resources investigations of the U.S. Geological Survey in Kansas; fiscal years 1981 and 1982

One of the primary missions of the U.S. Geological Survey in Kansas is to investigate the occurrence, quantity, quality, distribution, and movement of surface and groundwater throughout the State. Primary activities include the systematic collection, analysis, and interpretation of hydrologic data, evaluation of water demands, and water-resources research. Hydrologic investigations are conducted through four basic types of projects: (1) data-collection programs, (2) local or areal investigations, (3) statewide or regional investigations, and (4) research projects. These projects are funded through cooperative agreements with State and local agencies, transfer of funds from other Federal agencies, and direct Federal funds. Forty-two water-related projects were funded during fiscal years 1981 and 1982 in Kansas. This report describes for each of these water-resources investigations the problem that initiated the study, the objectives of the project, and the approach designed to achieve this objective. Information on data-collection stations in Kansas is presented in maps and tables. A list of reports approved for publication by the U.S. Geological Survey, its cooperators, or technical and scientific organizations during fiscal years 1981 and 1982 is also provided. (USGS)

Open-File Report↗

USGS2008

Hydrogeologic Setting, Ground-Water Flow, and Ground-Water Quality at the Langtree Peninsula Research Station, Iredell County, North Carolina, 2000-2005

A 6-year intensive field study (2000-2005) of a complex, regolith-fractured bedrock ground-water system was conducted at the Langtree Peninsula research station on the Davidson College Lake Campus in Iredell County, North Carolina. This research station was constructed as part of the Piedmont and Mountains Resource Evaluation Program, a cooperative study being conducted by the North Carolina Department of Environment and Natural Resources and the U.S. Geological Survey. Results of the study characterize the distinction and interaction of a two-component ground-water system in a quartz diorite rock type. The Langtree Peninsula research station includes 17 monitoring wells and 12 piezometers, including 2 well transects along high to low topographic settings, drilled into separate parts of the ground-water-flow system. The location of the research station is representative of a metaigneous intermediate (composition) regional hydrogeologic unit. The primary rock type is mafic quartz diorite that has steeply dipping foliation. Primary and secondary foliations are present in the quartz diorite at the site, and both have an average strike of about N. 12 degree E. and dip about 60 degree in opposite directions to the southeast (primary) and the northwest (secondary). This rock is cut by granitic dikes (intrusions) ranging in thickness from 2 to 50 feet and having an average strike of N. 20 degree W. and an average dip of 66 degree to the southwest. Depth to consolidated bedrock is considered moderate to deep, ranging from about 24 to 76 feet below land surface. The transition zone was delineated and described in each corehole near the well clusters but had a highly variable thickness ranging from about 1 to 20 feet. Thickness of the regolith (23 to 68 feet) and the transition zone do not appear to be related to topographic setting. Delineated bedrock fractures are dominantly low angle (possibly stress relief), which were observed to be open to partially open at depths of as much as 479 feet below land surface. Well yields ranged from about 3 to 50 gallons per minute. The connection of fracture zones at depth was demonstrated in three bedrock wells during a 48-hour aquifer test, and drawdown curves were similar for all three wells. General findings of this study help characterize ground-water flow in the Piedmont and Mountains ground-water systems. Ground-water flow generally is from high to low topographic settings. Ground-water flow discharges toward a surface-water boundary (Lake Norman), and vertical hydraulic gradients generally are downward in recharge areas and upward in discharge areas. Dominant water types are calcium-bicarbonate and are similar in all three zones (regolith, transition zone, and bedrock) of the ground-water system. Results of continuous ground-water-quality monitoring indicate that ground-water recharge may occur seasonally over a period of several months or after heavy rainfall periods over a shorter period of a few to several weeks.

North Carolina↗

USGS2018

Maps showing predicted probabilities for selected dissolved oxygen and dissolved manganese threshold events in depth zones used by the domestic and public drinking water supply wells, Central Valley, California

The purpose of the prediction grids for selected redox constituents—dissolved oxygen and dissolved manganese—are intended to provide an understanding of groundwater-quality conditions at the domestic and public-supply drinking water depths. The chemical quality of groundwater and the fate of many contaminants is influenced by redox processes in all aquifers, and understanding the redox conditions horizontally and vertically is critical in evaluating groundwater quality. The redox condition of groundwater—whether oxic (oxygen present) or anoxic (oxygen absent)—strongly influences the oxidation state of a chemical in groundwater. The anoxic dissolved oxygen thresholds of <0.5 milligram per liter (mg/L), <1.0 mg/L, and <2.0 mg/L were selected to apply broadly to regional groundwater-quality investigations. Although the presence of dissolved manganese in groundwater indicates strongly reducing (anoxic) groundwater conditions, it is also considered a “nuisance” constituent in drinking water, making drinking water undesirable with respect to taste, staining, or scaling. Three dissolved manganese thresholds, <50 micrograms per liter (µg/L), <150 µg/L, and <300 µg/L, were selected to create predicted probabilities of exceedances in depth zones used by domestic and public-supply water wells. The 50 µg/L event threshold represents the secondary maximum contaminant level (SMCL) benchmark for manganese (U.S. Environmental Protection Agency, 2017; California Division of Drinking Water, 2014), whereas the 300 µg/L event threshold represents the U.S. Geological Survey (USGS) health-based screening level (HBSL) benchmark, used to put measured concentrations of drinking-water contaminants into a human-health context (Toccalino and others, 2014). The 150 µg/L event threshold represents one-half the USGS HBSL. The resultant dissolved oxygen and dissolved manganese prediction grids may be of interest to water-resource managers, water-quality researchers, and groundwater modelers concerned with the occurrence of natural and anthropogenic contaminants related to anoxic conditions. Prediction grids for selected redox constituents and thresholds were created by the USGS National Water-Quality Assessment (NAWQA) modeling and mapping team.

California↗

USGS2026

Local water use and climate variability drive water stress and alter ecological flows over the conterminous United States

Consistent, large-scale estimates of water availability are needed to identify and avoid potential conflicts among human and ecosystem uses of water. We present an assessment of water limitation, defined as the monthly balance (difference) between water supply ( ws ) and human consumptive water use ( wc ), for the conterminous United States (CONUS) during water years 2010–2020. We estimate that 26.7 million Americans, 8% of CONUS population, live in areas with chronic high or severe water limitation. Although ws greatly exceeds wc at the CONUS scale, water is limited locally or regionally due to spatial and temporal patterns in climate and wc . Our water limitation metric, the monthly supply and use index (SUI), peaked in 2012 during a widespread drought when 38% of the CONUS land area experienced elevated water stress. The central and Southwestern U.S. experienced the highest SUI due to the combination of low ws and high wc , especially for irrigation. Spatial overlays of SUI and fish habitat ranges, including those of conservation concern, revealed that several species had notable proportions of their habitat exposed to high or severe water limitation during spawning season over the modeled time period, especially the Arkansas River shiner. ws was calculated from two CONUS, physically-based, hydrologic models while wc was calculated from three CONUS models of water use for crop irrigation, thermoelectric power generation, and public supply. The ws and wc values were routed through a stream network and compared to calculate water limitation and SUI for human populations and fish species at the scale of 12-digit hydrologic unit codes. Evaluation of water availability at higher spatial and temporal resolution promotes more comprehensive analyses of the drivers of water availability and can be combined with complementary studies of water quality and water limiting thresholds to better understand the limitations on water availability.

conterminous United States↗