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North Carolina Water Science Center - "Of Current Interest" Archive
Archive of information featured in the "Of Current Interest" section of the NC WSC Home Page.
Station 02109500, Waccamaw River at Freeland, to be discontinued due to sequestration
Online: May 6, 2013
The U.S. Geological Survey (USGS) North Carolina Water Science Center will discontinue operation of Station Number 02109500 WACCAMAW RIVER AT FREELAND, NC due to budget cuts as a result of sequestration. This streamgage on the Waccamaw River has been continuously active since July 1939. If you have an interest in the collection of data at this gage, or are able to assist with funding, please contact Jeanne Robbins at email@example.com or (919) 571-4017.
Additional streamgages may be affected if partners reduce their funding to support USGS streamgages. The USGS is working to identify which, if any additional, streamgages will be impacted and will post this information as it becomes available. Streamgages are used nationwide to predict and address drought and flood conditions by monitoring water availability. The USGS and over 850 Federal, State, and local agencies cooperatively fund the USGS streamgaging network, which consists of over 8,000 streamgages.
NOTICE March 5, 2013 -- USGS to Discontinue Streamgages Due to Sequestration
Online: March 5, 2013
The U.S. Geological Survey (USGS) will discontinue operation of up to 375 streamgages nationwide due to budget cuts as a result of sequestration. Additional streamgages may be affected if partners reduce their funding to support USGS streamgages. The USGS is working to identify which streamgages will be impacted and will post this information as it becomes available. Streamgages are used nationwide to predict and address drought and flood conditions by monitoring water availability. The USGS and over 850 Federal, State, and local agencies cooperatively fund the USGS streamgaging network, which consists of over 8,000 streamgages. When budget fluctuations occur, the network is impacted.
Specific impacts to the North Carolina real-time network currently are not known.
New Publication: Determination of Flow Losses in the Cape Fear River
Online: January 30, 2013
Geoff Cartano (USGS) making discharge measurements at USGS station 02102240 Cape Fear River adjacent to Bay Street near Cokesbury, N.C., April 27, 2009
Exceprted from Abstract:
During 2008–2010, the U.S. Geological Survey conducted a hydrologic investigation in cooperation with the Triangle J Council of Governments Cape Fear River Flow Study Committee and the North Carolina Division of Water Resources to collect hydrologic data in the Cape Fear River between B. Everett Jordan Lake and Lillington in central North Carolina to help determine if suspected flow losses occur in the reach.
Analyses completed during this investigation indicate a study reach with complex flow patterns affected by numerous concurrent factors resulting in flow losses. The causes of flow loss could not be solely attributed to any one factor.
Losses by diversions and evaporation can exceed the median flow loss of 37 cubic feet per second, which indicates that flow loss from the study reach is real. Groundwater data collected during 2009–2010 indicate the possibility of localized flow loss during the summer, particularly in the impounded reach above Buckhorn Dam. However, no indication of unusual patterns was noted that would cause substantial flow loss by groundwater and surface-water interaction at the river bottom.
Full text of the report:
By J. Curtis Weaver and Kristen Bukowski McSwain
Questions regarding the report can be directed to Curtis Weaver, USGS, Raleigh, NC, at (919) 571-4043; e-mail firstname.lastname@example.org
USGS StreamStats application for North Carolina
Online: December 20, 2012
StreamStats for North Carolina, available at http://water.usgs.gov/osw/streamstats/north_carolina.html, is a Web-based Geographic Information System (GIS) application developed by the U.S. Geological Survey (USGS) in consultation with Environmental Systems Research Institute, Inc. to provide access to an assortment of analytical tools that are useful for water-resources planning and management. The StreamStats application provides an accurate and consistent process that allows users to easily obtain streamflow statistics, basin characteristics, and descriptive information for USGS data-collection sites and user-selected ungaged sites.
In the North Carolina application, users can compute 47 basin characteristics and peak-flow frequency statistics for a delineated drainage basin. Selected streamflow statistics and basin characteristics for data-collection sites have been compiled from published reports and also are immediately accessible by querying individual sites from the web interface.
The application was developed in cooperation with the North Carolina Department of Transportation and released to the public in June 2012.
Questions regarding the StreamStats application can be directed to Curtis Weaver, USGS, Raleigh, NC, at (919) 571-4043; e-mail email@example.com
Water in Two Counties to be Sampled and Studied before Possible Shale Gas Exploration
Online: November 15, 2011; updated December 1, 2011
Water from wells in Lee and Chatham counties will be sampled and tested for baseline information because of potential for shale gas exploration in these areas.
The baseline data collected from both private and public water supply wells will be used by state and local agencies to identify background concentrations of major ions, metals, volatile organic compounds, methane gas, and stable isotopes in the aquifer prior to increased shale gas exploration in North Carolina. If shale gas exploration occurs, this data will be used to compare to post-drilling water-quality samples.
Sampling of private wells can be requested from owners at no cost to them, and no well owner names or addresses will be made public. Both Lee and Chatham County Health Departments and supporting partners are providing well records that have been compiled as part of their permitting processes.
Questions regarding this sampling effort and water quality work in Lee and Chatham counties, or an interest in participating in the study, should be directed to Melinda Chapman, USGS, Raleigh, NC, at (919) 571-4047; e-mail firstname.lastname@example.org
The USGS prepares for Hurricane Irene
Online: August 25, 2011
The USGS North Carolina Water Science Center is deploying storm-surge sensors around the Outer Banks and coastal North Carolina to monitor the timing, extent, and magnitude of the storm surge following the passage of Hurricane Irene. The NCWSC is also preparing to make streamflow measurements at USGS real-time streamgaging stations.
Magnitude 5.8 earthquake in northern Virginia
Online: August 23, 2011
A magnitude 5.8 earthquake occurred in Virginia at 1:51 pm ET, 8/23/2011. The epicenter was 9 miles SSW from Mineral, VA and 36 miles NW from Richmond VA.
The Center for Earthquake Research and Information (CERI) researches earthquake activity in the Central and Eastern United States in cooperation with the USGS Earthquake Hazards Program.
Mecklenburg County rainfall distribution map released for the August 5, 2011 storm
Online: August 23, 2011
Rainfall contour maps are based on data from more than 70 raingages operated by the U.S. Geological Survey in cooperation with the City of Charlotte and Mecklenburg County as part of the Flood Information and Notification System (FINS). Information on the FINS raingage network is at http://nc.water.usgs.gov/char/rainfall.html. Real-time streamflow information also collected in the FINS network is at http://nc.water.usgs.gov/char/streamflow.html.
USGS National Research Program Guest Lecture Series: Using a Multi-Isotope Approach to Understanding Nutrient Sources and Cycling in Surface- and Groundwater
Online: October 8, 2010
Understanding nutrient and organic matter sources, sinks, and biogeochemical cycling is a critical component in environmental studies for both pristine and human-impacted systems. The scale and complexity of large hydrologic systems present logistical, financial, and interpretive challenges due to the difficulty of constraining both sources and biogeochemical dynamics. The use of a multi-isotope (H-C-N-O-S) approach in monitoring studies can provide critical insights into nutrient behavior over large spatial and temporal scales, highlighting both well-established and relatively new stable isotope methods. Studies in the San Joaquin River, Sacramento River, and San Francisco Bay demonstrate how the measurement of stable isotopes in water, nitrate, ammonium, phosphate, and particulate and dissolved organic matter can be used to constrain potential sources and sinks of nutrients, and identify biogeochemical processes that may not be evident through concentration analysis alone.
USGS Responds to Recent Flooding Resulting from Heavy Rain September 26 – October 1, 2010
Online: October 6, 2010
The USGS staff of the North Carolina Water Science Center responded to the drenching rains and resulting flooding by ensuring that USGS real-time gages were operational and providing critical information on river stage and rainfall to the public and emergency management officials. More than 40 streamflow measurements were also made at streamgages in central and eastern North Carolina to verify and update the site-specific relationships or rating between river stage and streamflow. These relationships are critical for determining the volume of water that passes a streamgaging station at any given river stage and are used in issuing flood warnings, mapping floodplains, monitoring water quality and environmental conditions and managing water resources.
Publication release: Nutrients in the Nation's streams and groundwater
Online: September 24, 2010 - October 8, 2010
A comprehensive national analysis of nutrients in streams and groundwater from 1992 through 2004 is now available from the National Water-Quality Assessment (NAWQA) Program of the USGS.
The information describes nutrient concentrations in the Nation's water resources, key sources of nutrients, factors affecting nutrient concentration, potential effects on humans and aquatic life, and changes in concentrations since the early 1990s. Implications of the findings touch on many environmental issues, including those related to (1) developing nutrient criteria for surface water bodies, (2) reducing nutrient loadings to receiving waters, (3) setting realistic expectations for water-quality improvements following nutrient reduction strategies, and (4) managing elevated nutrients in drinking water from surface-water intakes and wells.
Stormwater, Impervious Surfaces, and Stream Health
Online: September 10, 2010 - October 4, 2010
Urban development is associated with an increase in impervious surfaces, that is, surfaces such as rooftops, sidewalks, and streets that prevent precipitation from infiltrating into the groundwater. Impervious surfaces increase the volume and energy of stormwater that reaches streams and can lead to adverse physical and water quality impacts, including erosions and increased nutrient runoff. In this video USGS scientist Tom Cuffney and Tom Schueler, director of the Chesapeake Stormwater Network, discuss the effects of impervious surfaces on stream health.
The USGS Responds to Hurricane Earl
Online: September 2, 2010 to September 10, 2010
The USGS North Carolina (NC) Water Science Center in collaboration with scientists from NC Sea Grant, the University of North Carolina (UNC) Coastal Studies Institute, and the UNC Institute of Marine Sciences, has deployed storm-surge sensors around the Outer Banks and Pamlico Sound to monitor potential storm surge flooding from the passage of Hurricane Earl.
Storm surge associated with hurricanes occurs when winds push water up onto the shoreline. Historically, the magnitude of hurricane storm surge has been measured by using water lines, called high-water marks, left behind by flood waters. However, these sources are not always reliable or accurate and do not provide quantitative information about the timing of the flooding. In an effort to more accurately define the depth of storm surge as well as the duration, time of arrival and retreat, the U.S. Geological Survey has developed a program to deploy storm-surge sensors at locations that may be impacted by tropical systems. After the passage of the storm, the sensors will be retrieved, the data reviewed and elevation of the sensor determined relative to land surface. Data collected by the storm-surge sensors may be used in computer models (1) to estimate when, where, and to what degree storm-surge flooding will occur in future events and (2) to calibrate and verify storm-surge models, resulting in a better understanding of the dynamics of storm surge.
For more information on related activities, please see
2010 Water Resources Research Institute Annual Conference: State of Water Resources in North Carolina
Online: April 15, 2010 to September 2, 2010
The USGS was an active participant in the March 2010 WRRI conference, "State of Water Resources in North Carolina." The annual WRRI conferences allow participants to explore key issues, opportunities, and questions about North Carolina’s water resources; this year with over 40 presentations by university and corporate researchers, students, local, state and federal government agency representatives, and environmental professionals. This year the USGS was involved as one of the session organizers, as well as moderating a topical session and holding 2 poster sessions and 4 presentations.
WRRI Conference Presentations:
Geology of the Southern Appalachian Mountains
Online: March 8, 2010 to April 15, 2010
Created for use in high school and college classrooms, this new double-sided USGS map consists of a geologic map, photographs of geologic features, diagrams of plate movement, and more. The map is companion to the DVD and Teachers Guide The Southern Appalachians, a Changing World and the brochure Birth of the Mountains. Information about the Film, Teacher’s Guide, Booklet, and Geologic Map is summarized in a pdf file.
Widespread Occurrence of Intersex Bass Found in U.S. Rivers
Online: September 16, 2009 to March 8, 2010
Intersex in smallmouth and largemouth basses is widespread in numerous river basins throughout the United States is the major finding of the most comprehensive and large-scale evaluation of the condition, according to U.S. Geological Survey (USGS) research published online in Aquatic Toxicology.
Of the 16 fish species researchers examined from 1995 to 2004, the condition was most common by far in smallmouth and largemouth bass: a third of all male smallmouth bass and a fifth of all male largemouth bass were intersex. This condition is primarily revealed in male fish that have immature female egg cells in their testes, but occasionally female fish will have male characteristics as well.
Scientists found intersex fish in about a third of all sites examined from the Apalachicola, Colorado, Columbia, Mobile, Mississippi, Pee Dee, Rio Grande, Savannah, and Yukon River basins. The Yukon River basin was the only one where researchers did not find at least one intersex fish.
Although intersex occurrence differed among species and basin, it was more prevalent in largemouth bass in southeastern U.S., where it occurred at all sites in the Apalachicola, Savannah, and Pee Dee river basins, said Jo Ellen Hinck, the lead author of the paper and a biologist at the USGS Columbia Environmental Research Center. The researchers also documented intersex in channel catfish for the first time.
“Although the USGS has already documented the severity of intersex in individual basins such as the Potomac, this study reveals the prevalence of intersex is more widespread than anyone anticipated,” said Sue Haseltine, associate director for biology at the U.S. Geological Survey. “This research sends the clear message that we need to learn more about the hormonal and environmental factors that cause this condition in fish, as well as the number of fish afflicted with this condition.”
The study, said Hinck, presents the observed occurrence of intersex in a variety of freshwater fish species, but not potential causes. “This study adds a lot to our knowledge of this phenomena, but we still don’t know why certain species seem more prone to this condition or exactly what is causing it. In fact, the causes for intersex may vary by location, and we suspect it will be unlikely that a single human activity or kind of contaminant will explain intersex in all species or regions,” she said.
For example, said Hinck, at least one of their sites with a high prevalence of intersex—the Yampa River at Lay, Colo.—did not have obvious sources of endocrine-active compounds, which have been associated with intersex in fish. Such compounds are chemical stressors that have the ability to affect the endocrine system and include pesticides, PCBs, heavy metals, household compounds such as laundry detergent and shampoo, and many pharmaceuticals. Yet other study sites with high occurrence of intersex were on rivers with dense human populations or industrial and agricultural activities, which are more generally associated with endocrine-active compounds.
“We know that endocrine-active compounds have been associated with intersex in fish, but we lack information on which fish species are most sensitive to such compounds, the way that these compounds interact to cause intersex, and the importance of environmental factors,” Hinck said. “Proper diagnosis of this condition in wild fish is essential because if the primary causes are compounds that disrupt the endocrine system, then the widespread occurrence of intersex in fish would be a critical environmental concern.”
Specific river basin results include:
Photos for this release:
Visit: http://gallery.usgs.gov/tags/NR2009_09_14 for all available photos.
Release of North Carolina Hydrologic Alert System
Online: September 14, 2009 to September 16, 2009
The USGS North Carolina Water Science Center is pleased to release the North Carolina Hydrologic Alert System (NC-HAS).
NC-HAS provides real-time email or text message alert notifications when user-specified thresholds are met at USGS data-collection sites in North Carolina. NC-HAS is a customizable system provided free to everyone. You can receive email or text message notifications when the river stage or streamflow either exceeds or falls below your specified threshold at your site of choice. Likewise, alerts can be established for cumulative 1-, 2-, 4-, 6-, or 12-hour precipitation amounts.
Multiple alerts can be established. Alerts can be received at 15-minute, hourly, or daily intervals.
Data collection sites can be selected from a clickable map, or site numbers can be entered manually in the subscription form.
This is the first USGS hydrologic alert system of its kind in the Nation. We encourage you to test the system and to provide us with any feedback you have through the feedback link on the NC-HAS web page, which is at http://nc.water.usgs.gov/alert/.
USGS: Your Resource During Hurricane Season
Online: August 10, 2009 to September 14, 2009
Science that Weathers the Storm…
When hurricanes strike, you can find critical information to help protect lives and property at the U.S. Geological Survey (USGS) hurricane Web site.
More than half of the U.S. population lives within 50 miles of a coast — and coastal populations are increasing. Many of these areas, especially the Atlantic and Gulf coasts, will be in the direct path of hurricanes.
“Throughout hurricane season, reliable scientific information is essential in order for emergency managers to keep the American public safe,” said Secretary of the Interior Ken Salazar. “The USGS provides this science, which helps prevent hazards from becoming disasters.”
The USGS hurricane Web site highlights important storm information, such as flood levels near your home; pictures of the coastline before and after the storm; information on the timing, extent and magnitude of storm tide; and much more.
USGS research and analysis supports the National Oceanic and Atmospheric Administration (NOAA), which is responsible for monitoring and issuing warnings for hurricanes and tropical storms in the United States and its territories. Science to forecast hurricane impacts is a collaborative effort among the USGS, NOAA, NASA, the U.S. Army Corps of Engineers and others.
The USGS strives to reduce the vulnerability of the people and areas most at risk from natural hazards. By working with people from all sectors of society, the USGS and its partners are taking action to prepare for this year’s hurricane season. The USGS anticipates that these actions will provide many benefits, including improved monitoring of ground conditions affected by flooding and storm surge, enhanced ability to navigate in a disaster zone, more effective search and rescue operations, and better assessments of the effects on coastlines and ecology.
The USGS provides information, products and knowledge to help build more resilient communities and strives to keep America safe from natural hazards. For direct access to USGS hurricane-related efforts, visit the USGS Science: Before, During and After the Storm Web site.
Water Quality in Carbonate Aquifers in the United States
Online: July 14, 2009 to August 10, 2009
The USGS has released a new report, Factors affecting water quality in selected carbonate aquifers in the United States, 1993-2005 (available at http://water.usgs.gov/nawqa/pubs/carbonate/ with maps and other companion materials).
USGS scientists sampled for 151 chemical constituents or physical properties in about 1,000 wells and springs across 20 states, mainly in the eastern and central United States, and including North Carolina. The majority of the wells sampled in the study are used as drinking water sources, either for domestic or public supply. Therefore, these results are particularly relevant to drinking-water quality issues. Carbonate aquifers are the largest sources of drinking water for public supply of any bedrock aquifer, providing about 20 percent of the groundwater supplied as drinking water to the Nation.
In general, findings show that carbonate aquifers provide water of acceptable quality for human use and consumption in the majority of wells sampled across the U.S. With few exceptions, chemicals detected in groundwater from carbonate aquifers were low, generally below human-health benchmarks. Radon and nitrate were among the few contaminants with elevated concentrations in samples from wells tapping these important aquifers.
USGS findings show that the types and concentrations of selected contaminants in groundwater in carbonate aquifers are closely related to land use, such as fertilizers, pesticides, and volatile organic compounds (or VOCs). For example, concentrations of nitrate were significantly higher in groundwater underlying agricultural land than in groundwater underlying undeveloped or urban land. Herbicides were detected more frequently in agricultural wells, whereas insecticides and VOCs such as chloroform were more frequently detected in urban wells. Only 2 of the 47 pesticides analyzed exceeded human-health benchmarks in 20 sites and 4 of the 59 VOCs in 5 sites analyzed exceeded federal drinking-water standards.
Findings also show that factors other than land use can affect groundwater quality. For example, natural geochemistry is a factor influencing radon occurrence. Radon concentrations exceeded the proposed drinking-water standard of 300 picocuries per liter in 58 percent of the samples where radon was analyzed. Natural factors controlling aquifer confinement, groundwater residence times, and the presence of organic carbon can help to minimize the transport of contaminants to an aquifer or enhance degradation of contaminants to innocuous forms prior to entering wells.
USGS Estimates Nitrogen Loading to Streams and Coastal Areas of North Carolina and the Southeast
Online: June 29, 2009 to July 14, 2009
The U.S. Geological Survey National Water-Quality Assessment (NAWQA) program assessed total nitrogen loads and yields in streams throughout the southeastern United States using the USGS watershed model SPARROW (Spatially Referenced Regression On Watershed Attributes).
Results from the southeast regional total nitrogen SPARROW model indicate that atmospheric deposition is the largest source of nitrogen delivered annually to many estuaries along the South Atlantic and Gulf Coasts, such as Mobile and Apalachicola Bays.
The regional model integrates Federal, State, and local agency monitoring data at 321 stations with geospatial data describing 2002 nitrogen sources (fertilizer, animal waste, and urban inputs, atmospheric deposition, and wastewater discharges) and watershed properties (soil characteristics, precipitation, and land cover). The combination of more calibration sites and refined geospatial data provides significant improvement over previous SPARROW models in prediction accuracy and the identification of regional nutrient sources and transport factors.
Results of this study are described in the journal Hydrological Processes article and detailed supplemental tables with model predictions for instream load and yield for 8,028 stream reaches and 293 shoreline reaches and the fraction of instream load that is delivered to the basin outlet.
Results from the southeast regional SPARROW model can be used to assess:
For more information on nitrogen loading and delivery to streams and coastal areas in North Carolina, contact Ana Maria Garcia (email@example.com); for questions about other areas of the southeast, contact Anne Hoos, (firstname.lastname@example.org)
USGS Releases New Data and Studies for Predicting Nitrogen Removal in Streams
Online: June 4, 2009 to June 29, 2009
Results of two new studies led by USGS scientists are available in a special issue of the journal Biogeochemistry, which highlights findings from a workshop sponsored by the National Science Foundation on new approaches to modeling denitrification—an ecologically important bacterial process that converts reactive nitrogen compounds to inert nitrogen gas. Information about the studies can be found at http://water.usgs.gov/nawqa/sparrow/biogeochem/.
The two studies, conducted in collaboration with scientists in universities and other federal agencies, report on physical, biochemical, and land-use factors that can affect the spatial variability and seasonality in nitrogen removal by denitrification in agricultural and forested streams.
The findings show that the fraction of nitrogen removed by denitrification depends upon the nitrogen concentration in a stream, and, specifically, that relatively small proportions are removed in streams with elevated concentrations.
Unfortunately, nitrogen concentrations are highest in many agricultural streams in the winter and spring. This is the time when many streams also have high flows and export the largest amounts of nitrogen to coastal estuaries and other receiving waters. Excessive nitrogen can result in the growth of large amounts of algae and a zone of low dissolved oxygen (hypoxia), which can stress aquatic life in receiving waters, such as the northern Gulf of Mexico and Chesapeake Bay.
The new studies may contribute to more accurate model-based watershed assessments, which currently assume that the proportion of nitrogen removed by denitrification is unaffected by the levels of nitrogen concentration in streams. In addition, the findings provide scientific support for targeting nutrient management strategies in watersheds with relatively high nitrogen levels, where in-stream denitrification is expected to be least efficient.
Landmark U.S. Geological Survey Study Demonstrates How Methylmercury, Known to Contaminate Seafood, Originates in the Ocean
Online: May 8, 2009 to June 4, 2009
A U.S. Geological Survey (USGS) scientist and his university colleagues have discovered a new source of methylmercury entering the waters of the eastern North Pacific Ocean. Consumption of ocean fish and shellfish account for over 90 percent of human methylmercury exposure in the United States, and tuna harvested in the Pacific Ocean account for 40 percent of this total exposure. Given the obvious importance of marine food webs to human methylmercury exposure, scientists were still trying to answer the question - where do fish, such as Pacific Ocean tuna, acquire their methylmercury? The findings of these scientists, published in the journal Global Biogeochemical Cycle, presents the first evidence linking current atmospheric mercury deposition to methylmercury in Pacific Ocean fish. Additional information is available at http://toxics.usgs.gov/highlights/pacific_mercury.html.
Differences in Phosphorus and Nitrogen Delivery to the Gulf of Mexico from the Mississippi River Basin
Online: May 8, 2009 to June 4, 2009
Mississippi/Atchafalaya River Basin Watersheds
Each of the 818 large watersheds in the Mississippi/Atchafalaya River Basin (MARB) has been ranked on the basis of SPARROW model estimates of nitrogen and phosphorus yields delivered to the Gulf of Mexico by the U.S. Geological Survey (USGS), in cooperation with the U. S. Environmental Protection Agency (EPA). Uncertainties in the nutrient yield estimates from the MARB SPARROW model by Alexander and others, 2008, were incorporated into a statistical ranking procedure to determine the probability that a watershed is within the top 150 delivering the highest nutrient yields to the Gulf.
Model findings show that 11 watersheds are reliably placed in the top 150 category for total nitrogen (3 for total phosphorus) delivered to the Gulf of Mexico with 90 percent certainty. Although only a few watersheds could be placed into the top 150 category, numerous watersheds could be removed from consideration of being in the top 150 category. A total of 513 watersheds for total nitrogen and 505 watersheds for total phosphorus are reliably placed outside of the top 150 category with 90 percent uncertainty. Additional information is available at http://water.usgs.gov/nawqa/sparrow/nutrient_yields/.
Water Quality of Potential Concern in US Private Wells
Online: April 22, 2009 to May 8, 2009
More than 20 percent of private domestic wells sampled nationwide contain at least one contaminant at levels of potential health concern, according to a study by the U.S. Geological Survey (USGS).
About 43 million people - or 15 percent of the Nation's population - use drinking water from private wells, which are not regulated by the Federal Safe Drinking Water Act. In North Carolina, about 2.3 million people, or more than 25 percent of the State, obtain drinking water from private wells.
USGS scientists sampled about 2,100 private wells in 48 states and found that the contaminants most frequently measured at concentrations of potential health concern were inorganic contaminants, including radon and arsenic. These contaminants are mostly derived from the natural geologic materials that make up the aquifers from which well water is drawn. Complete findings are available online.
The study shows that the occurrence of selected contaminants varies across the country, often following distinct geographic patterns related to geology, geochemical conditions, and land use. For example, elevated concentrations of nitrate were largely associated with intensively farmed land, such as in parts of the Midwest Corn Belt and the Central Valley of California. Radon was found at relatively high concentrations in crystalline-rock aquifers in the Northeast, in the central and southern Appalachians, and in central Colorado.
Private well owners, who generally are responsible for testing the quality of their well water and treating, if necessary, can contact local and State health agencies for guidance and information about well maintenance and siting, water quality and testing options, and in-home water treatment devices. Access the Quality of Water from Domestic Wells in the United States Web site for related links to sources of information and recommendations for private well owners.
Mercury Cycling in Stream Ecosystems
Online: March 30, 2009 to April 22, 2009
Three related U.S. Geological Survey (USGS) articles on mercury transport, biogeochemical processes, and bioaccumulation in eight stream ecosystems have been published in Environmental Science & Technology (ES&T). The papers were published electronically on the March 11, 2009 in the “Just Published (ASAP)” web version of ES&T, and will be published in final form in the April 15, 2009 print issue.
An ES&T news story (http://pubs.acs.org/doi/full/10.1021/es9005916) highlights selected findings from these papers.
Publications and data from this study can be accessed electronically at http://water.usgs.gov/nawqa/mercury/pubs/.
All eight streams received mercury predominantly via atmospheric deposition, but watershed characteristics primarily determine mercury transport and bioaccumulation in these streams. Key factors include (1) the abundance of wetlands, which influence how much of the atmospherically deposited mercury is converted to methylmercury (the most toxic, bioaccumulative form of mercury); and (2) runoff of dissolved organic carbon and suspended sediment, which control how much mercury and methylmercury is delivered to the streams.An unexpected finding was that methylmercury production in channel sediments appears to be relatively unimportant for governing within-stream methylmercury levels.