Background

Concerns about lake eutrophication and contaminants that affect drinking-water quality have remained priorities since the Project began.  Additional concerns have been addressed as they arose. Pesticides and PCBs, pharmaceuticals and other emerging contaminants, disinfection by-products, microbial pathogens such as Cryptosporidium and Giardia, mercury, and cyanotoxins also have been investigated during previous phases, and a series of USGS reports have been published.  The sustainability of water supplies depends on water availability as well as water quality; therefore, 10 streamflow-gaging stations are also supported by the Project.

TAWSMP Mission Statement

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Cane Creek Reservoir, Orange County, NC, 2003.

New public health concerns have recently emerged in the Triangle area related to probable carcinogens in drinking water.  From 2014-2016, high levels of bromide and 1,4-dioxane were reported in portions of the Cape Fear River basin; however, information is lacking for many of the water-supply sources in the Triangle area.  Bromide supports the formation of brominated trihalomethanes.  1,4-dioxane is an organic solvent that is a probable human carcinogen.  No Triangle area data are available for hexavalent chromium, another constituent of concern.  Water suppliers need additional information for these constituents; therefore, the USGS is investigating their occurrence and distribution in Triangle area water supplies while continuing the long-term monitoring program for conventional water-quality constituents.

Objective:

The project currently is in Phase IX, which spans the period July 1, 2022 -June 30, 2027. Water-quality and hydrologic monitoring from Phase VII will continue, with the addition of constituents of current concern to municipal water suppliers.

The objectives for Phase IX of the Monitoring Project are to:

  1. Characterize and report water quality monitoring results
    • Perform monitoring of major ions, nutrients, suspended sediment, and chlorophyll-a to document water-quality conditions throughout the study area and to extend the existing database that the USGS can use in the future to evaluate loads and trends.
    • Monitor the occurrence and distribution of additional parameters of concern to local water suppliers, including bromide and 1,4-dioxane at select sites (see Table 1), and per- and polyfluoroalkyl substances (PFAS) at all sites.
    • Summarize project water-quality data collection in annual data release updates comprising all environmental and QA/QC sample results.
  2. Characterize regional surface water availability
    • Provide information on flow conditions in reservoir tributaries by continuing to operate a network of 10 gaging stations for the collection of continuous streamflow data. Note that the USGS operates 2 additional gages at TAWSMP sites; they are funded by the U.S. Army Corps of Engineers rather than TAWSMP partners. All streamflow data will be made publicly available in real time at https://waterdata.usgs.gov/nc/nwis/rt.
  3. Develop interpretive science products to disseminate data and scientific findings
    • Produce a two-page fact sheet directed towards the public that TAWSMP partners can use to communicate the goals and benefits of the project
    • Publish a report summarizing the results from phases XIII and IX contaminant sampling (PFAS, 1,4-dioxane, bromide, and chromium).

Approach:

The USGS samples 9 lake sites and 4 stream sites six times per year. Dissolved oxygen, pH, water temperature, specific conductance, turbidity, nutrients, major ions (including bromide), chromium fractions, and 1,4-dioxane are sampled at all sites.  In addition, suspended sediment is monitored at stream sites.  Chlorophyll, water clarity, iron, and manganese are measured at lake sites. Eight additional streams in the study area are sampled by the North Carolina Department of Environmental Quality (DEQ) as part of their Ambient Monitoring System.  The USGS samples these sites during selected storm events on a rotational basis. As part of this project, the USGS also operates continuous-record streamflow gaging stations at 10 stream sites.

Quality-assurance measures include the use of clean sampling techniques, collection of numerous quality-control samples, and extensive data review. Samples are analyzed by the USGS National Water Quality Laboratory in Denver, Colorado, the USGS Eastern Region Sediment Laboratory in Louisville, Kentucky, and the USGS Redox Chemistry Laboratory in Boulder, Colorado. All data are permanently stored and made available to the public online through the USGS National Water Information System.

Long-term water-quality trends in the study area are currently being evaluated and will be published in a USGS Scientific Investigations Report. Water-quality constituents that will be analyzed for trends include nitrogen and phosphorus species, suspended sediment, chlorophyll, and selected major ions.

For a printable overview of the Project, please check out our one-pager here.