Project Overview

Full Title
Triangle Area Water Supply Monitoring Project

Location
 Chatham, Durham, Granville, Orange, and Wake Counties

Partner Agencies
Partner Agencies

Project Chief
Mary Giorgino
giorgino@usgs.gov

Period of Project
October 1988 - June 2017

Team Members
Jessica Cain
Cassandra Pfeifle
Ryan Rasmussen

Science Topic
Increased Population and Water Resources

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Triangle Area Water Supply Monitoring

Project Summary

Cane Creek Reservoir, Aug. 15, 2003

Background

Concerns about the effects of development on reservoir eutrophication and contaminants have remained prominent since the Project began in 1988. Additional concerns have evolved over time. The initial focus of the Project was on measuring pesticides, PCBs, and other synthetic organic compounds in water and sediment. Later efforts focused on analyzing nutrient and sediment loads and trends. Issues such as the occurrence of disinfection by-products, microbial pathogens such as Cryptosporidium and Giardia, U.S. Environmental Protection Agency (USEPA) priority pollutants, and pharmaceuticals and other emerging contaminants also have been addressed during different phases of the project.

Objectives

The project currently is in Phase VII, which spans the period July 2012-June 2017. Specific objectives for this phase are to:

1. Extend the existing data base for major ions, nutrients, sediment, trace elements, and chlorophyll a through June 2017 to provide data necessary for determining water-quality conditions throughout the study area, loads to reservoirs, and water-quality trends.
2. Operate a network of 10 stations for the collection of continuous streamflow data and make the data available in real time at http://waterdata.usgs.gov/nc/nwis/rt.
3. Conduct an investigation of the occurrence and distribution of algal toxins and taste and odor compounds at seven water-supply sites. An interpretive summary report will be published.

Approach

The USGS routinely samples 13 stream and reservoir sites in the study area. Seven reservoir sites are sampled by the USGS four to six times per year for nutrients, major ions, iron, manganese, and chlorophyll, and twice per year for metals and trace elements. Four stream sites are sampled by the USGS six times per year for nutrients, major ions, and suspended sediment, and twice per year for trace elements. Eight additional sites are sampled by the North Carolina Division of Water Quality (DWQ) as part of the North Carolina Ambient Monitoring Network and(or) by the USGS during selected storm events. 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 selected commercial laboratories. 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 and metals.

Reconnaissance of cyanotoxins, taste and odor compounds, and phytoplankton

Water-supply reservoirs in the Triangle Area range from mesotrophic to highly eutrophic. Phytoplankton vary seasonally and among locations, and algal blooms occasionally are observed. Blooms are aesthetically displeasing, discourage recreation, increase water-treatment costs, and may produce complex mixtures of toxins and taste-and-odor compounds. In particular, certain cyanobacteria ("blue-green algae") produce toxins that target the nervous system and liver of mammals and adversely affect a range of other organisms. These toxins include microcystins, cylindrospermopsin, anatoxin-a, and saxitoxins. Cyanobacteria also produce geosmin and 2-methylisoborneol (MIB), two organic compounds responsible for "musty" or "grassy" taste and odor complaints in drinking water.

To assess whether cyanotoxins and taste and odor compounds occur at levels of concern, the USGS will collect a series of additional samples at five reservoir sites during April-October 2014. Samples will be analyzed for four classes of cyanotoxins (microcystins, cylindrospermopsin, anatoxin-a, and saxitoxins) and two taste and odor compounds (geosmin and MIB). Phytoplankton samples will be analyzed for taxonomic identification, enumeration, and biovolume estimates. An interpretive report will be published that describes the occurrence and distribution of cyanotoxins and taste and odor compounds in relation to water-quality variables and phytoplankton assemblages.