Triangle area water supply monitoring project, North Carolina-Summary of monitoring activities, quality assurance, and data, October 2015–September 2017

Surface-water supplies are important sources of drinking water for residents in the Triangle area of North Carolina, which is located within the upper Cape Fear and Neuse River Basins. Since 1988, the U.S. Geological Survey and a consortium of local governments have tracked water-quality conditions and trends in several of the area’s water-supply lakes and streams. This report summarizes data collected through this cooperative effort, known as the Triangle Area Water Supply Monitoring Project, during October 2015 through September 2016 (water year 2016) and October 2016 through September 2017 (water year 2017). Major findings for this period include the following:

• More than 5,000 individual measurements of water quality were made at a total of 20 sites—7 in the Neuse River Basin and 13 in the Cape Fear River Basin. Only the measurements from the photic zone and 1 meter below the water surface are documented in this report.
• Twenty-nine water-quality properties or constituents are presented in this report; State water-quality thresholds exist for 11 of these.
• All observations met State water-quality thresholds for hardness, chloride, fluoride, sulfate, and nitrate plus nitrite.
• North Carolina water-quality thresholds were exceeded one or more times for dissolved oxygen, dissolved-oxygen percent saturation, pH, water temperature, turbidity, and chlorophyll a.