Triangle Area Water Supply Monitoring Project, North Carolina—Summary of monitoring activities, quality assurance, and data, October 2017–September 2019

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, from October 2017 through September 2018 (water year 2018) and from October 2018 through September 2019 (water year 2019). Major findings for this period include the following:

• More than 7,500 individual measurements of water quality were made at 20 sites—7 in the Neuse River Basin and 13 in the Cape Fear River Basin. For the lake sites, only measurements from the photic zone and 1 meter below the water surface are documented in this report.
• Thirty-six water-quality properties or constituents are presented in this report; the State of North Carolina water-quality thresholds are presented for 11 of these.
• All observations met the State of North Carolina water-quality thresholds for water temperature, hardness, chloride, fluoride, sulfate, and nitrate plus nitrite.
• The State of North Carolina water-quality thresholds were exceeded one or more times for dissolved oxygen, dissolved-oxygen percent saturation, pH, turbidity, and chlorophyll a.