Autonomous Underwater Vehicle Water-Quality Measurements in the Cape Fear River, multiple locations, North Carolina, 2020-2021

The Cape Fear River Basin was added to a nationwide program called The Sustainable Rivers Program (SRP) in 2016. SRP is a joint program between The Nature Conservancy (TNC) and the Army Corps of Engineers (Corps) to improve the health of rivers by analyzing how the Corps operates their infrastructure, such as the release of water out of dams. The SRP attempts to analyze the effects from dams and use reservoir operations to enhance and manage downstream (and sometimes in lake) ecosystems. Once a river is in the program, it goes through a formal process to consider e-flows for a basin. This includes gathering technical stakeholders to discuss the issues and potential solutions in the basin, compiling a literature review to gather information about pre- and post-dam conditions, hosting an e-flow (environmental flow) workshop to draft e-flow prescriptions, modeling the e-flow prescriptions, testing an e-flow, studying the outcomes, and eventually finding a way to make the e-flow part of regular operating procedures. The Cape Fear River Basin was chosen because of its complex human-ecology relationships, the expert stakeholders in the basin, and because the Corps-owned B. Everett Jordan Dam (Jordan Dam) has potential to influence fish and wildlife habitat, water quality, and other natural resources. The Cape Fear River Basin contains over two million people (2010 census), one-fifth of the state’s population. This includes growing urban areas of Durham, Greensboro, Pittsboro, Fayetteville, Wilmington and other cities, which contribute urban runoff into the river, but many of which also get a portion of their drinking water from this waterbody. The basin also supports 95 species of recreational fish, 42 rare aquatic species, as well as streamside habitat containing some of the oldest trees east of the Rocky Mountains; some of which are over 2000 years old (Stahle and others, 2012). Natural and human environments rely on the Cape Fear River, making its water quality and water quantity of the utmost importance.

This U.S. Geological Survey (USGS) data release presents water-quality and bathymetric data measured with an Autonomous Underwater Vehicle (AUV) during spatial surveys in the Cape Fear River near Lock and Dam 1 near Riegelwood, NC in 2020 and at the confluence of the Haw and Deep Rivers near Moncure, NC in 2021. The Cape Fear River Basin is contained entirely within North Carolina and has a drainage area of 3,464 square miles. Four data collection trips were conducted that included 21 surveys. Data from each survey are presented in a CSV file, named with the survey date, time, and location. Data were measured by the AUV and logged at 0.25-second intervals. The AUV was equipped with a YSI EXO1 multiparameter sonde with sensors to measure the following water-quality parameters: water temperature (degrees Celsius; YSI Sensor 599870), specific conductivity (microSiemens per centimeter at 25 degrees Celsius; YSI sensor 599870), phycocyanin fluorescence (relative fluorescence units; YSI sensor 599102-01), chlorophyll fluorescence (relative fluorescence units; YSI sensor 599103-01), dissolved oxygen (milligrams per liter; YSI sensor, 599100-01), and turbidity (formazin nephelometric units; YSI sensor 599101-01) (YSI, 2019). Sensors were calibrated before and checked after, each data collection trip per USGS water-quality sampling protocols (YSI, 2019; Wagner and others, 2006; U.S. Geological Survey, 2018). See Data Quality section for additional information related to calibration and checks. Bathymetric data were measured with an on-board depth sounder and pressure transducer. Parameters include depth from surface, depth to bottom, and total water column. See Data Quality section for additional information related to positional accuracy and corrections.