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Onslow Water Quality Monitoring Program

White Oak River Basin map

Map of the White Oak River Basin in Onslow and Carteret

Onslow County is rather unique, particularly for a coastal county, in that no water enters from another county. Onslow’s New River (as opposed to the other New River in the northwestern portion of the state) begins and ends within Onslow. Water in the western portion of Onslow flows west toward the Cape Fear River. Water in the eastern portion of Onslow flows east toward the White Oak River. The remainder of the county supplies water to the New River. (See figure above.)

In 1999, the Onslow County Commissioners, with the aid of Senator Charlie Albertson, obtained $50,000 in funds to support an Onslow County Water Quality Study. This study had the following objectives:

  • Establish a 1-year water quality testing program in Onslow County to recognize the importance of improving all the waters in Onslow for the safety, health, and economic welfare of its citizens.
  • Determine what shellfishing, fishing, and anadromous fish spawning areas are impacted by fecal coliform, copper, arsenic, ammonia, and other pollutants.
  • Augment the efforts of NC Shellfish Sanitation and others to identify and possibly eliminate sources of pollution to County waters.
  • Inform area fishermen and residents of the results, how it impacts them, and what can be done to correct situations.
  • Develop specific recommendations for managing and maintaining the recreational and commercial uses of Onslow County waterways.

A local committee comprised of researchers, Health Department personnel, environmental groups, and others selected the initial sampling sites. Currently, there are 28 active monitoring sites (see pins in the maps below, click images to see larger versions of the maps). The Hydrologic Unit Area (HUA) map show the sub-basin drainage areas within Onslow.

Water program sampling sites

Onslow Water Quality Monitoring Program sampling sites

Hydrologic Unit Area map

Hydrologic Unit Area (HUA) map of Onslow County, showing the sub-basin boundaries.

The sampling sites cover most of the New River and White Oak sub-basins within Onslow and include a variety of land uses (e.g., agriculture, forestry, fishing/recreation, urban/residential). Sampling was begun at some of the sites during 1999. Sampling at most of the sites began in April 2000 and was to continue until at least March 2001. Prudent use of funds allowed the program to continue through June 2002.

Since then, the County Commissioners decided to continue the monitoring program. There are currently 28 sites being monitored. Reports are presented to the Onslow County Board of Commissioners at least annually. The following reports are available as pdf files:

The Onslow Water Quality Monitoring Program samples are analyzed for temperature, salinity, dissolved oxygen, enterococcus bacteria, nitrate-Nitrogen, ammonia-Nitrogen, and ortho-phosphate Phosphorus. Samples are collected every 2 weeks.

There is a USGS river gaging station on the New River at Northwest Bridge Rd. This gage is used for a variety of things, such as determining if there is too little (or too much) flow for paddling. The site has data for the past 50 years. On Tuesday, June 8th 2010, water depth, temperature, dissolved oxygen (DO), and salinity data were collected every 0.5 miles from Rhodestown Rd. (R4 site) to Rag Lane (J16 site). The goal was to locate “head of tide”. One definition of “head of tide” is “the farthest point upstream where a river is affected by tidal fluctuations.”  In this case, we were looking to see how far the salt water comes up the river above Jacksonville. The collected information was mapped and may be seen below:

“Click” on a pushpin to see the data for that location. From the data, “head of tide” appears to be near “Location 11”. The image below shows the tidal level of the New River when the data was collected. Data collection began at 9 a.m., and continued through 1 p.m. on 06/08/10.

water height graph

Water height measured at Northwest Bridge Rd.

Update: We redid our paddle from Rhodestown Rd. down to the New River estuary, taking samples along the way, on May 14, 2020. You can view the locations and data in the map below. Click on a “pin” to see the data.

We plan to do this a couple more times this year (summer and fall) – weather permitting.

A description of the State’s water quality classification system is available online.

Dr. Diana Rashash
Area Specialized Agent – Natural Resources
4024 Richlands Hwy.
Jacksonville, NC 28540
(910) 455-5873

Written By

Diana Rashash, N.C. Cooperative ExtensionDr. Diana RashashArea Specialized Agent, Water Quality / Waste Management Serves 18 CountiesBased out of OnslowCall Dr. Diana E-mail Dr. Diana N.C. Cooperative Extension, Onslow County Center
Page Last Updated: 3 months ago
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