Swim Guide by the Numbers

Swim Guide: By the Numbers

Starting Memorial Day Weekend, Sound Rivers sampled popular recreation sites each week to bring recreational water quality recommendations to the public based on fecal bacteria indicators. Our network of volunteers coordinated by our two interns, Katie McQuillan on the Lower Neuse River and Duncan Anderson on Tar-Pamlico River, collected enough data to make some assessments on basin health. On the Tar-Pamlico, we found that, on average, sites pass the EPA bacterial standard 74% of the time, with most of the regular failures occurring at Bath Creek, Broad Creek, and the Pungo River near Woodstock Point.

Overall the level of bacteria in the Lower Neuse has been slightly better than the Tar-Pamlico, with samples coming back healthy 89% of the time. Seven sampling sites were healthy 100% of the time. Of the sampling sites with routinely high levels of bacteria, all were located on the Trent River and the majority occurred at River Bend, but Brices Creek, Lawson Creek Park, and Pollocksville also revealed high levels of bacteria during the summer.

For both basins, we have compared our bacterial numbers to precipitation, evaluating to see if heavy rainfall prior to sampling (that could lead to polluted runoff into streams and rivers) is an effective indicator that a site sample will come back with high levels of bacteria. At the Tar-Pamlico problematic sites, and the Trent River at River Bend, there was a weak relationship between these metrics, meaning  there were many days where high bacterial levels appeared without large amounts of rain leading up to sampling. This suggests that the elevated levels of bacteria may be from localized wildlife and/or improper boat fecal disposal.

Brices Creek, Lawson Creek Park, and Pollocksville sites displayed a strong relationship between rain prior to sampling and fecal bacteria levels, indicating stormwater runoff from the surrounding area is a contributor to fecal bacteria pollution. Based on these results, we can determine that while rain before sampling was sometimes a good indicator of fecal bacteria levels, other more localized sources also played an important role.

This summer, we’ve been able to engage with thousands of members of the public each week with our results and through our volunteers. We’re currently working on securing funding to make this a recurring program each summer and to expand it to the Raleigh area. We hope the community will look for  Swim Guide next summer!