How Safe Are the Bays for Swimming?

by Dave on July 28, 2010

2010 Recreational Water Quality Report Released by the Center for the Inland Bays

Whether it’s swimming, paddling, or wading along the shoreline, the waters of the Inland Bays offer cool relief during the hot days of summer. More people than ever are enjoying the Bays as the local population grows, and ecotourism increases in popularity.

To help educate and inform people about the water quality of the Bays for swimming, the Center for the Inland Bays has published the second edition of its Recreational Water Quality Report.

From 2004 to 2009, more than 30 locations on Rehoboth, Indian River, and Little Assawoman Bays were tested for Enterococcus, an organism that can indicate the presence of potentially harmful waterborne bacteria and pathogens. Water with levels above the State standard for Enterococcus can expose swimmers to an increased risk of stomach illness.

Recreational water quality in the Bays was found to be very different depending on location:

• Open bay shores had good water quality, and only occasionally exceeded State water quality standards for bacteria.
• Bay tributaries, such as Dirickson Creek on Little Assawoman Bay and Guinea Creek on Rehoboth Bay, had poor water quality and regularly exceeded State water quality standards, often at high levels.

The State of Delaware has posted signs around the Bays to caution bay users about the risk of illness from swimming. Ed Whereat of the Citizen Monitoring Program said, “Bacteria levels are naturally variable and can be unpredictable at a given location.”

Studies suggest that bacteria levels are often higher after rains and on outgoing tides within tributaries. “The tidal tributaries have more bacteria because they are in closer connection to pollution from the land, and their waters are lower in salinity; freshwater is more hospitable to bacteria than salt water”, said Chris Bason, Science Coordinator for the CIB.

Is Water Quality Improving in the Inland Bays?
Data did not indicate any increasing or decreasing trends in bacteria levels, although 2009 had particularly high levels at many locations.

According to Bason, “When we think about how to keep our bays safe for swimming, we should keep in mind that some things can be controlled and some can’t. We need the help of everyone in the watershed to improve water quality in the Bays. We can’t do much about the fact that the bays are not well flushed by ocean water, or the fact that we share the bays with geese and gulls. But we can clean up after our pets, maintain our septic systems, and promote using pervious surfaces in communities – all these efforts can reduce bacteria levels.”

The report uses data collected by the University of Delaware Citizen Monitoring Program and the Department of Natural Resources and Environmental Control (DNREC) to illustrate how frequently bacterial levels in the Bays exceed the State water quality standards for swimming.
The report is available online at along with links to further information and more frequent water quality reports from the UD Citizen Monitoring Program and DNREC.

For more information, contact Sally Boswell, Education and Outreach Coordinator of the DE Center for the Inland Bays at (302) 226-8105.

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