July Riverkeeper Report

I know what you're thinking and no, it's not just you – all of our bacteria testing sites are having a bad season! By this time last year, our average passing rate for bacteria monitoring was 81%. This year, our pass rate is only about 45%. This high heat with intense and heavy rain events is certainly having an impact on our water quality. Arundel Rivers' waterways aren't alone in this trend- we have also seen high bacteria numbers from our partner organizations such as Spa Creek Conservancy and ShoreRivers on the Eastern Shore. This is a good reminder that you should not swim after rainfall of more than .5 inch or more. An analysis of our 2024 data showed that 88% of our samples failed after a rainfall event within the previous 48 hours. Looking at the rainfall data this year- 6 of the 8 sampling days have had previous rainfall of over a half inch. 

Because we have been consistently seeing poor results this year, I have been receiving more questions about how we run our program. Arundel Rivers staff and trained volunteers collect samples every Thursday morning– rain or shine. We take samples Thursday mornings to ensure that we get results out prior to the weekend, when we anticipate interaction with our waterways will be highest. We collect our samples at knee depth, again- where we anticipate interaction with beach to be the highest. I want to collect the samples where I know my 4 year old would be swimming– right around knee depth. Collected samples are then taken to Anne Arundel Community College, where they are processed and incubated overnight. Lab students count the number of colony forming units (cfu) after incubation and post the results Friday afternoon. Values below 104cfu/100ml are considered safe for swimming (a threshold recommended by the EPA). Arundel Rivers posts these results on our social media pages and on swimguide.org. 

Our testing program is slightly different from the Anne Arundel County testing program, which posts their results on MD Healthy Beaches. We both test for enterococci, bacteria that are found in the intestine of all warm-blooded animals, including humans. Enterococci can be an indicator of fecal contamination in the water, which may result in swimmers getting sick. We also both test at knee depth. The difference between our programs can be in the frequency of testing. Arundel Rivers will collect a sample every Thursday morning no matter what while the County only collects samples if there has been no prior rainfall of a half inch or more in the previous 48 hours.  The County also classifies certain beaches into 3 different tiers, which determine if a location is sampled either weekly, bi-weekly or monthly.  Beaches that cannot be sampled due to rainfall are moved to the next possible sampling day Monday through Wednesday. 

Learn More About Our Bacteria Monitoring Program

Being able to have both data from the County and Arundel Rivers provides a more complete picture to help you determine if it is safe to swim or not. 

Bacteria is not the only water quality parameter we have noticed being negatively impacted this year. We have been receiving reports from our watermen of high numbers of dead crabs in crab pots at the mouth of our rivers. This is likely due to deadzone occurring in the mainstem of the Chesapeake Bay. The Virginia Institute of Marine Science is using computer models to accurately predict these conditions, and while the current dead zone is usually expected this time of year, it has expanded and become worse along the South, West, and Rhode. 

You can see in this image below that the West River in particular is 4mg/L worse right now compared to the long term average. This may explain why our local watermen have noticed an unusually high amount of dead crabs compared to previous years. 

Hypoxic or no oxygen/dead zone events occur in the bay because of excess nutrient pollution, specifically nitrogen and phosphorus. These nutrients, most commonly from fertilizers and sewage sources, cause excess growth of algae. When that algae dies, the decomposition process removes oxygen from the water- resulting in "dead zones." Fortunately, the VIMS model is forecasting an increasing trend in oxygen on our horizon, but we can not deny the significant impacts poor water quality has had on our waterways this year.