How do we reconcile good recreation with poor water quality?  How can we work together to improve water quality in the South Skunk River?  These are some questions I hope you will discuss with me at McFarland Park this Friday (Feb 9) at 5:30PM

The good: paddling!  The portion of the South Skunk River that flows through Story County* will be dedicated as a water trail this year.  Story County is lucky to have a river with so many acres of protected natural areas and with such well-marked public access points.  A lot of work over the years by a lot of dedicated conservationists has made that possible.

Skunk River Paddlers trip in 2015

The bad: water quality!  This stretch of the South Skunk is on the impaired waters list due to high levels of E.coli bacteria, an indicator for fecal contamination.

The ugly: rivers in the rest of the state aren’t any better. There are over 400 river/stream segments on the Iowa Impaired Waters List due to E coli.  That understates the problem—thanks to budget constraints, our state’s abundance of rivers, and a state law that limits what data can be used for regulatory determinations, 1040 river/stream segments weren’t assessed by the DNR at all.

Here’s a classroom analogy. Of the 426 stretches of river that sat the test in 2016, only 9 passed.  Under a proposed change to the scoring, 31 more could have passed, prompting misguided** concerns about grade inflation. The South Skunk River would have failed either method, but graded on a curve, it would have been in the cleaner half of the class.  Squaw Creek was not allowed to sit the test because of Iowa’s Credible Data Law, but would have scored in the dirtiest quartile.

As a paddler, I have to say that getting sick from something in the water is not a big safety concern for me—when I’m on the river I’m more concerned about strainers and low-head dams.  I don’t want to over-react to the water quality data and deny my kids the canoeing, fishing, and frog catching experiences that I enjoyed when I was growing up.  Based on the data I’ve seen, the E. coli levels in the South Skunk haven’t gotten worse since then.

Still, if you’ve heard from people who have gotten badly ill from a waterborne illness, you know it’s something to take seriously.  The milder cases are under-reported; who’s to say the stomach distress I attributed to a bad burrito wasn’t really a case of Campylobacter that I swallowed when I tipped my canoe.

Unfortunately, there doesn’t seem to be a good way to put those health risks into perspective.  The state standard of 126 E. coli colony forming units (CFU)/100mL is based on solid epidemiological studies of freshwater beaches, and corresponds to a defined level of risk: 36 people per 1000 swimmers will get a diarrhea after spending the day at the beach.  However, the experts I spoke to said you can’t extrapolate those water quality-illness relationships into truly dirty water.  Squaw Creek had a geometric mean almost ten times higher than the standard in 2016.  Does that mean that your risk of getting sick from swimming in it is ten times higher?  Definitely not.  Twice as high?  I have no idea.

If you want some good bedtime reading to understand why this stuff is so complicated, check out this EPA study on Quantitative Microbial Risk Assessment.  Here are some takeaway points.

  1. E. coli isn’t usually what makes you sick.  It’s an easy-to-measure proxy for other pathogens carried in contaminated water, like Cryptosporidium, Campylobacter, E. coli 157, and Salmonella.
  2. Whether you get sick depends on what kind of feces are in the water.  You are more likely to get sick from ingesting water contaminated by a human waste (i.e. a leaky septic system) than you are to get sick from water contaminated by cattle manure.  Swine manure is less dangerous than cattle manure, but there’s a lot more of it spread on the land. You are unlikely to get sick from poultry manure or geese droppings, since these animals are not as closely related to us.
  3. Whether you get sick depends on the dose you ingest—a child swimming is more likely to swallow water than an adult fishing.  You are more likely to swallow water while rolling your kayak than splashing yourself while canoeing.
  4. Whether you get sick depends on your body’s response to the pathogen.  Children, the elderly, and people with a compromised immune system may be at higher risk.

The good news is that it is possible to clean up water impaired by bacteria. Can we do it for the Skunk River?  Let’s talk about it!  Hope to see you on Friday.

*As Alan Spohnheimer proved in a recent talk, the Hamilton County portion of the South Skunk is also fun to canoe, you just have to be more adventuresome when it comes to access points and portages.

**All opinions expressed in this blog post are those of the author and do not reflect the views of Prairie Rivers of Iowa or its funders.  But seriously, if you consider how easy it is for a river to exceed the single sample limit (i.e. a raccoon in a culvert near the sample site), how long it takes for a river on the impaired list to get a TMDL completed, and how little power regulatory agencies have to control non-point sources of bacterial contamination, the DNR’s proposed change did not merit the outrage.

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