2018 Impaired Waters List

The Iowa Department of Natural Resources is seeking public comment on the newly released draft impaired waters list.  Prairie Rivers of Iowa will be recommending that Squaw Creek and East Indian Creek be added to “Waters in Need of Further Investigation.”  We’ll also take this opportunity to try to demystify a topic that can be confusing, using examples from the South Skunk River watershed.

Every two years, the DNR is required to assess the available data to determine whether Iowa’s lakes, rivers, and wetlands are meeting their designated uses.  About half the rivers, and a bit more of the lakes have enough data to assess.  Since new waters are considered each cycle, the length of the impaired waters list doesn’t really tell us whether water quality is getting worse.  Since nutrients aren’t considered for most uses and the data used for the 2018 assessment is from 2014-2016, it doesn’t tell us whether the Iowa Nutrient Reduction Strategy is working.  What it tells us is the extent and severity of local water quality problems that have been officially vetted.

Recreational Uses

A river segment, lake, or reservoir that gets use by paddlers or where children play would be designated A1 (primary contact recreation use) or A3 (children’s recreational use).  To determine whether the water quality is good enough to support these uses, the DNR compares E. coli bacteria to the state standard (a geometric mean of 126 organisms per 100mL).  If the stream consistently exceeds the standard, that means there could be enough human or animal waste in the water to pose a health risk to anyone that swallowed some–a child splashing in the creek, or a paddler who tipped their canoe might get exposed to a waterborne illness.

Fully supporting:  None of the lakes or rivers in our watershed appeared on this list

Partially supporting: The South Skunk River above Ames was slightly impaired with high E. coli levels in one of three years.  Indian Creek near Maxwell, the upper part of Long Dick Creek in Hamilton County, Montgomery Creek in Boone County, Hickory Grove Lake in Story County, Lake Keomah and White Oak Lake in Mahaska County all have moderate E. coli problems.

Not supporting:  Prairie Creek in Boone County has consistently high E. coli levels.  The data was collected through an agreement between Iowa DNR and volunteers with the Squaw Creek Watershed Coalition.

Not assessed:  This includes Squaw Creek, East Indian Creek, McFarland Pond, and many others.

Wait a minute, Squaw Creek and East Indian Creek?  Didn’t we work with City of Ames and Story County Conservation to collect three years of monthly E. coli samples, starting during the assessment period?  Wasn’t the 2016 geometric mean ten times higher than the standard? Yes, but DNR never approved a quality assurance plan, so under Iowa’s Credible Data Law, they can’t use our data.  However, we will write to DNR to recommend that they add those streams to Iowa’s list of waters in need of further investigation (WINOFI).  We’re aware that bacteria cleanup plans for large rivers are difficult to do and are a low priority for the department, but we want people to be more aware of the health risks.

Aquatic Life Uses

The South Skunk River is  a warm water stream with a smallmouth bass fishery, so is designated B(WW-1).  Most of its perennial tributaries don’t have enough water or habitat for gamefish so are designated* B(WW-2) for other aquatic life.  Fish kill reports, biological monitoring of fish and invertebrates, and monitoring of dissolved oxygen and some toxic chemicals are used to assess whether water quality is good enough to support these uses.

*Adding to the confusion, smaller creeks are given a presumptive A1 B(WW-1) designation until a Use Attainability Assessment proves otherwise.  This change supposedly gives them extra protection, but I don’t see how that would work in practice.

Fully supporting: A lower segment of the South Skunk River in Mahaska County, Little Wall Lake, Hickory Grove Lake, lower Squaw Creek, and Montgomery Creek appear to have good enough water quality for a healthy aquatic community.  FYI: Fish aren’t bothered by high nitrate or E. coli.

Partially supporting:  The South Skunk River above Amesthe upper part of Squaw Creek, Long Dick Creek, upper Ballard Creek, and Walnut Creek are on the impaired waters list due to fish kills or a low quality fish or invertebrate community.

Waters in Need of Further Investigation:  Onion Creek, Worrell Creek, and College Creek had some low scores for fish or invertebrates, but DNR hasn’t worked out an appropriate threshold for these headwater creeks.  The lower part of Ballard Creek was removed from the impaired waters list and placed in this category when DNR discovered an error in the previous assessment.

Not Assessed: This includes several segments of the South Skunk River, Dye Creek, Clear Creek, Keigley Branch, West Indian Creek and many others.

Takeway message:

If a river was added to the impaired waters list, don’t assume it’s gotten dirtier.  Maybe it was always polluted and we hadn’t bothered to look.  And by the same token, if a river is not on the impaired waters list, don’t assume it’s clean.