Current Water Quality in Story County (updated May 26)

Nitrate

Nitrate (a form of nitrogen) is a concern for the dead zone in the Gulf of Mexico. Prairie Rivers of Iowa and our partners have worked to promote practices in the Ioway Creek watershed that would reduce nitrogen and phosphorus loss. Before commercial fertilizers were introduced, nitrate levels in Iowa streams would have been less than 3 mg/L. While not relevant here, 10 mg/L is the drinking water standard.

 Current nitrate levels in Ioway Creek, from a sensor in the Iowa Water Quality Information System:

Nitrate in Ioway Creek has remained above 10 mg/L since April 22.

nitrate graph

Current nitrate levels in Walnut Creek, near Kelley. This site is influenced by several nearby drainage tiles, which provide a pathway for nitrogen to escape from crop fields. Nitrate has stayed above 20 mg/L for most of May.

 Water levels in rivers

To avoid dragging your canoe when paddling the South Skunk River, you’ll need at least 90-110 cfs at the USGS gage north of Ames.

At 1600 cfs, you need whitewater gear, as shown below  On April 23, the South Skunk rose 3 feet following a 2 inch rain, but a few adventurous kayakers were braving the rapids.

The Skunk River Paddlers had a leasurely trip from Ames to Cambridge on April 2nd, when the gage at S. 16th St measured 350 cfs.

Volunteers cleaned up trash in Ioway Creek while paddling on May 21, when the gage at Lincoln Way was around 140 cfs.

South Skunk at W Riverside Road / near Ames USGS Water-data graph for site 05470000, South Skunk near Ames, IA

whitewater kayakers in the South Skunk River

Fecal bacteria

E. coli bacteria is an indicator of fecal contamination. Not everyone who goes swimming or boating will swallow water, and not everyone who swallows water will get sick if there is human or animal waste in the water, but when E. coli is high, there is a greater risk.  Water quality may have changed since the last sample, so take greater precautions if it has rained recently and the water is murky.

  … in Rivers

Rivers and streams in central Iowa frequently have E. coli levels above the state standard.  When enjoying paddling or fishing take some extra precautions to avoid accidentally getting river water in your mouth or on food.  We monitor 15 streams in Story County for nutrients and fecal bacteria, but keep in mind conditions change quickly and we can only monitor monthly.  Avoid going in the water during and immediately after rain–we have measured E. coli levels as high as 100,000 colonies per 100mL in Ioway Creek during storm events.

Recreation standards apply from March 15 to November 15.  On May 18, 2022 (following rain), thirteen of fifteen sites exceeded the primary contact standard and five sites exceeded the secondary contact recreation standard.  Enjoy the new rapids on the South Skunk River at River Valley Park–this site usually meets the standard.

 … in Lakes

Iowa DNR and local partners monitor public swimming beaches on weekly basis from Memorial Day to Labor Day, with results posted here.   Here are results from the 2021 monitoring season.

The primary contact recreation standard is 235 colonies per 100mL for a single sample.  During the 2021 season, 2/15 samples at Peterson Park beach and 3/15 samples at Hickory Grove Lake beach exceeded this threshold.  For evaluating the entire season, the standard is a geometric mean of less than 126 colonies/100mL.  Both beaches were within the standard, with geometric mean of 58 colonies/100mL at Hickory Grove Lake and 17 colonies/100mL at Peterson Park. 

Hickory Grove Lake is on the Impaired Waters List due to high E. coli levels and excessive algae growth in previous years but there has been extensive work to improve water quality.  The lake levels were too low for the beach to be usable in 2021.

kids at beach
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