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Beach Monitoring: Safe to Swim?


When Does Monitoring Occur?

From approximately Memorial Day through Labor Day, the Iowa Department of Natural Resources conducts weekly monitoring of 39 state park beaches. 

What is Being Monitored? 

  • Microcystin (a toxin produced by harmful blue-green algae blooms), and
  • E.coli

About Swim Advisories

When microcystin or E.coli levels exceed certain standards/thresholds, DNR posts swim advisories telling beach-goers to stay out of the water due to health risks.

The Iowa Environmental Council tracks these weekly beach monitoring reports/swim advisories, as well as advisory trends from year-to-year. Click here to view our trend data.

Notable Statistics from Summer 2019:

  • Total number of E. coli advisories = 60
  • Total number of microcystin advisories = 21*
  • Honey Creek Resort Beach, Lake MacBride, and North Twin Lake East Beach experienced their first recorded advisories for microcystin since data collection began in 2006.
  • Of 37 weekly monitored beaches, 20 beaches recorded swim advisories this summer. 17 beaches did not record an advisory.
  • Backbone Beach was under advisory for E. coli for the first 13 weeks out of 15 weeks total.
  • McIntosh Woods Beach at Clear Lake was under advisory for E. coli the last 9 weeks of the summer out of 15 weeks total.
  • If Iowa adopted the EPA’s recommended advisory threshold for microcystin, which is 8 micrograms/L, an additional 14 advisories would have been issued for microcystin in 2019.

*Why did we change the number of annual microcystin advisories in 2019? 

The DNR issues swim advisories for microcystin at the beginning of the week if samples are greater than the 20 microgram/L advisory threshold. During Week 12 and Week 13 of 2019, DNR analyzed "endpoint" samples of beaches with microcystin advisories at the end of the week. As reported in emails from DNR dated Aug. 16 and Aug. 23, they found the endpoint sample was below 20 micrograms/L for three beaches that had been issued advisories. DNR made the decision not to include those advisories in the final count for the summer. We previously reported 24 advisories because those three advisories were issued by DNR during those weeks. We have now removed them from our final count in order to avoid confusion with what the DNR has reported. 

Weekly Water Watch

Every Friday during the summer IEC sends our Weekly Water Watch, an e-newsletter with beach updates and other important water news. Sign up to receive this e-newsletter.