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Beach Monitoring: Safe to Swim?

About Iowa beach monitoring

Clear Lake BeachFrom approximately Memorial Day weekend through Labor Day weekend each summer, water management agencies conduct monitoring for microcystin and E. coli bacteria at Iowa lakes. This is a 15- or 16-week period each summer. 

Since 2006, the Iowa Department of Natural Resources conducts weekly monitoring for 39 state park beaches (see full list below). 

The U.S. Army Corps of Engineers Rock Island District conducts weekly monitoring at Coralville, Saylorville, and Red Rock lakes. USACE Rock Island monitors its beaches according to the same protocols as Iowa DNR. 

When are swim advisories issued?

When microcystin exceeds an 8 microgram/L threshold or E.coli exceeds state standards, swim advisories are issued. Iowa DNR posts a sign at the beach to indicate an advisory and updates its beach monitoring website at www.iowadnr.gov/Things-to-Do/Beach-Monitoring. Prior to 2020, microcystin advisories were issued at a less protective 20 microgram/L threshold.  

The Iowa Environmental Council tracks these weekly beach monitoring reports and swim advisories each summer. The results of our tracking can be seen below.

Weekly Water Watch email

Weekly Water Watch

Every Friday during the summer recreation season, IEC sends Weekly Water Watch, an e-newsletter with beach advisory updates and other important water news.  

Trends in Swim Advisories

Microcystin-related Swim Advisories

Since the Iowa Department of Natural Resources beach monitoring program began in 2006, the number of annual swim advisories issued for microcystin has increased dramatically.  

Swim Advisories Microcystin 2006-2021

Cumulative Microcystin Advisories by Beach

E. coli-related Swim Advisories

Overall, the number of annual E. coli-related swim advisories issued at Iowa State Park beaches has trended downwards in the last six years. 

Swim Advisories E.coli 2006-2021

Cumulative E coli Advisories by Beach

Notable Statistics from Summer 2021

  • Total number of E. coli advisories = 88 
  • Total number of microcystin advisories = 23 (up from 12 in 2020)
  • Four beaches recorded advisories for both E.coli and microcystin
  • Of 38 DNR-monitored beaches, 24 total beaches recorded swim advisories this summer. 20 beaches did not record any advisory this year.
  • Backbone Beach was under advisory for E. coli for 11 weeks out of 15 weeks total in 2021 -  the lowest number it has seen since 2014, but still more than any other state park beach. Since 2014, Backbone has experienced the most E. coli advisories at 105.
  • Crandall’s Beach (Spirit Lake), Rock Creek Lake, and Springbrook Beach in Guthrie County experienced their first advisories for microcystin since 2015.