Trends in Swim Advisories
Number of Microcystin-Related Swim Advisories Issued at Iowa State Park Beaches
Microcystin-Related Advisories Issued Per Year
Since the Iowa Department of Natural Resources beach monitoring program began, the number of annual swim advisories issued for microcystin has increased dramatically.
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.
Number of E. coli-Related Swim Advisories Issued at Iowa State Park Beaches
E. coli-Related Advisories Issued Per Year
Overall, the number of annual E. coli-related swim advisories issued at Iowa State Park beaches has also trended downwards in the last six years.