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summer day at the beach in Iowa
Water Quality Monitoring

Routine water quality monitoring is conducted at all of the State Park beaches and many locally managed beaches in Iowa. In order to help protect the health of those wishing to recreate at the beaches, the Iowa Department of Natural Resources works with various public health and management agencies throughout the state to inform the public of the most current water quality conditions.

Outdoor recreation at beaches in Iowa is typically limited to the time period between Memorial Day and Labor Day. Therefore, most beach monitoring is conducted and standard swimming advisories are issued during this time frame. Results for specific beaches are published as soon as they become available.

Coralville Reservoir, Red Rock and Saylorville Beach Monitoring Results

For information regarding beach advisories and conditions, please contact the Natural Resource Specialist or Park Ranger at the following lakes:

  • Saylorville Lake - (515) 276-4656 
  • Lake Red Rock - (641) 828-7522 
  • Coralville Lake - (319) 338-3543 

Beach Monitoring Update - May 20, 2020

Use of 8µg/L Microcystin Advisory Value for the Beach Monitoring Program

Brief History: Iowa has used the World Health Organization (WHO) microcystin value of 20 ug/L for beach advisories since 2006. On December 19, 2016 EPA published the “Human Health Recreational Ambient Water Quality Criteria and/or Swimming Advisories for Microcystins and Cylindrospermopsin” in the Federal Register for public comment. The recommended criterion for microcystin was proposed at 4 ug/l and indicated that states could use the value as a water quality standard, a swimming advisory value, or not use it at all.

On March 8, 2017, the DNR, IDPH, and IDALS collaborated on a review of the proposal and sent formal comments to EPA for consideration. The comments supported the effort to provide guidance on algal toxins, but highlighted concerns regarding the scientific approach used to generate the proposed advisory values.

EPA finalized the criteria in May 2019 and revised the microcystin advisory value to 8 ug/l based on public comments. Iowa did not utilize this advisory value last season due to timing, but state agencies did commit to a thorough review to determine if 8 ug/l microcystin would be utilized for the 2020 beach season.


Based on DNR and IDPH review of the adjusted final numbers and EPA’s responses to public comment, the state has decided to move forward for the 2020 beach season utilizing EPA’s microcystin advisory value of 8 ug/l.

Clarifying points:

  • This determination is specific to the use of the microcystin advisory value of 8 ug/L for beach advisory purposes only.
  • It is possible the microcystin advisory value may change in the future based on updated information applied to EPA's calculation method, or based on new epidemiological studies that focus on dermal, gastrointestinal, and/or respiratory impacts.
  • Use of EPA's microcystin advisory value of 8 ug/L will result in more advisories compared to the WHO value of 20 ug/L. More advisories do not necessarily mean water quality has changed significantly in a given waterbody.
Water Monitoring FAQ
+ Why monitor beaches?
+ What is the DNR monitoring?
+ Can these bacteria make me sick?
+ Why doesn't the DNR monitor pathogens?
+ What are the sources of bacteria and pathogens?
+ How are the samples collected at the beach?
+ What levels are considered safe?
+ What factors cause high levels of bacteria?
+ Potential illnesses associated with swimming?
+ How can I avoid getting sick?
+ Eating fish from waters with high levels?
More information about cyanotoxins
Beach Monitoring

For current beach advisory, call the DNR Beach Monitoring Hotline: (515) 725-3434

The DNR Beach Monitoring Website and Hotline are updated on Fridays during the monitoring season.

If you have any questions or concerns, contact us by email.

DNR Beach Monitoring and Advisory Implementation Plan
State Standard

The bacteria standard for Iowa’s recreational waters consists of two components:

  • A geometric mean standard based on 5 samples in a 30-day period (126 colony-forming units of E. coli bacteria per 100 mL of water).
  • A one-time maximum standard based on a single sample (235 colony forming units of E. coli bacteria per 100 mL of water).

State advisory threshold for Cyanobacteria Toxins (Blue-Green Algae Toxins)

The Iowa Department of Natural Resources, in partnership with the Iowa Department of Public Health (DPH), follows guidelines recommended by the US EPA in 2019 for monitoring cyanotoxins in recreational waters in order to safeguard public health.

  • 8 µg/L total microcystins from any composite beach sample.
Posting of Signs/Advisories

All State monitored beaches are posted with Information Signs on indicator bacteria and blue-green algae toxins that provide general information regarding ways to reduce the potential health risk associated with swimming at public beaches. These signs will also inform the public of current monitoring efforts and ways to obtain the data.

Posting will only occur between Memorial Day and Labor Day (recreational monitoring season). Advisories are generally updated on Fridays of each week during the recreational monitoring season, but may be earlier or later in the week depending on the timing of holidays, sampling schedules and availability of laboratory results. All monitored beaches will be signed to “Watch / General Information” when an advisory is not in effect or when monitoring is not occurring.

Beaches that exceed Iowa’s geometric mean water quality standard for indicator bacteria (the geometric mean of 5 samples in a 30-day period exceeds 126 colony forming units of E. coli bacteria per 100 ml of water) will be posted with a warning sign that state, “Swimming is Not Recommended”.

Vulnerable and Transitional Beaches that exceed the one-time sample maximum water quality standard for indicator bacteria (235 CFU/100ml) will be posted with a warning sign that states,“Swimming is Not Recommended”.

Beaches that exceed Iowa’s advisory threshold level for cyanobacteria toxins (8 µg/L total microcystins) will be posted with a warning sign that state, “Swimming is Not Recommended”.

Advisories will remain in effect until the geomean for indicator bacteria drops below the water quality standard, the one-time sample maximum for indicator bacteria drops below the water quality standard, and the one-time sample maximum for Cyanobacteria toxins drops below the advisory threshold.

Beach Classes

Beaches are placed on “vulnerable” list if they have exceeded the geomean standard for indicator bacteria two or more times in the previous five years. The list is reviewed annually to update the beaches classified as “vulnerable”.

Beaches are placed on the “transitional” list if improvements have been observed with respect to indicator bacteria levels. Beaches in the transitional classification will be eligible to be reclassified to “non-vulnerable” if they do not exceed the geometric mean standard for one year.

Beaches that have not exceeded the geometric mean indicator bacteria standard or only exceeded the standard once during the most recent five years are classified as being “less vulnerable” to experiencing prolonged or chronic problems with elevated levels of indicator bacteria.

Swimming Registration at State Parks

People wishing to swim outside the designated swimming beach areas at Iowa state parks, for example to train for a triathlon, must obtain special permission by completing a registration form and communicating with local park staff.

For information and guidelines:
Swimming Registration Form