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 
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?
Beach Monitoring

For up to date information, call the DNR Beach Monitoring Hotline:
(515) 725-3434

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

DNR Beach Policy

State Standard
The bacteria standard for Iowa’s recreational waters consists of two components.

  1. 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).
  2. A one-time maximum standard based on a single sample (235 colony forming units of E. coli bacteria per 100 mL of water).


Beach Classes
Beaches are placed on “vulnerable” list if they have violated the geomean standard 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 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 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.


Posting of Signs/Advisories
All beaches are posted with signs that provide general information regarding ways to reduce the 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.

Advisories are generally updated on Thursdays between Memorial Day and Labor Day, but may be earlier or later in the week depending on the timing of holidays, sampling schedules and availability of laboratory results.

Beaches that exceed Iowa’s geometric mean water quality standard for 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 signs that state, “Swimming is Not Recommended”.

Posting will only occur between Memorial Day and Labor Day. The advisory remains in effect until the geomean drops below the water quality standard.

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

Posting will only occur between Memorial and Labor Day. The advisory remains in effect until water quality samples taken from the beach drop below the one-time sample maximum.