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

samples are collected weekly at 40 state-owned beaches from the week prior to memorial day through labor day.   water samples are taken at three locations along the beach and at three water depths (ankle-, knee- and waist-deep). the water from these locations is mixed to form one sample, which is placed in a new bottle and taken to a laboratory for analysis.

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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 Policy
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 Classification – Calculated Annually

State park beaches are classified into one of three categories based on their history of bacteria results in recent years: vulnerable, transitional, and less vulnerable.

Beaches are classified as “vulnerable” when the geometric mean standard of 126 Most Probable Number (MPN) / 100 ml is exceeded in three or more sampling seasons of the most recent five years of monitoring.

Beaches are classified as “transitional” when the geometric mean standard of 126 MPN / 100 ml is exceeded in two or fewer sampling seasons of the most recent five years of monitoring and was listed as “vulnerable” in the previous monitoring seasons.

Beaches are classified as “less vulnerable” when the geometric mean standard of 126 MPN / 100 ml is exceeded in two or fewer sampling seasons of the most recent five years of monitoring and was listed as “transitional” or “less vulnerable” in the previous monitoring seasons.

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