How clean is the water in Iowa's beaches? You can find out before you swim

If your holiday weekend plans include taking a dip at one of Iowa's swimming beaches, make sure to check its water quality first. Swimming is currently not recommended at six of Iowa's beaches and two more are closed due to maintenance.

How can you check up on water monitoring, beach classifications and know what locations are open or closed? Iowa Department of Natural Resources tracks it all and updates the public weekly.

How does Iowa swimming beach monitoring work?

The DNR collects weekly samples at 39 state-owned swimming beaches to determine the public's risk of coming in contact with waterborne diseases. Testing starts a week prior to Memorial Day and runs through Labor Day. 

Water samples are taken at three spots along the beach and at three different depths, ankle-, knee- and waist-deep.

The water from these locations is then mixed to form one sample, which is placed in a new bottle and taken to a laboratory for analysis, according to the DNR's website.

What causes contamination at Iowa's beaches?

Fecal contamination of beach water can happen due to improperly constructed and operated septic systems, according to DNR officials, as well as sewage treatment plants, manure spills, storm water runoff from lands with wildlife and pet droppings, or direct contamination from waterfowl, livestock or small children in the water.

Rain is one of the biggest factors in generating high levels of bacteria in Iowa, according to the DNR. Runoff from heavy showers can lead to high levels of fecal bacteria and contaminate water at beaches. Rain also increases sediment in the water, making it murky, which helps bacteria survive. 

Are Iowans at risk by swimming at state lakes?

Thousands of people swim at Iowa's 39 beaches yearly and most of them don't get sick.

"The group is E. coli that we are looking at, and within that group there are ones that are pathogenic, which can harm us, and there's a large group of ones that are not," said Dan Kendall, Lake and Beach Monitoring Coordinator for DNR.

However, children, the elderly and people with weakened immune systems have an increased risk of becoming sick when in contact with contaminated water, according to the DNR.

One of the most common symptoms a person can develop swimming in contaminated water is diarrhea. Skin, ear and respiratory infections are also possible.

How does the Iowa DNR determine what level of bacteria at Iowa beaches is safe?

DNR officials follow the United States Environmental Protection Agency;s guidelines to determine if bodies of water are safe for recreation depending on the amount of bacteria. 

The bacteria level in the water is "acceptable" if the geometric mean is not greater than 126 colony-forming units per 100 milliliters of water for E. coli bacteria, according to EPA guidelines.

How does the Iowa DNR classify swimming conditions?

DNR lists data on whether swimming conditions are OK at 39 of its state park beaches and many locally managed beaches. Beaches are classified on a color-coded map at IowaDNR.gov. Data is updated each Friday.

"It's there to help people decide if they want to recreate or not," Kendall said.

Current conditions are listed as:

• OK for swimming: (Designated by a green dot)
• Swimming not recommended: (Designated by a yellow dot). DNR officials will post this advisory if the beach exceeds Iowa's geometric mean water quality standard for E. coli; is a "vulnerable" or "transitional" beach that exceeds a one-time sample maximum water quality standard for bacteria; and/or has exceeded the EPA's threshold for Blue-Green Algae Toxins.
• Beach closed: (Designated by a red dot)
• Insufficient data: (Designated by a blue dot)
• Special status: (Designated by a purple dot)

While DNR will post signage promoting swimming can be unsafe, this does not mean you are prevented from swimming at the beach.

"This gets down to risk, and what people will accept for risk," Kendall said, reiterating that it's up to individuals themselves whether they'll take the risk of getting sick. For individuals with compromised immune systems, it may be a larger risk than for others.

DNR officials classify state park beaches into one of three categories annually based on their history of bacteria results in recent years:

• Vulnerable: Beaches are considered vulnerable when the geometric mean standard is exceeded in three or more of the five most recent sampling seasons.
• Transitional: The beach's geometric mean standard is exceeded in two or fewer sampling seasons of the five most recent years of monitoring and was listed as “vulnerable” in the past monitoring seasons.
• Less vulnerable: The beach's geometric mean standard is exceeded in two or fewer sampling seasons of the five most recent years of monitoring and was listed as “transitional” or “less vulnerable” in past monitoring seasons.

'Swimming not recommended' at these Iowa beaches

• McInstosh Woods Beach
  • Beach classification: Vulnerable
  • Last sample result: June 21
• Marble Beach
  • Beach classification: Less vulnerable
  • Last sample result: June 21
• Denison Beach
  • Beach classification: Vulnerable
  • Last sample result: June 20
• Pine Lake State Park
  • Beach classification: Vulnerable
  • Last sample result: June 21
• Prairie Rose State Park
  • Beach classification: Vulnerable
  • Last sample result: June 19
• Lake Darling Beach
  • Beach classification: Vulnerable
  • Last sample result: June 21

Which Iowa beaches are currently closed?

• Geode Lake Beach
  • Monitoring has been suspended for the 2023 season due to renovation activities
• Lake Ahquabi Beach
  • Monitoring has been suspended temporarily due to renovation activities