Swimming not recommended at 13 Iowa state beaches this week due to E. coli levels

More than a dozen Iowa state beaches have posted swim warnings this week due to high E. coli levels found in the water.

Iowa Department of Natural Resources spokeswoman Tammie Krausman said none of the beaches with the E. coli warning are technically closed.

“We don't generally don’t close the beach for swimming in case people want to go picnicking or other things,” Krausman said. “We always say we provide (Iowans) with the information, and they can make the decision.”

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The DNR tests water at about 40 the state beaches weekly. For single samples, if the E. coli levels exceed 235 organisms per 100 milliliters of water, the DNR issues a “swimming not recommended” warning and posts signs.

The second criteria is geometric mean, which is the median level of E. coli in five samples in a 30-day period. If it surpasses 126 organisms per 100 milliliters, a swimming warning is posted.

The DNR this week flagged 13 state beaches that surpassed either the single sample threshold, the geometric mean sample threshold, or both, for E. coli:

Water samples from the beach at Backbone State Park showed E. coli levels are exceptionally high. The DNR reports the single sample from Backbone had 24,000 organisms per 100 milliliters of water — well above the limit of 235 — and the geometric mean was 1,091 organisms per 100 milliliters.

A similar E. coli concentration was detected at Crandall’s Beach at Spirit Lake in 2022. At the time, the DNR reported the E. coli level exceeded the upper limit of the agency’s tests. That contamination was thought to be caused by a large algae bloom and recent rains that had likely washed bacteria into Spirit Lake.

This week’s water tests also showed Lake Ahquabi State Park’s beach had very high levels of E. coli: 16,000 organisms per 100 milliliters of water in a single sample, and a geometric mean of 1,097 organisms per 100 milliliters, when the limit for geometric mean is 126 organisms.

Union Grove Beach in Tama County also tested high for E. coli with 3,300 organisms per 100 milliliters of water in the single sample, and a geometric mean of 2,530 organisms per 100 milliliters.

E. coli in recreational waterways can be dangerous because it can indicate fecal contamination, which can potentially expose swimmers and other users of the water to pathogens that can cause illness.

Sources of bacteria in Iowa lakes include geese that lounge on the sand, manure runoff from farm fields and septic tank discharges.

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An ongoing issue

When the DNR started its weekly beach water testing in mid-May, four beaches surpassed the E. coli threshold and had swim advisories. This included Backbone, Beeds, Black Hawk and Nine Eagles beaches.

High E. coli levels have been an issue at Iowa’s beaches for years. Last year, Iowa had the highest number of swimming advisories for bacteria at state beaches in more than a decade, possibly because of abundant rainfall that washed fecal material into Iowa’s lakes.

Over the course of 15 weeks of testing in 2024, the DNR issued 145 swimming advisories, including 130 for bacteria, seven for toxins and eight for both.

A Gazette and Investigate Midwest investigation in 2022 showed a fifth of water monitoring tests administered on Iowa lakes between 2002 and 2022 exceeded the state’s threshold of 126 units of bacteria per 100 milliliters of water.

If Iowans choose to recreate near the beaches with posted warnings, Krausman said they should take some precautions.

“If you want to run your dog, wade, or do things like that (with) minimal recreational contact, just be extra careful,” she said. “Be sure you wash up and shower and make sure you wash your hands before consuming anything.”

Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues. She is also a contributing writer for the Ag and Water Desk, an independent journalism collaborative focusing on the Mississippi River Basin.

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Comments: olivia.cohen@thegazette.com