Half of state park beaches had warnings this summer

More than half of Iowa's state park beaches had at least one week this summer when state officials warned against swimming there because of bacteria or toxins from blue-green algae.

Lake Darling in Brighton was toward the top of the list with 10 weeks of advisories against swimming.

The Iowa Department of Natural Resources reported 118 swim advisories at the 39 state park beaches after conducting weekly tests from Memorial Day weekend through Labor Day. This is up from 79 advisories in 2019 and 111 in 2018.

E. coli bacteria, which indicate feces in the water, caused 112 advisories in 2020. Elevated levels of microcystins, which can cause gastroenteritis, allergic responses and potentially life-threatening liver damage, caused 12 advisories. Together this is more than 118 because in six tests Iowa beaches had both too much E. coli and microcystin.

Twenty of 39 beaches had at least one advisory, with six state park beaches having 'no swim” notices at least half the summer.

Lake Darling, where the Iowa DNR completed a $16 million restoration project in 2014, has had microcystin and bacteria warnings each of the last two summers.

Michelle Balmer, with the department's Lake Restoration Program, said much of Lake Darling's watershed is privately owned and most is used for agriculture.

'We've seen some changes in the watershed, including an increased number of animal feeding operations,” she said.

'We can't control the whole watershed - I wish we could - but we have to respect that individual landowners have to make those decisions on their own. Conservation on the landscape at large has to be continually worked on.”

Balmer said the DNR is considering other ways to reduce E. coli advisories at Lake Darling, including routing water drainage around the beach or changing the slope of the beach to keep the sand dry. Wet sand is a better environment for bacteria growth.

Lake Darling had 10 weeks when E.coli bacteria closed the lake for swimming. During two of those weeks the lake saw elevated levels of microcystins.

Backbone State Park, a Dundee park that celebrated its 100th year of operation this year, had the most weeks with advisories at 14 of 16 this season. McIntosh Woods in Ventura had 11 weeks of advisories. Lake Darling and Denison Beach each had 10 weeks with warnings against swimming.

It's not always easy to determine why some Iowa lakes have spikes in pollution, said Dan Kendall, an environmental specialist in charge of the Iowa DNR's beach monitoring program.

Heavy rain can wash manure and other contaminants from nearby fields into lakes or streams. Much of Iowa had drought conditions this summer, which might be why western Iowa's Green Valley State Park, which perennially has had microcystin warnings, had no advisories in 2020, Kendall said.

'There are many factors that can play into why cyanobacteria blooms occur including weather, temperature, nutrient availability, and other environmental stressors,” he said.

Some lakes with longer-term water quality problems have gotten more study. The U.S. Environmental Protection Agency recently approved three lakes - McIntosh Woods; Nine Eagles Lake, in Davis City; and Hickory Grove Lake, in Colo - for plans to reduce E. coli bacteria.

Early study has shown the sandy beach area is harboring much of the bacteria, often from manure from geese or other animals, said Jeff Berckes, water quality improvement plan program coordinator.

'The next piece is to create a program around this to clean it up,” Berckes said.

A second round of study would include Lake Macbride, in Solon, among other lakes.