Iowa city lowers level of river to protect mussels
WATERLOO, Iowa — Just below the sand at the bottom of the Cedar River are thousands of natural water filters that improve water quality. Just one of them can filter more than 10 gallons of water per day.
They are freshwater mussels, the gem of the Midwest. And they’re considered the most endangered group of organisms in the United States.
“Mussels are really work horses. We have to protect and conserve them the best we can,” said Pam Wolter, founder and president of Cedar Valley Paddlers Club.
Using their gills, they filter water. However, the water must be relatively clean and clear for a mussel to survive. Too much sediment in the water will smother the mussel. They live on the gills and fins of fish for weeks or months, then are released to the river floor to live out their life filtering water and enjoying the nutrients that float by.
The Waterloo-Cedar Falls Courier reports that one of the main threats to Cedar Valley mussels was the drastic drop in water depth each year when the bladder dam, located just downstream from the Park Avenue bridge in Waterloo, was lowered as required by the Iowa Department of Natural Resources. During the overnight deflation, river levels were reduced about 4 feet in the sixmile stretch between Cedar Falls and Waterloo, causing mass stranding of freshwater mussels on the exposed river bottom. In their lifetime mussels don’t move very far, sometimes only a few feet, so a sudden drop in water levels leaves them stranded and eventually kills them.
At the request of the Iowa DNR and other advocacy groups, the city of Waterloo now lowers the dam about 2.5 inches per day over about a month period. Deflation this year began Monday and should be complete by Nov. 16.
“We appreciate the city of Waterloo’s cooperation as well as the many Cedar River users that may be impacted by this change in operations,” said Dan Kirby with the Iowa DNR.
The rubber bladders across the low-head dam became fully operational in 2012. They are inflated during summer months to raise metal gates, which boost the upstream river level by 4 feet to enhance boating and river recreation. The bladders can also be deflated during high water periods to avoid exacerbating flooding upstream.
In 2014, a longtime Cedar River fisherman, Dennis Wendel, alerted the local paddling community that thousands of mussels were dying on area sandbars. Wolter, a passionate environmentalist, heard the call and helped organize a mussel rescue the next fall. Wendell passed away in 2015, and the group became known as the Dennis Wendel Mussel Move project. They saved more than 1,000 mussels that year by moving them to deeper water.
With more than 40 volunteers, the Dennis Wendel Mussel Move project has saved thousands of mussels on the shores of the Cedar River since.
Flooding in 2016 left mussels safe, but in 2017 the group hosted its second rescue. In 2018 the city began slowly deflating the dam, and a leak in the structure in 2019 left the dam unused.
“We’re really excited that they did have to make changes because the water has been so low this year. We felt it was important to make sure the drop they have in the water is not going to cause problems with any of the mussels,” Wolter said.
In 2018, Wolter was inducted into the Iowa Volunteer Hall of Fame for her efforts toward improving her community.
She is thrilled to share that her group has discovered 15 mussel species in the Cedar River, when the amount previously recorded was five. They also found an endangered mussel, the Ellipse, and two rare black bandshell mussels that were pregnant. A biologist with the DNR left the project immediately and drove the bandshells to Minnesota where the DNR was restocking the threatened species.
The Iowa DNR, the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers began researching the disappearance of native freshwater mussels in Iowa 15 years ago. At one time about 54 species of native mussels were found in Iowa, and now there are about 42, according to the DNR. Nine of these are endangered. Another six are threatened and several more species are very hard to find.
There are thousands of types of mussels in the world, but the greatest diversity exist in North America with more than 300 on record after dozens have already gone extinct.
“They can really make water quality improve, but when it gets to the point there’s too much pollution or water sedimentation, it can kill them,” Wolter said.