One July evening four years ago, seven inches of rain fell in less than 12 hours on the Willow River in eastern Minnesota. The tributary swelled, like many others across the region.
“A swath of 8 to 10 inches of rain extended from northern Crow Wing County, MN through Aitkin and Pine counties then across northern Wisconsin from Danbury to Hurley,” the National Weather Service reported.
The Willow joins the Kettle River in the town named Willow River. Following the flood, the Kettle rose 12 feet.
An 80-year-old dam on the Willow could not handle the raging torrent and was irreparably damaged. A popular flowage created by the dam was drained, degrading a state forest campground and previously lakefront homes.
The sheriff ordered a voluntary evacuation of the town of Willow River due to concerns about the dam giving way catastrophically. But the water dropped slowly until the lake bed was exposed.
Last month, workers began replacing the damaged dam to bring the water back up — also solving a problem caused by the previous dam.
The new structure won’t be another vertical wall, but will let water cascade down the drop over a rocky slope. It will provide fish habitat and passage where they were before blocked. It should also be more resilient in future floods.
“I’m highly in favor of replacing the old Willow River dam with a rock rapid\weir construction,” said commenter Rick Lent during a public input phase of the project. “This is a once in a lifetime chance to improve fish movement and safety.”
The new rapids also won’t pose a drowning hazard like the previous dam. In July 2011, a 46-year-old man visiting from Missouri drowned when he was swept over the dam during high water as he tried to save his brother from drowning. The brother survived.
From wall to weirs
Workers began the project by diverting the Willow River around the dam so they could safely remove the structure. They then filled in the eroded channel below the dam and began placing rock weirs.
“As a home owner on Stanton Lake, I would like to see the rock rapids dam constructed,” wrote Jen Bonrud in earlier comments on the proposal.
Stanton, the 86-acre flowage held by the dam, has several private properties, as well as a state forest campground. Since the dam was damaged in 2016, the lake has been empty.
The work should be finished this next spring, and the lake behind it will start to fill as the snow melts.
“I am a long-time user of the Willow River area and the Kettle River, both paddling, fishing and camping,” wrote Saben De Smet. “With both friends and family that live on the Kettle and the Willow reservoir, the dam missing has greatly changed their homes, shore lines, and their usage of the water. I am 100% behind the fish ladder idea as it will keep spawning grounds open to all species.”
The $1.8 million project was funded by the state of Minnesota through the 2017 bonding bill passed by the legislature.
At least 200 billion gallons of water fell on eastern Minnesota and northwest Wisconsin during the July 2016 storm. The focused area and short time it fell in is a hallmark of extreme storms that will increase with global warming.
According to NASA, whose scientists have put people on the Moon, and sent remote-controlled rovers to Mars, climate change will cause more such “extreme precipitation events.” Or as the state of Minnesota’s chief climate science agency calls them, “Historic Mega-Rain Events.”
It’s not possible to link any one storm to global warming, and researchers are still learning the complexities of Earth’s atmosphere. But it’s simply a law of physics that warmer air holds more water.
“Within the scientific community it’s a relatively well-accepted fact that as global temperatures increase, extreme precipitation will very likely increase as well,” said Joao Teixeira, co-director of the Center for Climate Sciences at NASA’s Jet Propulsion Laboratory. “Beyond that, we’re still learning.”
Analyzing the number of “Mega-Rain Events” in Minnesota since 1973, state climate scientists say there has been a “sharp uptick” since 2000, when temperatures began to rise more rapidly in response to fossil fuels discharging carbon into the atmosphere.[T]he 21 years from 2000-2020 had almost two times as many mega-rains as the 27 years spanning 1973-99,” the state climatology office reports.
The Willow River dam project is an example of how costly climate change could be in terms of natural resources and taxpayer dollars. As of an announcement this week, there will be no coal-burning power plants in Minnesota by 2035.
- Willow River Dam Restoration Project – Minnesota DNR
- July 11, 2016 Flash Flooding – National Weather Service
- Central Minnesota Flood: July 11-12, 2016 – Minnesota State Climatologist