By Howard Meyerson
July 2012 was a hot month for fishing on Lower Peninsula rivers, but state fish managers and Consumers Energy officials say a new upwelling system behind Tippy Dam should help cool downstream Manistee River waters and perhaps even boost trout and steelhead growth.
“It will help,” said Mark Tonello, a fish habitat biologist with the Michigan Department of Natural Resources. “The problem is the impoundment which makes the waters downstream unnaturally warm. A number of springs come into the river and we do stock trout there, but those waters are borderline.
“We get a lot of natural reproduction on the gravel, but the majority doesn’t survive the summer temperatures.”
The upwelling installation, essentially submerged bubblers that push cold bottom water to the surface where it cools water spilling over the dam, was installed in late July. It is the last of four to be installed by the utility which committed $1.75 million to address fisheries concerns at its Au Sable, Manistee and Muskegon river hydro projects in a 1992 settlement agreement approved by the Federal Energy Regulatory Commission when Consumers applied to relicense the dams.
The Tippy project uses four submerged diffusers. It is expected to lower water temperatures by one to two degrees. Three of the diffusers sit at 28 feet in waters just upstream from each of the three turbines. A fourth sits at the bottom of a 46 foot pool, 600 feet upstream of the dam.
“That one will bring cold water up into the stream. The river flow will bring that closer to the dam. And the closer diffusers will bring the water up and put it into the inlet,” said Dave McIntosh, the river-hydro licensing engineer for Consumers Energy.
The technology being used had to be custom fabricated for each of the dams which includes the Au Sable River Mio Dam, Muskegon River Croton Dam and Manistee River Hodenpyl Dam. Mio and Croton were completed in 2010. Hodenpyl was installed in 2007.
Each installation was designed to for the unique water flow at each site. They are triggered and activated when the river water reaches temperatures between 68 and 72 degrees. The diffusers are performing well, but the outcomes are somewhat varied, according to McIntosh. Each system is designed to run differently depending on the volume of cold water that is available behind each dam.
State officials monitoring progress on the projects said positive results have been seen at Hodenpyl and good results are expected at Tippy. However, the jury is still out for Croton and Mio.
“Croton is a mixed bag. It is still being evaluated,” said Kyle Kruger, the DNR’s hydro-licensing coordinator. “We are not seeing as much benefit initially as we hoped to see. We are seeing some, but the changes are more subtle than an instantaneous degree or two.
“At Mio it’s harder to tell. That system runs 24 hours a day and the concept there is to make the cold water move down the main channel with the warm water sitting on top.”
Evaluations are underway for both of those facilities, according to Kruger. But the Hodenpyl project delivered a 2.5 degree Fahrenheit change.
“It’s exceeding our computer modeling expectations,” Kruger said. “Hopefully that will be the case at Tippy. “We’ve been pretty pleased with what we see at Hodenpyl.
Tonello said the temperature drops recorded at Hodenpyl will not “make or break the situation. On a really hot summer we are going to lose some fish, but any amount of cold water we get there will help.”
© 2012 Howard Meyerson