High capacity wells may impact brook trout
By Ben Rodgers
The effects of modern irrigation practices on local fish won’t be known for some time.
But experts have one species from the area that is worth keeping an eye on.
High capacity wells use large amounts of groundwater to irrigate fields, especially in this area of the state.
That same groundwater feeds streams and is vital to the brook trout.
“The reason that brook trout are able to exist in the middle of Wisconsin is because of the groundwater infiltration,” said Dan Isermann, U.S. Geological Survey employee and leader of the Wisconsin Cooperative Fishery Research Unit at University of Wisconsin-Stevens Point. “In terms of temperature it (groundwater) keeps the water temperature in a range they can tolerate.”
The popular game fish also finds the water temperature in groundwater-fed streams like the Tomorrow River and Little Plover River ideal for spawning.
“Brook trout often spawn in areas where infiltration is occurring or at least in areas with high-dissolved oxygen,” Isermann said. “Their eggs are sensitive to low-dissolved oxygen and warm water. Areas of groundwater infiltration offer the right range of temperatures. It keeps the water cool enough for the eggs to survive.”
Brook trout in Wisconsin are native to the Central Sands, the Driftless Area and Lake Superior tributaries.
Other varieties, including rainbow and brown trout have been introduced into the Central Sands and are more resilient when it comes to water temperature.
While groundwater does feed into lakes, gauging the impact on fish populations there is more difficult.
Fish like largemouth bass and bluegill are very adaptable to temperature differences. Also lakes have dozens of factors when it comes to fish die off, including size, depth, location, vegetation, source and oxygen levels.
Because of this the brook trout, which is only found in streams, makes a great signal species for study.
But Isermann said researchers are currently at a disadvantage when it comes to finding a correlation between high capacity wells and fish populations.
“We can generalize what we know about how fish react to changes in water level, but to try and link that with what’s going on with the high capacity wells is difficult,” he said. “We’re in the middle of it. They’re already drawing groundwater out of our refuges, so to speak. We lost the ability to do before and after because we’re after already.”
One person who has some data on the rivers is George Kraft, director of the Center for Watershed Science and Education at the UW-Stevens Point and the UW Extension Service.
Kraft has data that currently shows a 10 to 25 percent depletion in the streamflow in the mainstream headwaters of the Tomorrow River.
“We predict pretty severe future impacts to the Tomorrow and its tributaries if irrigation continues to expand the way it has been,” Kraft said.
His data on the Little Plover River shows an even higher depletion flow pumping rate of 40 percent for much of the river. The recent wet weather also masks any long-term changes.
“During these flush times you may not worry a whole lot about the pumping impact,” Kraft said. “But in average times or dry times, you may have these problems develop.”
A reduced flow can spell trouble for the brook trout in a few different ways, according to Matt Salchert, president of the Frank Hornberg Chapter of Trout Unlimited in Portage County.
Less water means the water currently in the streams will get warmer faster. Less water also means fewer natural habitats, like tunnels or holes for the native species.
During dry years there are parts of the Little Plover River can be crossed bare foot without getting wet. That may have changed with all of the recent rain, but the river has dropped so significantly over the past few years that conservation efforts may be for naught.
“It really doesn’t pay for us to do stream work on that stream because if the river dries up what’s the point of having a structure for the fish to go under?” Salchert said.
As president of a conservation group Salchert understands the argument from both sides.
“My thing is I like to eat. I grew up on a farm. I realize in life with any decision we make there’s always going to be something affected by it,” he said. “There’s no such thing as a pretty lunch.”
Salchert also recognizes the importance of agriculture to Wisconsin.
“We can’t shut down a growing operation completely just because we need some trout to survive,” he said. “I don’t think that’s a viable option. A lot of people might argue with me, but what are we going to do? Americans need to eat and someone is going to take the water somewhere.”
The growth in high capacity wells from the 1960s to present day could have an impact on the fish that has been around for much longer.
The combination of cold groundwater and the right water levels over centuries has turned the brook trout into a highly sought after catch for anglers with enough skill and patience.
With generation after generation of brook trout in the area, the fish tends to get smarter, fight harder and be more tenacious than brown or rainbow trout which were introduced into the area.
“Even though they aren’t as big, the Holy Grail of fishing for me is catching a nice size brook trout in its home environment,” Salchert said.
At the same time he knows that if agricultural irrigation trends continue to grow, it could very well spell the eventual end of the fish in this part of the state.
“The brook trout are the canary in the coal mine,” Salchert said. “They are the indicator we need to look at. If we are losing these fish we need to look at why and find out the reason.”
The Wisconsin Department of Natural Resources declined to comment for this story.
“Due to the fact that new court filings were made late last week regarding our authority in the area of approving high cap well applications, we will respectfully decline interviews at this time because the subject is a matter of ongoing litigation,” said Andrew Savagian, section chief for the office of communication for the DNR, in an email dated June 19.