Drought means low flow to iconic North Shore waterfalls, trouble for fish
Much of Minnesota is experiencing moderate to extreme drought conditions. It’s having a big impact on agriculture, water wells, lake recreation and on the iconic waterfalls and fish of the North Shore.
The water levels on the rivers and streams there are very low for this time of year.
The lack of rain is largely to blame. These water bodies are fed mostly by runoff — snowmelt and rainfall within their specific watersheds, said Cheri Zepplin, a Department of Natural Resources regional information officer.
“Many North Shore streams and rivers have very little groundwater feeding them, so during times of low precipitation there is little runoff feeding into the rivers,” Zepplin said.
Some visitors may be disappointed when they see these once booming waterfalls down to a trickle, but it can allow for a unique experience.
“The waterfalls are low flow right now, but that in itself can be interesting,” Zeppelin said. “It provides a different perspective and a reminder of how our watersheds function. Nature is resilient and the waterfalls will come back.”
For the fish living in those North Shore streams and rivers, it’s bad news.
At a glance:
Low flow means less habitat and fewer places to hide from predators and heat.
High heat means lower dissolved oxygen levels in the water, making it harder for fish to breathe.
Low water levels can cut off access to ideal spawning habitats.
To escape the heat, young fish may migrate into lakes too early.
Stress can make it difficult for fish to put on growth.
As flow levels drop, habitats shrink.
“With this level of drought, you’ll get intermittent areas where you may end up with water flowing only subsurface,” said Duluth fisheries supervisor Deserae Hendrickson. That results in isolated pools where fish can become trapped, unable to escape predators or the heat.
Finding cooler areas is essential because when the water gets warmer it can’t hold as much dissolved oxygen, making it difficult for fish to breathe.
The low flow presents a unique problem for anadromous species — fish that migrate along the streams and rivers to reproduce. On the North Shore, that includes several species of trout as well as some salmon.
These fish will lay their eggs upstream, and some species’ young will spend the first year or two of their lives in the rivers and streams.
“We definitely saw a lot of younger fish that should not really have been migrating out yet,” Hendrickson said. “When they feel like it's just getting too hot, often they try and escape that by migrating downstream into the lake. But if they do that too early, their survival is very minimal.”
Plus, when fish are stressed, they can’t effectively process their food in a way that helps them put on growth, Hendrickson said.
And if drought conditions continue into fall, some species may not be able to reach their ideal spawning habitats. It could have lasting impacts on the population.
“I would expect that fish that hatched out this spring, they're probably not doing great. You know, they’re a lot more fragile when they're smaller,” Hendrickson said. “But if we also get a second-year class that fails because fish weren't able to get to some spawning habitat, that's going to be a bigger impact that may be a bit more longer lasting, it could take a couple years to recover population levels.”
It could mean trouble this winter, too. If water levels stay low, it’s possible streams could freeze all the way to the bottom. Snow that falls on initial ice formations can help insulate streams from the cold, so getting precipitation will be important in the winter as well.
"I mean, certainly, this is one of the effects of climate change, you know, anticipating less regular rainfall and larger, intermittent rain events that are spread further apart that tend to create more challenging conditions for loss of fish and wildlife both,” Hendrickson said. “So those are going to be things I think that we will be dealing with for a long time. I hope not. But that seems to be the way we're trending.”
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