Low levels in Minnesota rivers affecting water quality

Low Mississippi River
High temperatures and a lack of rain has cut the flow of the the Mississippi River south of St. Cloud. Stagnant pools and debris fill areas that are usually covered with water this time of year.
MPR Photo/Tim Post

The Snake River in east central Minnesota is crystal clear as it flows through a wooded area just north of the town of Mora. Only speckled mid-morning sunlight makes it through the low hanging tree branches to the water below, but that's enough to illuminate the sandy river bottom.

Bill Dilks, coordinator for the Snake River Watershed, stands on a bank, several feet above the river.

Bill Dilks
Bill Dilks is coordinator of the Snake River Watershed Board. The Snake River's flow has dwindled because of a lack of rain and warm summer temperatures.
MPR Photo/Tim Post

"You can see the bottom and you can see it's only six inches deep. This time of year normally it would be way above your knees if you were to wade across it. Now, I've got hiking boots on, I don't know it would be much over the top of my boots," Dilks said.

This is Mora's Canoe Park, a place that hasn't seen many paddlers lately.

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"It would be a great exercise," joked Dilks. "I would say to get some really water-proof boots. Because you're going to be portaging most of the way and dragging it over the rocks, and dragging it through the woods where you normally wouldn't be."

While most of Minnesota is in a dry spell, this part of the state has been hit especially hard. Dilks says they haven't seen any significant rain for about two months.

That means the level of the Snake River, which is a major tributary for the St. Croix River, is way down.

The Snake River
The Snake River is unusually low for this time of year. A lack of rain and steamy summer temperatures means the river is down by several feet.
MPR Photo/Tim Post

In the language of a hydrologist, the river's flow should be around 400 cubic feet per second. Dilks says daily measurements right now put it somewhere between 60 and 70 cubic feet per second.

"If you start getting lower than that, then you compound the impacts on that whole life cycle that you find in the river," Dilks said.

That life cycle includes everything from microorganisms to the lake sturgeon that sometimes find their way into this river. And the harm low river levels do to aquatic life has other water watchers concerned too.

In the state Department of Natural Resources office here in Cambridge, hydrologist Mike Mueller prints out a map of the state's watersheds. Watersheds with low levels in lakes, rivers and streams are in red. Mueller says the splotch of red that started in east central Minnesota recently, is spreading to other parts of the state.

"The whole North Shore, much of the north central part of the state has all been added to that very dry, very low flow conditions in streams and tributaries," Mueller said.

For Mueller, low water levels means trouble for the region's fish population. Algae thrives in those conditions and when a thick mat of algae starts to decompose, it lowers dissolved oxygen levels in the water. Mueller also says when water levels are down, rivers and lakes heat up faster, sending the lowest members of the food chain into deeper, cooler water. That means fish have to work harder to find a meal.

Mike Mueller
Mike Mueller is a hydrologist with the Minnesota Department of Natural Resources. Mueller says water levels in some parts of Minnesota are approaching the low point they hit in 1988, when a drought hit the region.
MPR Photo/Tim Post

"The adults can probably find sanctuaries because they're stronger swimmers and they're able to move into deeper holes and find some refuge. But the young ones may not be able to do that."

Hydrologist Mike Mueller hasn't seen water levels this low since 1988. That's the year Minnesota suffered through a drought. Soaring summer temperatures and little rain sent lake and river levels to record lows. A DNR report found it hard to determine just how many fish died that summer but the report said populations of less mobile aquatic species, like mussels, were likely hit hard.

The only antidote to low water levels is, obviously, rain. Climatologists say while the hot, dry weather pattern is expected to stick around for awhile, there's a chance a cooler, wetter trend could begin this weekend.