KEYC - Minnesota River Sediment Having an Impact Over 150 Miles Downstr

Minnesota River Sediment Having an Impact Over 150 Miles Downstream

Minnesota River Sediment Having an Impact Over 150 Miles Downstream

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MANKATO, Minn. -

The United States Geological Survey was in Mankato monitoring the river today.

A problem in the Minnesota River is having an impact over 150 miles downstream in Lake Pepin.

A strange device hung precariously over the Veteran Memorial bridge in Mankato.

Its fins disappearing repeatedly beneath the murky water.

It's purpose...

Joel Groten of the United States Geological Survey says, "We are just measuring the sediment that is moving past this point when we come out and sample it."

Sediment such as rock, sand, and dirt flowing in the water.

Groten says, "From the first round of bedload sampling, this is what the bedload looked like today."

And this sediment is causing trouble nearly 150 miles downstream in Lake Pepin, southeast of Red Wing.

Groten says, "Basically, we are trying to answer how fast Lake Pepin is filling in."

Alan Forsberg, the Blue Earth County engineer, says, "If you look at the Minnesota River is down here...the prairie is up here about 200 feet. And that's because the last glacier and the waters released eroded this huge Minnesota River Valley."

"And so those rivers are very busy eroding themselves wider and deeper."

That erosion moves rock and sand into the Minnesota River, connecting to the Mississippi River, where it slowly flows downstream before settling in Lake Pepin along the Mississippi River, according to Groten.

Groten says, "They say that Lake Pepin might fill in within 100 years."

So to monitor this, the United States Geological Survey will be installing additional sensors along the river to monitor the river levels and sediment flow.

Groten says, "So we're going to have all these different sensors at different parts of the river. And one at the very end of Lake Pepin. So we're going to see all the sediment that's coming into Lake Pepin, and all that's leaving. And so we can see how much sediment [that's] getting trapped there. And hopefully the goal is to see how fast the lake is actually filling in in real time."

Upstream research, for downstream results.

Working similar to a sonar device, the automated monitors reports water depth and sediment amounts every 15 minutes.

The geological survey team comes 10 times a year to recalibrate these sensors.



--KEYC News 12