The WildsideWater that runs off the land around here finds its way through Lake Pepin on the Mississippi River. The big lake to our south was formed by sand conveyed into the Mississippi River valley by the steeper Chippewa River, forming a delta that acts like a dam.
Water that runs off the land around here finds its way through Lake Pepin on the Mississippi River. The big lake to our south was formed by sand conveyed into the Mississippi River valley by the steeper Chippewa River, forming a delta that acts like a dam.
the end of the last ice age, Lake Pepin extended up to near Prescott. Sediment carried in from the Mississippi and Minnesota Rivers has filled in the lake and river valley over time. Now the head of the lake is south of Red Wing, Minnesota.
Lake Pepin today is about 22 miles long. The lake varies between a mile and two and a half miles wide and covers about 40 square miles. The lake is very shallow at the upstream end and is about 40 feet deep near the downstream end.
Lake Pepin and the Mississippi River served Native Americans as a transportation artery for thousands of years. The French explorer Father Louis Hennepin first traversed the lake by canoe in 1680. Hundreds of steamboats carried immigrants into our area up the Mississippi River and through the lake. Billions of board feet of pine logs and lumber from the Minnesota and Wisconsin forests floated downstream through Lake Pepin.
Lake Pepin is legendary for the sublime beauty of the limestone bluffs along both shores. Legend has it that a Dakota woman named Winona leapt to her death from the bluff at Maiden Rock. The lake is also legendary for its fierce winds and waves. In 1890 the Sea Wing ferry capsized in a storm, killing 98 people.
The lake has its own legendary monster. Pepie, perhaps a cousin to Nessie of Loch Ness in Scotland, was first sighted near Lake City, Minnesota in 1871.
The real monsters on Lake Pepin are the towboats and barges. The long-term average date for the first towboat up the lake through the ice is March 20. The lake is mostly free of ice and towboats should be traveling up the lake any day now.
Pepie the Lake Pepin monster is an advocate, a “spokesmonster” for clean water with a Facebook site. Other real monsters in Lake Pepin are sediment and the phosphorus carried with it.
Research scientists from the Minnesota Science Museum’s St. Croix Watershed Research Station sampled cores of sediment from Lake Pepin and analyzed the sediment accumulation rate and phosphorus content. They discovered that the lake is filling with sediment at a rate 10 times the natural rate before European settlement and phosphorus is accumulating 15 times the natural rate. Since 1830, Lake Pepin has lost 17 percent of its volume. At the current rate of sediment loading, the lake is projected to be filled in 340 years. The large amount of sediment and phosphorus loading to the lake has resulted in highly eutrophic conditions with dense summer blooms of blue-green algae.
The St. Croix Watershed Research Station, Minnesota Pollution Control Agency, the Metropolitan Council, the Minnesota and Wisconsin DNRs, the University of Minnesota , the U.S. Geological Survey and the U.S. Army Corps of Engineers have conducted extensive studies of the lake and its sources of sediment and phosphorus loading. On average, the St. Croix River contributes 25 percent of the flow, four percent of the phosphorus and almost no sediment. The Upper Mississippi River contributes 50 percent of the flow, 26 percent of the phosphorus and little sediment. The Minnesota River contributes 27 percent of the flow, 32 percent of the phosphorus and 75 percent of the sediment flowing into Lake Pepin. The Twin Cities wastewater treatment plants contribute 24 percent of the phosphorus.
It will take concerted effort and large investments in watershed and water quality management to clean up Lake Pepin. That work is already underway in both Minnesota and Wisconsin. Slaying the sediment and phosphorus monsters in Lake Pepin will extend the life of the legendary lake and clear up the water for us and for Pepie.
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