A New Group Aims to Save a Vanishing Lake

By Reggie McLeod

The big difference between a river and a lake is current. In the 22-mile stretch of Lake Pepin the Mississippi River widens out and behaves more like a lake than a river. The current slows to a snail’s pace, which creates a big settling basin of sorts, where silt and sand carried by the faster river currents gets a chance to fall to the lake bottom and stay there. As a result, the river below Lake Pepin is cleaner and clearer than it is above the lake. It’s a geological fact of life that the lake is filling in, but it’s filling in much faster than it would naturally, thanks largely to soil erosion from agricultural fields on the Minnesota River watershed.

The TMDL (total maximum daily load) process mandated by the federal Clean Water Act required states to create plans for cleaning up “impaired waters.” Lake Pepin is on the impaired list for high levels of sediment and phosphorus in the water. Norman Senjem, who works in the Rochester office of the Minnesota Pollution Control Agency (MPCA), has been working on the TMDL plan for Lake Pepin.

About 10 times as much sediment and 15 times as much phosphorus now flows into Lake Pepin as did before settlement of the region in the mid 1800s. The Minnesota River, he explained, contributes about 75 percent of the sediment and half of the phosphorus in Lake Pepin.

Sediment is filling in the lake, as well as many of the backwater and sloughs in the rest of the Upper Mississippi River. Phosphorus, which enters the river from excess fertilizer and wastewater treatment plants, triggers plant and algae growth in the lake, especially during very dry spells,when the river’s flow slows to the point that it takes 11 or more days for water to get from the upper end of the lake to the lower end.

Nitrogen, which also enters the river from the same sources, has much the same effect, though phosphorus is the limiting factor in Lake Pepin. Nitrogen in the Mississippi is the main cause of the “Dead Zone” in the Gulf of Mexico.

Senjem confessed that cleaning up the sediment and phosphorus in Lake Pepin will be difficult, because most of it is probably getting into the river from “nonpoint” sources, rather than from “point” sources, which usually refers to a pipe pouring something into the river. The nonpoint sources are probably mainly agricultural fields from which soil and fertilizer are washed into ditches, creeks and rivers.

The Minnesota River joins the Mississippi in the Twin Cities after flowing through south-central Minnesota. Minnesota has already banned phosphorus in lawn fertilizer. More than 600 wastewater treatment plants operate in the Lake Pepin watershed. Most, especially the largest, have dramatically reduced their phosphorus discharge in recent decades, but the plan needs to anticipate the effects of the Twin Cities growing by a million people in the future.

Mike McKay, whose home is in Wacouta, Minn., on the upper end of Lake Pepin, used to be able to easily boat across to Bay City, Wis. It has become a difficult trip, even on a jetski, which can travel in very shallow water.

“All summer long we watch boats getting stuck,” he said.

Last August he and five neighbors got together to discuss the problem.

“Can something be done, or will it just become a navigation ditch?” they asked. “Let’s determine if there’s something that can be done.”

McKay took on the task of researching the problem. He said he “was absolutely blown away” by the volume of information that had been collected by agencies monitoring the river. He was also impressed by the willingness of people in the departments of natural resources, Army Corps of Engineers, MPCA and other agencies to help him.

When he reported back to his neighbors, they decided that Lake Pepin needed a group of citizens from Minnesota and Wisconsin to advocate for a cleaner lake, so they started the Lake Pepin Legacy Alliance.

The first meeting of the alliance, on May 18, 2009, in Red Wing, Minn., drew hundreds. The group now has more than 200 members and is growing, McKay said.

Perhaps the quickest way to clean up the lake would be to get farmers to follow the rules already on the books, especially requirements in Minnesota that restrict farming within 50 feet of the high-water level of creeks, rivers, lakes or wetlands, according to McKay.

In most rural areas, a casual drive in the country will quickly reveal that these setback requirements are often ignored. The alliance is working to spread the word to farmers and public officials about the setback rules. Their next step will be pushing for better implementation.

“There is enough information to know what works,” McKay said. “Implementation is the key.”

The draft TMDL plan will be presented at a public meeting scheduled for Sept. 22, from 2 to 6 p.m. at the St. James Hotel, in Red Wing.

July-August 2009 / Big River Magazine