Lake Pepin

(St. Croix Watershed Research Station: Science Museum of Minnesota, 2010)

(St. Croix Watershed Research Station: Science Museum of Minnesota, 2010)

In Minnesota, nearly half of the state – about 50,000 square miles – drains to Lake Pepin, along with small parts of South Dakota, Iowa, and Wisconsin. This water drains from farm fields and parking lots, and from all different types of land. Between the 1930s and 1960s, the amount of sediment flowing into the South Metro Mississippi River and Lake Pepin more than doubled, from 300,000 to 700,000 metric tons per year, coinciding with a period when wetland drainage was widespread and the mechanization of agricultural production was on the rise. Currently, about one million tons of sediment  enters and settles in Lake Pepin annually. Research has demonstrated that the increased rate of sedimentation is directly proportional to the increase in flow, or the volume and force of water coming from the surrounding rivers, streams, and ditch systems: the higher the flow, the higher the sedimentation rate.

Maiden Rock, Lake Pepin 1862, as painted by Robert Scott Duncanson

Maiden Rock, Lake Pepin 1862, as painted by Robert Scott Duncanson

Lake Pepin, created by the delta of the Chippewa River, at one time extended to current day St. Paul.  Natural rates of sedimentation have been slowly filling Lake Pepin since the end of the last glacial period, approximately 12,000 years ago. Lake Pepin currently extends from Red Wing, Minnesota downstream 22 miles to Reads Landing, covering 26,000 acres. With an average width of 1.7 miles, Lake Pepin is the widest stretch of the entire Mississippi River. Extensive research has been conducted on the sedimentation occurring in Lake Pepin, as rates have increased 10-fold in the last 150 years.

Source: National Oceanic and Atmospheric Administration

National Oceanic and Atmospheric Administration

As the Mississippi River flows from its headwaters in Itasca, Minnesota through the river-lake Pepin, it continues to collect water from all or parts of 31 states and two Canadian provinces, and roughly resembles a funnel which has its spout at the Gulf of Mexico. Waters from as far east as New York and as far west as Montana contribute to flows in the lower river. The pollutants carried in the waters of the Mississippi and its tributaries (covering 41% of the contiguous United States) have created a large “dead” zone in the Gulf of Mexico, which varies in size each year depending on the concentrations of nutrients being discharged. Excess nutrients in water bodies create algal blooms which deplete oxygen levels to the point that no aquatic life can survive. The National Oceanic and Atmospheric Administration (NOAA) estimates that the dead zone costs U.S. seafood and tourism industries $82 million a year. The Gulf’s seafood industry accounts for more than 40 percent of the nation’s seafood. As is the case with sediment, nutrient concentrations are also proportional to flow rates. The greater the volume and force of the water, the greater the sediment and nutrient loads, and ultimately the greater the impact on both Lake Pepin and the Gulf of Mexico.

Efforts are underway in Minnesota to adopt site-specific water quality standards for the stretch of the river from St. Paul to Lake Pepin, as well as implementation plans to achieve those standards. The nature of the pollutants threatening Lake Pepin are complex and require careful, cooperative, and strategic attention. The large drainage area crosses state boundaries and is overlaid with a wide range of interests not limited to agriculture and commercial navigation.  The Lake Pepin Legacy Alliance is determined to preserve and restore Lake Pepin as an integral part of the Upper Mississippi River System by elevating the importance of implementation of the recommendations and “best practices” that science and reason dictate. Leading with the tools of education and information we will protect the natural heritage of Lake Pepin.

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