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The state of the river

The St. Croix has changed over time

Major changes have come to the St. Croix over the last 150 years. Researchers compared conditions at three important points in history:

  • 1850s-the effects of early farming and logging
  • 1940s-the beginning of drastic change
  • 1990s-the most recent data

Yesterday: 1800-1990

Americans moved into the St. Croix valley, and began logging the forests and clearing land for farms. Soil samples from the bottom of Lake St. Croix tell us that soil erosion increased in response to these changes. But because phosphorus-enriched fertilizers had not been invented, phosphorus levels in the river remained low.

Logging in the 1800s
Logging in the 1800s did not increase erosion very much, nor add phosphorus to the river. (Photo courtesy Minnesota Historical Society)

All that began to change in the 1940s. New fertilizers loaded the land with phosphorus. Expanding cities paved over large areas, increasing runoff. Soil erosion hit its peak in the 1950s and remains high.

Farm 1940s
Big changes started hitting the St. Croix in the 1940s, as farms began using phosphorus-based fertilizer. Industrial agriculture led to increased erosion. (Photo courtesy Minnesota Historical Society)
Development 1940s
The rapid growth of cities after World War II created a lot more paved areas, which altered the way water flows off the land and into the river. (Photo courtesy Minnesota Historical Society)

Today: 1990-2010

Phosphorus accumulation in Lake St. Croix is at an all-time high. Phosphorus, nitrogen and chlorophyll (a measure of algae in the water) are all above EPA recommended levels. The amount of surface-dwelling algae has increased sharply. Still, most users still find the river in excellent condition—meaning it's not too late to reverse these trends.

Tomorrow: 2010 and beyond

The St. Croix basin contains some of the fastest-growing counties in the region. By 2020, the population is expected to grow by 100,000. More people means more homes, more roads, more sewage-and more phosphorus entering the river.

Or does it? The people of Minnesota and Wisconsin can work with their elected officials to develop new ways to manage the St. Croix watershed. Improving the health of the river while also enhancing the St. Croix Valley as a place to live and work would benefit everyone. It would also offer insights to people everywhere who grapple with similar issues of reconciling economic growth with sustaining the quality of their environment.