The Fox River contributes more phosphorus to Lake Michigan than any other tributary. It’s also the second largest contributor of sediment. And while Wisconsin has strict rules to limit the amount of phosphorus flowing into its waterways, a new report shows that it hasn’t been enough to turn the tide on the problem in the Lower Fox River watershed.
Scientists from the U.S. Geological Survey monitored phosphorus and sediment levels in Lake Winnebago, near De Pere and at the mouth of the river from 1989 and 2021. The overall finding in the more-than-three-decade study: more work needs to be done, especially as climate change brings heavier rain events that wash more nutrients into the water.
So why is too much phosphorus a problem? Have phosphorus levels gone down in the Lower Fox River watershed? And what’s being done to fix it? Here’s what to know.
Phosphorus enters waterways from point and nonpoint sources
Phosphorus is an essential element needed for plants to grow. That’s why it’s a key ingredient in fertilizers on agriculture land. It is also present in manure, a natural fertilizer. Too much phosphorus, however, can pollute waterways and cause blue-green algae blooms when it’s washed into waterways during heavy rain events, which are becoming more common with climate change.