Wisconsin’s Phosphorus Rule is Approved

In December, 2010 Wisconsin became the first state in the country to adopt phosphorus water quality standards for lakes, reservoirs, rivers, and streams.  The Environmental Protection Agency has approved Wisconsin’s revised rule as a revision to Wisconsin’s federally-approved National Pollutant Discharge Elimination System program under the Clean Water Act.

Under the new rules DNR determines the phosphorus discharge limits based on the condition and quality of a watershed.  Limits can vary depending on whether a waterway is already impaired by phosphorus, among other factors.

Already this summer, many Wisconsin lakes are experiencing algae blooms and excessive aquatic plant growth, both of which are fueled by phosphorus pollution.  The excess nutrients increase the populations of algae, which can multiply in waterways particularly when the water is warm and the weather is calm. 

Algae is typically not harmful to humans, however, some species produce toxins which can affect people by causing illness so swimming and other water activities should be avoided in areas where algal is present.  Blue-green algae blooms have been blamed for the deaths of many dogs which are more vulnerable because they often drink the contaminated water or swallow the algae as they clean their coats. 

Almost 175 Wisconsin waters are officially listed as “impaired” due to excessive phosphorus levels.  The new rules will help clean up those lakes and protect the others.  The new rule is in addition to a smaller effort from 2009 which restricted the sale of fertilizers containing phosphorus and banned the sale of dishwasher detergents with phosphorus.

A Success Story - Lake Minnewawa Weed Harvesting

In the 1970’s, Lake Minnewawa was so choked with weeds that residents could no longer enjoy the lake.  Boating was impossible and water clarity and phosphorous levels were awful.  A group of concerned residents decided they needed to do something to save the lake and on December 15, 1977 as association was formed calling itself Save Minnewawa Association.

In 1982 the association purchased their first weed harvester and trailer, which was replaced in 1994 by a larger, but used 1987 Aquarius Systems 620 harvester, that is still in use today.  The association does not receive state funds to run the harvester; it is financed by membership, business, and other local group donations along with fund raisers.  The work required to run the machine is immense and there are a lot of donated hours by board members and volunteers to keep the equipment running.

Three months out of the year the harvester runs five days a week about 8 hours a day (weather permitting) to maintain the 4,500 acre lake.  Not all of the lake gets cut either, there are designated no cut areas established by the DNR and certain native plants aren’t cut like lily pads, wild rice, and bulrush.  Since the harvester has been in use not only has the amount of weeds decreased, but water clarity has significantly increased as well.

A big reason for this is because there are fewer weeds dying in the lake and decomposing to the bottom.  If the vegetation is left to rot, the nutrients in it that have been absorbed from the water are released back to the water column and become nutrients for the next weed growth or algae bloom. But something far worse occurs; as the vegetation decays, it uses up the oxygen at the bottom which affects fish as well as native plants.  The weeds contain a huge amount of phosphorous which is being removed along with the weeds, the more phosphorous in a lake, the more algae growth, therefore the lower water clarity.

Some people in the area don’t believe in the weed harvester and feel that cutting the weeds leads to more growth, but Steve Olson, LMA board member disagrees.  “If that were the case, then they would have never needed to harvest here in the first place.”  Other people have suggested controlling the weeds with chemicals instead of the harvester, but the cost is very prohibitive with a price tag of half a million dollars compared to the $25,000 a year it takes to run and maintain the weed harvester.

With the aid of the Aquarius Systems weed harvester and 18 years of sufficient lake improvements, Save Minnewawa Association officially changed their name in 1995 to Lake Minnewawa Association (LMA).