Phosphorus fuels Algae Growth – Lake Petenwell Phosphorus Reductions Under Way

Phosphorus has long been recognized as the controlling factor in plant and algae growth in Wisconsin lakes and streams.  In small doses, phosphorus (P) is a good thing. It’s necessary for organisms to grow, which is why farmers apply it to their crops and homeowners apply it to their gardens. But in large doses, it can cause problems for the exact same reason. Large amounts of phosphorus can cause too much plant and bacteria growth, which can have drastic consequences. Excessive phosphorus is responsible for the noxious blue-green algae blooms that appear on Wisconsin lakes in the summer, reducing property values, causing fish kills and diminishing quality of life on the lakes for humans and wildlife alike.

There are two types of phosphorus pollution: Point source pollution and nonpoint source pollution. Point source pollution has a specific origin, such as a discharge pipe at a factory or outfall of a waste water treatment plant. Nonpoint source pollution, meanwhile, has a much broader area of origin or no specific source at all. Nonpoint source pollution can come from cropland, grazing pastures, lawns, parks or any other area where phosphorus is applied, whether as fertilizer or as organic waste. The excess phosphorus washes away with rain or snow melt and makes its way into adjacent bodies of water. Because nonpoint source pollution is by nature an aggregate of pollution from several origins, it is more difficult to monitor and control than point source pollution.

In December 2010, the DNR established standards for phosphorus levels in different types of water bodies, whether from point or nonpoint sources. A month later, new performance standards took effect for farmers requiring them to curb phosphorus potentially coming off their fields.  These standards establish how much phosphorus can be in a body of water and set rules for those limits to be incorporated into municipal and industrial waste water permits  to reduce the negative effects on water ways, such as contributing to blue-green algae growth. Information about the specific standards is in the Phosphorus Management and Regulation in Wisconsin

These standards affect facilities that are direct dischargers of phosphorus, which are required by their permits to meet assigned limits on phosphorus levels in their discharge. Lower standards for phosphorus in a water body result in stricter limits on the amount of phosphorus that a point source may discharge into that water body. Traditionally, to achieve these limits, point sources would upgrade their facilities or alter their operations to reduce the amount of phosphorus in the facility’s discharge.

However, the prevalence of phosphorus pollution in Wisconsin’s waters would make it difficult for point sources to achieve required water quality standards through facility upgrades alone. According to an economic impact study performed by the DNR, the costs of facility upgrades for state point sources to meet phosphorus standards could total approximately $1-2 billion.1 Additionally, facility upgrades do not directly address the issue of nonpoint phosphorus pollution.

As one strategy to lessen the overall cost of meeting stricter discharge limits, the phosphorus rule includes a provision called the adaptive management option (AMO), which is a watershed-level strategy that focuses on reducing phosphorus pollution from both point and nonpoint sources. In the long run, this option may reduce more total phosphorus and save money for point sources compared to traditional point-source phosphorus controls.

Looking at the local level, the Annual Phosphorus Load Input (see chart) on Lake Petenwell has been substantially declining and is more than 50% lower in 2011 than in 2000.  With the recent regulations we expect to see these numbers continuing their decline.  In addition to reducing the phosphorus input level through regulation, several other initiatives have been implemented and or completed recently to help reduce phosphorus levels and maintain healthy algae growth limits.  Click HERE to review a substantial list of those initiatives.

How you can reduce your phosphorus output:

Regulatory agencies like the Wisconsin Departments of Natural Resources and Agriculture, Trade, and Consumer Protection are working with communities around the state to reduce stormwater runoff, and to encourage agricultural practices that reduce soil erosion while maintaining high crop yields. Locally, landowners and interested citizens can help minimize the problems associated with algal blooms by working together with partners in their watershed to reduce the amount of nutrients that reach nearby lakes, streams, and ponds. You can help reduce nutrient concentrations by promoting the following practices in your community:

  • Use lawn fertilizers only where truly needed
  • Prevent yard debris (e.g., leaves, grass clippings, etc.) from washing into storm drains
  • Support local ordinances that require silt curtains for residential and commercial construction sites
  • Plant and maintain vegetative buffer strips along shorelines of lakes, ponds and streams. Note: Native plants are much more effective at filtering runoff than the typical grass species found on residential lawns.