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Bone Lake Protection

Phosphorus

A lake's water quality refers to how free from contaminants it is and how well it can support its natural aquatic ecosystem.

What harms water quality?

Nutrients and Sediments
Nutrients such as phosphorus and nitrogen come from sediments (eroded soil), manure, pet wastes, improperly maintained septic systems, fertilizers, grass clippings, and leaves.

Phosphorus, whether from natural sources or commercial fertilizers, is plant food. After fertilizer is applied to a lawn, the excess nutrients are washed away by rains that flow to lakes and streams. Phosphorus causes excessive aquatic plant growth and algae blooms that turn the lake green.

Excess algae can reduce desirable bottom-rooted plants by blocking sunlight. When algae, plants, and other organic materials decay at the bottom of lakes this depletes oxygen in the water, making it difficult for fish and other aquatic life to survive. Reduced oxygen levels also contribute to winter fish kills in shallow lakes.

Most Wisconsin lawns and soils already contain adequate — and often excessive — amounts of phosphorus including soils in Polk County and around Bone Lake.

In Polk County, the sale and use of fertilizer containing phosphorus is prohibited in shoreland areas. If you use fertilizer 1000 feet from a lake or 300 feet from a river or stream the middle number of the formula (Phosphate) on the package must be 0.

Many municipalities have restricted the use of phosphorus for lawn fertilization and Minnesota has a statewide ban for residential properties. In Wisconsin, a statewide phosphorus ban of phosphorus for lawn fertilization was passed in 2009.

Do your part to protect Bone Lake from unnecessary nutrients, it is a good investment in your lakeshore property. Not only is clean, clear water more enjoyable for recreation, several studies, notably one on Lake Delevan Wisconsin and another on selected Maine lakes, have shown that good water quality and clarity is linked to higher property values.*

What can you do to protect Bone Lake's water quality?

Never allow lawn fertilizer, soil, leaves or grass clippings to wash into the water. Pick up pet waste, it contains nutrients and bacteria. Ashes from campfires contain high levels of phosphorus — keep them away from the water. Control storm runoff and soil erosion around your house by installing rain barrels, rain gardens or splash blocks. Maintain or restore a buffer of native vegetation along your shoreline. Inspect and maintain your septic system regularly.

Forty-four percent of the phosphorus entering Bone Lake comes from the watershed, the land surrounding the lake.
The graph below shows all the sources of phosphorus entering Bone Lake.

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*To read the Lake Delevan study visit www.wisconsinlakes.org/AboutLakes/DelavanStudy.htm.
The Maine lakes study can be found www.maine.gov/dep/blwq/doclake/research.htm.
Source: Wisconsin Association of Lakes, www.wisconsinlakes.org.