Lake Life Today: Phosphorus -- Why is Your Lake at Risk?

Phosphorus is a naturally occurring nutrient that creates lake algae. A rapid increase or accumulation of too much phosphorus can cause a lake to be out of balance, creating massive algae blooms that turn lake water green from the algae’s pigments, smells terrible, degrades wildlife habitat, and can potentially harm human and pet health.

Phosphorus comes from lots of sources – pet waste, fertilizers, household cleaners, motor oil – none of which should ever find their way into a lake. But the biggest source of phosphorus is soil and sediment that is washed into a lake after a severe rain event. We know, due to climate change, that the rain events we are now experiencing are more intense. Severe storms cause phosphorous loading during the first hour of such events. This is called the “first flush.” Watch out for the “brownish” stormwater because it is laden with the nutrients, especially phosphorus.

Signs of erosion on your property show you that phosphorus in stormwater can take a direct path to your lake. Look around for stormwater channeling, or even more intense “gullying” left behind after a big storm, especially near buildings and parking areas where stormwater “sheet flows” off impervious surfaces and cascades its way to the waterbody.

Added together, even small sources of pollutants – a little stormwater runoff, a little pet waste on the lawn, a minor application of fertilizer – can all add up to create a much bigger problem for your lake. A little pollution from you, your neighbor and others around the lake, year after year, can put your lake at huge risk!

What can you do? For a more complete list of those things you can do to help promote and protect your lake’s water quality, see information on Lake Friendly Yard Maintenance at Vermont’s Department of Environmental Conservation (Watershed Management Division).