Polluted Runoff

Agricultural runoff transports sediments, fertilizers, and other chemicals into lakes.

Urban runoff washes salt, oil, and other pollutants into storm drains and into our lakes. Construction site runoff washes sediments into lakes.

What is Runoff?

Runoff is excess water that comes from hard surfaces like roof tops, driveways, parking areas, patios, and compacted soils. Runoff water washes fertilizer, eroded soil, car fluids, and other pollutants into the lake. Polluted runoff can come from both agricultural and urban sources, and is serious and continual problem for our lakes.

As the amount of hard surfaces increase within a watershed (often because of low density development), there is less green space for water to soak into the ground, and polluted runoff problems increase. Reducing the amount of wetlands within the watershed and replacing natural shorelines with traditional manicured lawns increases polluted runoff problems (wetlands and shorelands act as natural pollutant filters).

Impacts polluted runoff has on our lakes

Some of the negative effects polluted runoff has on lakes include excess nutrients (such as phosphorus) which:

• Cause algae blooms. Excess algae can block sunlight, deplete oxygen in the water, and contribute to fish kills.
• Cause excessive aquatic plant growth, which can impact recreational opportunities and increase lake management costs for local groups.

A sediment plume clouds this lake.

• Causing the water to become cloudy, or “turbid,” and covering plant leaves which reduces the amount of sunlight reaching plants. Cloudy water also affects fish by damaging gills and impacting their ability to find food.
• Burying fish spawning areas and other valuable aquatic habitats.
• Picking up and transporting additional pollutants such as metal flakes, debris, and toxics into our lakes.

What you can do to reduce polluted runoff

Property owners can help reduce the amount of polluted runoff:

• Get a soil test before applying lawn fertilizer. Your soil may have plenty of nutrients (especially phosphorus) already.
• Never allow lawn fertilizer, soil, or grass clippings to wash into the lake.
• Pick up pet waste (full of nutrients that can cause algal blooms and potentially harmful bacteria) promptly.
• Reduce the amount of impervious surfaces (areas where water cannot soak into the ground) on your shoreland lot.
• Let water soak into the ground (restoring shorelines and building rain gardens are popular methods) before it reaches the lake.
• Maintain or restore a buffer of native vegetation along your shoreline.
• Control soil erosion around your house.
• Inspect and maintain your septic system regularly.

Learn more about shoreland restoration