You may have heard the term “impervious surfaces” in some of our other articles, but what are they exactly? This week’s blog article explains impervious surfaces, how they impact water quality, and what we can do to minimize them to keep our lakes clean and healthy.
Impervious surfaces are hard surfaces that increase runoff when it rains. Impervious surfaces include roofs, paved driveways or walkways, and solid patios. Large areas of impervious surfaces can create fast-flowing rivers of runoff during heavy rains. This quickly flowing water picks up pollutants and sediments along the way and deposits the pollutants in the lake. This can cause big problems for the water and the creatures that depend on it.
How Impervious Surfaces Impact Lakes
When it rains, water hits impervious surfaces and flows towards streams and lakes. It is not absorbed into the ground like it would with grass or soil. Instead, it rushes across these surfaces, picking up all sorts of pollutants along the way. Pollutants such as fertilizers, pesticides, oil and gas, animal waste, and soil itself can be washed into the lake. These pollutants end up in lakes, where they can cause issues like algal blooms, cloudy water, and can even harm people, fish, and other wildlife.
Eutrophication: The Algae Overload
One big problem caused by impervious surfaces is eutrophication. This happens when lakes get too many nutrients, like nitrogen and phosphorus, from things like fertilizer and waste. Algae in the water gobble up these nutrients and grow like crazy, forming thick, green layers that block sunlight and use up oxygen. This makes it hard for other plants and animals in the lake to survive.
Sedimentation: Muddy Waters
Impervious surfaces also lead to more dirt and sediment getting washed into lakes because of the high flow volume of entraining sediment. This makes the water cloudy and murky, which isn't just unpleasant for swimming—it can also smother plants and animals that live on the lake bottom, disrupting the entire ecosystem.
Hidden Dangers of Chemical Contamination
The hard surfaces of roads and driveways collect all sorts of chemicals from cars, like oil and gasoline, as well as pesticides and fertilizers from lawns. When it rains, these chemicals get washed into the lake, where they can harm fish, birds, and other animals, as well as make the water unsafe for us to swim in or drink.
Ways you can reduce the impact of impervious surfaces
- Limit the size of impervious surfaces such as sidewalks, driveways and patios on your property to allow rain to soak into the ground and not runoff.
- Minimize lawn areas by planting shrubs, ground covers and trees that can slow the rate of water runoff better than grass. Lawn areas recharge groundwater less efficiently than planted landscaped areas.
- Direct rainwater runoff from gutter drains to areas that are landscaped. This provides the plants with the moisture that is needed for survival and increases groundwater recharge.
- Sweep driveways and walkways instead of hosing them down.
- Encourage our local government to adopt ordinances that protect water quality and enhance the quality of life in our community.
- Pick up and throw away pet waste in the trash. Animal and human waste contain bacteria and pathogens that make water dangerous for swimming.
- Refrain from pouring oil or chemicals onto the ground.
- Keep boats clean and avoid dripping fuel.
- Minimize fertilizers and pesticides in your yard. Nutrients in runoff contribute to algal blooms. See our Fertilization Guide for more tips.
- Consider replacing your lawn with deep-rooted plants that can hold soils in place.
Effectively managing a watershed requires cooperation, understanding and persistence, but the rewards of clean water are worth the hard work! Impervious surfaces might not seem like a big deal, but they have a huge impact on the health of our lakes and rivers. By understanding how they affect water quality and taking steps to reduce their negative effects, we can help ensure that these precious natural resources remain clean and safe for generations to come.
Thank you for doing your part to keep Lake Leelanau beautiful and healthy.