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Common Pond & Lake Concerns
The primary purpose of many ponds in Rosemount is to collect stormwater runoff (rain and snow melt) and reduce the risk of flooding. The City performs inspections of stormwater ponds on about a 5-year cycle to make sure that ponds function as designed.
What you see as weeds may be part of a normal pond environment. Native aquatic plants are essential to pond health. Plants provide food and shelter for wildlife such as birds and fish. Plants also absorb excess nutrients from the water and prevent shoreline erosion. Knowing what a healthy pond looks like can help adjust your expectations for your pond's appearance.
Sometimes, invasive plants may be a problem. If one plant seems to be taking over your pond, try to identify what it is. Check out the Minnesota Department of Natural Resources (DNR) guide to invasive aquatic plants.
Photo Credit: Minnesota Pollution Control Agency
If tiny green plants are floating on the water's surface, you probably have duckweed. These tiny, native aquatic plants provide food and shelter for wildlife. Green blobs or fuzzy strings? You may have filamentous algae. If the water itself is green, it's probably microscopic plankton algae. Some algae is normal, but too much algae reduces water clarity, which upsets plant growth and the natural food chain.
The best way to reduce algae is to reduce the amount of phosphorus and other nutrients entering your pond. For tips, scroll down to "Help Protect Water Quality" at the bottom of this page. Keep in mind that the MN DNR regulates the control of algae and aquatic plants such as duckweed in any waterbody designated a "Public Water."
Photo Credit: Minnesota Pollution Control Agency
In early spring, after ice-out, dead fish may be seen along the shoreline. Usually this is a common occurrence after a harsh winter when ice and snow limit the amount of sunlight reaching into the water. With little light, aquatic plants photosynthesize less, producing less oxygen. Low oxygen levels in the water cause some fish to suffocate. A similar situation can happen in summer after an algae bloom and subsequent die-off. Decomposition of the algae uses up oxygen, making less available for fish.
Photo Credit: Minnesota Pollution Control Agency
Smells from a pond are usually caused by plant decomposition and will subside over time. An algae bloom and subsequent die-off is often the culprit. The best way to prevent future smelly problems is to prevent algae blooms. This is best done by reducing the amount of phosphorus and other nutrients entering your pond.
For tips, scroll down to "Help Protect Water Quality" at the bottom of this page.
Photo Credit: Minnesota Pollution Control Agency
Help Protect Water Quality in Ponds & Lakes
Water quality is an important issue that impacts everyone, and we are all responsible for protecting our water resources. Here are some simple things that you can do to help.
- Reduce runoff: When rain and snowmelt run off your driveway, it washes pollution into storm drains, which lead straight to your neighborhood pond. Reduce runoff by directing your downspouts onto your yard, not your driveway. You can also install a rain barrel or build a rain garden to capture runoff.
- Learn about our Stormwater Rebate Program.
- Keep fertilizer on the lawn: It's illegal to leave fertilizer on hard surfaces such as driveways, sidewalks, and roads because the fertilizer can wash into storm drains. Also, fertilizer may not be used within 20 feet of the end of any wetland, pond, or lake.
- Rake leaves, grass clippings, branches and other yard waste OFF the street: Yard waste debris can be unsafe for traffic and may cause flooding by plugging up storm drains. Learn about composting and where to take yard waste.
- The Recycling Association of Minnesota (RAM) offers compost bins for sale. Most distribution dates occur in spring and early summer. The first several hundred Dakota County residents to order may be eligible for an additional discount offered by the County at checkout – use promo code ‘Dakota’ at checkout.
- Pick up pet waste and put it in the garbage: Rain and snowmelt runoff can wash pet waste into storm drains and ponds. As it decomposes, the waste releases bacteria (E. coli, salmonella), parasites (Giardia), and nutrients (such as phosphorus) into the water.
- Wash vehicles on the lawn, not on your driveway: The soapy water won't hurt your grass, but it it ends up in a storm drain it can harm your neighborhood pond.
- Reduce or eliminate winter salt use: Instead of salt, try using sand or non-clumping kitty litter for traction on ice. Shovel snow as soon as possible to keep your walkways clear and prevent ice-buildup so that you don't need salt. If you do use salt, read package instructions so that you don't over-apply. Keep in mind that, in general, you need less than 1 pound of salt per 250 square feet (roughly the size of two average parking spaces). This amount may be less than you think - a 12-ounce coffee mug holds about a pound of salt.
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