Water Quality Management
Overview
Managing Water Quality
Our lake water quality monitoring program gathers samples on District lakes throughout the early spring, summer, and fall. This is considered the growing season when the lake is the most productive.
We measure and monitor lake water clarity, conductivity, pH, temperature, and dissolved oxygen. We monitor aquatic invasive species (AIS), like Eurasian watermilfoil and zebra mussels.
In addition, we collect water samples that are analyzed for chloride, phosphorus and chlorophyll-a. The District has established goals for annual average Secchi reading, chlorophyll-a and phosphorus in our managed lakes.
Monitoring
Managed lakes are monitored twice a year, once in the spring and once in the fall. Lakes are monitored for known and unknown AIS, water clarity, conductivity, pH, temperature, and dissolved oxygen.
Chlorophyll-a
Chlorophyll-a measures the amount of algae and cyanobacteria in a waterbody. Algae and cyanobacteria are natural parts of a freshwater ecosystem. However, too much can create bad odors, aesthetic issues, and decreased levels of dissolved oxygen. Some cyanobacteria can produce toxins which are harmful to people and animals. Nutrients from fertilizers, septic systems, and stormwater runoff contribute to high chlorophyll-a levels.
Phosphorus
Phosphorus is a chemical element that is essential for living cells. When phosphorus is excessive, it can cause eutrophication and harmful algal growth. Excess phosphorus typically comes from things like:
- Lawn fertilizers
- Agricultural fertilizers
- Animal by-products like manure
- Wastewater treatment facilities
What is eutrophication?
When water becomes overloaded with nutrients, it can become eutrophic or experience eutrophication. There is an unnatural imbalance of nutrients in the water, such as nitrogen and phosphorus. This results in excessive algae growth, and the beginning of a chain reaction in the ecosystem. The excess algae blocks out sunlight to underwater plants. This reduces aquatic habitat, and lowers oxygen levels. When the algae eventually dies off and decompose, they consume even more oxygen in the water. This compounding effect creates an environment with oxygen levels too low to support most aquatic life. Eventually, the waterbody can become anoxic, and the dissolved oxygen in the water is 0. When a lake becomes anoxic, it is considered dead and uninhabitable.
Chloride
Chloride is a chemical commonly used to melt ice during the winter. It makes its way into the water through stormwater runoff. Chloride is toxic to fish, aquatic insects, and amphibians. It also harms plants, soil, pets, infrastructure, and can contaminate drinking water.
Water Clarity
Water clarity is an indicator of water quality. It is a misconception that all lakes and streams should be completely crystal clear. In fact, a healthy lake will often have some level of sedimentation and many aquatic plants present.
Management
When a invasive species is detected, the District takes action to manage the population. It is impossible to know when exactly a aquatic invasive species enters a lake. It is common for invasive species to be introduced through recreational use of a lake. That is why it is important to always remember to Clean, Drain, Dry before enter and exiting any body of water. Shallow and productive lakes like those in the watershed are ideal habitats for aquatic invasive species to thrive and outcompete native species.
Read the SWWD Lake Management Plan
AIS in the watershed
Eurasian watermilfoil (Myriophyllum spicatum) and Curly-leaf pondweed (Potamogeton crispus) and both found in the watershed. While these species are both found throughout the twin cities metro, it is still important to manage their populations. Managed waterbodies are assessed for treatment during twice annual monitoring events and prescribed treatments if necessary.
Why are some lakes treated?
Invasive species like Eurasian watermilfoil (EWM) and Curly-leaf pondweed (CLP) are a nuisance. They make recreation like fishing, canoeing, or kayaking quite difficult. Additionally, CLP grows in the winter and spring before other native species. After CLP dies, it releases nutrients into the water that drive ongoing algae blooms.
How are lakes treated?
When a herbicide treatment is deemed necessary, a permit is obtained from the MNDNR. In-lake herbicide treatments have been around for a long time and studied extensively. Research shows that they do not harm fish, mammals, or aquatic insects, and are safe for humans and pets. When a treatment occurs, signage is clearly posted to notify lake users of ongoing treatments and recommended uses.
Check out this video on in-lake treatments on Colby Lake to learn more about how SWWD manages aquatic invasive species
Abby Tekiela
Staff Contact
Questions? Reach out to Abby Tekiela, Water Resources Program Manager, at Abby.Tekiela@swwdmn.gov or call 651.728.6827.