By Madeline Seveland, Carver County Water Management
Did you know there is more than one type of lake? Lakes are categorized in many ways. Most often it is by the amount of algae and aquatic plants they have, but also by their size or hydrology (the area they drain), plant or animal communities, or the way humans use them (water supply, recreation, navigation, etc.). One type of lake common to Minnesota but often not in the headlines or listed as a destination is a shallow lake.
A shallow lake is on average less than 15 feet deep, although it may have a deep spot. The shallow depth allows sunlight to reach the bottom and as a result aquatic plants can thrive over most of the lake bed. Shallow lakes while often overlooked have a lot to offer, including wildlife, water quality and recreation opportunities. Shallow lake characteristics and benefits:
• Abundant sunlight and higher nutrient levels help support aquatic plant growth
• Denser shoreline vegetation holds sediment in place
• Aquatic plants use the nutrients, nitrogen and phosphorus, which otherwise would be in the water and cause algae blooms
• Lessen flooding damage by storing water and slowly releasing it throughout the year
• Diverse aquatic and shoreline plants create a spectacular display throughout warmer months
• Teeming with life of all sorts: plankton, water bugs, fish, turtles, waterfowl and other animals, providing vital habitat for the fish and waterfowl sought after by anglers and hunters
Unfortunately, many of our shallow lakes are underappreciated and polluted with turbid (muddy) water and algae blooms. Stormwater runoff from the surrounding area carries excess nutrients (phosphorus and nitrogen) to these lakes. This coupled with aggressive removal of aquatic plants results in green water thick with unappetizing algae, both aesthetically and odor. Shallow lakes with clear water and few aquatic plants are very rare and do not occur in urban areas.
Invasive species like Zebra Mussels, Eurasian Water Milfoil, Curly Leaf Pondweed, Rusty Crayfish, and Common Carp are examples of threats to shallow lakes. Bottom feeding carp can increase the nutrient problem by stirring nutrients back up into the water, while milfoil and pondweed can choke the lake and compete with native plants. Zebra mussels bring a whole bunch of problems including health hazards, declining fish habitat, and ruined boat motors.
There is much citizens can do to protect shallow (or any) lakes.
• Reduce runoff from your lawn with rain barrels or raingardens
• Always inspect boats, jet skis, docks and other water toys for invasive species when entering and leaving the water
• Don’t mow down to your shoreline but instead plant a buffer of native plants along the shore
• Keep a healthy aquatic plant population in the lake.
By better understanding shallow lakes, we can appreciate them for the great resources they are. If you’d like to learn more about shallow lakes, the Carver County Water Management is helping host “The Benefits of Being Shallow: A Shallow Lakes Forum” on Saturday April 12 from 8 a.m. to 11:30 a.m. Attendees will learn about shallow lake ecology, how lakes are managed by agencies, lake associations, and how to enhance and protect shallow lakes. Learn more and register at www.minnehahacreek.org/shallow-lakes.