IMPAIRED Waters: Delisting decisions
Section 303(d) of the Clean Water Act requires US states to assess their waterways every two years and publish a list of “impaired” waters. When agencies like Minnesota’s Pollution Control Agency determine a waterway is “impaired,” they must develop plans to implement restoration activities.
An eight inch in diameter black and white disk used to check for clarity of water. (In Minnesota they use a white disk)
TO USE: Lower disk into the water until you can’t see it anymore, then count marks placed at every six inches on the rope to see how far down it goes.
The further down you are able to read the disk, the higher the clarity of the water.
TAKING A READING: a low clarity reading reflects excess sediment and algae in the water. When sunlight penetration is reduced, it can be harmful to plants, insects, and fish communities.
HOWARD LAKE SI AMONG THE 40 PERCENT OF MINNESOTA’S RIVERS AND LAKES THAT HAVE BEEN FOUND TO BE “IMPAIRED” BY FARM RUNOFF, BACTERIA, MERCURY OR OTHER POLLUTANTS. CURT FORST THINKS IT CAN BE SAVED. As a volunteer water monitor, Curt takes samples on Howard Lake each month between May and September. He measures of the clarity of the water using a secchi disk, takes water samples for phosphorus and Chlorophyll a, and observes a range of activities taking place on the lake: recreation, weather, temperature, and wave action. Curt thinks the excess nutrients in this lake come from fertilizer runoff from nearby farms, lawns at homes along the lake, and from nearby towns.