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Lake Ann

Located in Chanhassen, Lake Ann is at the headwaters of Riley Creek. Over the past 40 years, Lake Ann has consistently met clean water standards set by the Minnesota Pollution Control Agency (MPCA).

Lake Ann is classified as a “Deep Lake” by the MPCA. To be considered healthy, the lake must have very low average phosphorus and chlorophyll-a levels and an average water clarity of 1.4 meters (4.6 feet) or greater.

From June through September every year, District staff visit this and other lakes every two weeks to collect water samples and take readings.  Samples are sent to a laboratory to be tested for nutrients and other compounds. Staff also measure water clarity by lowering a Secchi disk into the water and measuring how deep it goes before it is no longer visible. The data indicates the lake’s health based on standards set by the MPCA.

Lake Ann - Water Quality Grade

Lake WQ Grade A.pngRPBCWD staff assigned this letter grade to the lake based upon how well it is meeting water quality goals. Learn more about lake water quality grades.

For more information about the water quality and grades for lakes monitored in the District, visit the lake factsheets page.

Lake Factsheet

Lake Ann Factsheet

Several water quality parameters are monitored for the lake including Total Phosphorus, Chlorophyll-a, and water clarity. The results are compared to standards set by the MPCA. The District also collects data about native aquatic plant populations and invasive species. Learn more in the lake factsheet.

Open Factsheet

Watershed Location

Lake and Watershed Characteristics

Lake size 119 acres
Volume 2,005 acre-ft
Average depth 16.8 ft
Maximum depth 40 ft
Watershed size 257 acres
Land draining directly into lake 105 acres
MPCA lake classification Deep lake (>15 feet deep)
Impairment listing* Mercury
Trophic status Mesotrophic
Common fish Bluegill, Northern PIke, Largemouth Bass, Yellow Perch, Pumkinseed Sunfish
Invasive species Curlyleaf Pondweed, Eurasian Watermilfoil, Common Carp, Brittle Naiad, Zebra Mussel

*For more information about waterbody impairments, visit the Minnesota's Impaired Waters List webpage managed by the Minnesota Pollution Control Agency.


DNR LakeFinder

Get information on water levels, fish stocking, and water clarity.


MPCA Surface Water Data

Find historical lake and stream water quality data.


Metropolitan Council

View and download information on lakes, rivers, streams, rain gauges