Lake Riley
At 297 acres and average depth of 23 feet, Lake Riley is the largest lake in the Watershed District. It is located on the boundary of Chanhassen and Eden Prairie and is a popular summer recreation spot.
Lake size: 297 acres
Watershed size: 1,776 acres
Average depth: 23 feet
Maximum depth: 49 feet
DNR - Lake Riley depth mapDNR Shoreland classification: Recreational Development
MPCA classification: Deep lake (average depth greater than 15 feet)
MPCA Impaired Waters status: Impaired for nutrients, Impaired for mercury in fish tissue, Impaired for fish bioassessments
Invasive species: Eurasian Watermilfoil, Curlyleaf Pondweed, Common Carp, Zebra Mussel, Purple Loosestrife
Water Quality
Lake Riley 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.
For water quality summaries for this and other lakes, visit the factsheets page.
Lake Grade
RPBCWD 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 waterbody impairments, visit the Minnesota's Impaired Waters List webpage managed by the Minnesota Pollution Control Agency.
