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Lake Riley

At 297 acres and average depth of 23 ft, 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 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.

Lake RIley - 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

Riley Lake 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

Size 297 acres
Volume 6,230 acre-ft
Average depth 23 ft
Max depth 49 ft
Watershed size 1,776 acres
Land draining directly into 818 acres
MPCA lake classification Deep
Impairment listing Mercury & Nutrients
Trophic status Eutrophic
Common fish Bluegill, Northern Pike, Yellow Perch, Yellow Bullhead
Invasive species Curlyleaf Pondweed, Eurasion Watermilfoil, Common Carp, Zebra Mussels

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