Lake Minnetonka water quality is monitored by the Minnehaha Creek Watershed District.  The MCWD has ten years of history on the water quality of Lake Minnetonka  as seen below for 20+ bays and lakes within the lake.

The Minnehaha Creek Watershed District Grades consider what is average or normal for lakes in a given area. What is a “C” in one part of the country might not be a “C” elsewhere. However, within the seven-county metro area, grades can be compared.

Lake Minnetonka water quality is as follows:
Grade A: Crystal clear, beautiful. These lakes are exceptional and can be enjoyed by recreation users without question or hesitation.
Grade B: Generally good water quality but algae may limit swimming, particularly toward the end of the summer.
Grade C: Average quality. Swimming, boating, and fishing may be undesirable relatively early in the season. Algae blooms occasionally.
Grade D: Severe algae problems. People are generally not interested in recreation on these lakes.
Grade F:  Not enjoyable. The lake would have severe limitations to recreational use.

Lake Minnetonka Subwatershed

* Bays not monitored due to water quality similar to adjacent bay
– Water body not monitored in 2017
n/a insufficient data