The Minnehaha Creek Watershed District s lake grading method was developed in 1989. The grade shows how your lake measures up compared to other area lakes. Grades are an indicator of the perceived condition of the open water. Three water quality parameters are combined to calculate each lake grade (see below). There are, of course, other factors that contribute to lake condition for example, aquatic plants, fisheries, harmful chemicals, over use, etc. Understanding Your Lake Grade The 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. But, within the seven county metro area, grades can be compared. Grade Relative Ranking Description A 90% and up Crystal clear, beautiful. These lakes are exceptional and are enjoyed recreationally without question or hesitation. B 70 90% These lakes generally have good water quality but algae may limit swimming, particularly toward the end of summer. C 30 70% Average quality. Swimming, boating and fishing may be undesirable relatively early in the season. Algae blooms occasionally. D 10 30% These lakes have severe algae problems. People are generally not interested in recreation on these lakes. F Lowest 10% Not enjoyable. Such a lake would have several limitations to recreational use.
Factors in Your Lake Grade TP is total phosphorus. Increased phosphorus relates closely to increased algae, frequency of algae blooms and the increased quantity of blue green algae. CHL A is chlorophyll a or the green pigment in plants. Chlorophyll a is essential to photosynthesis. A measure of its presence in water estimates algae abundance. SD is the Secchi disk depth (water transparency). The deeper the Secchi disk is visible in the lake, the clearer the water appears. Improving Low Lake Grades Getting a better lake grade takes extra work. It might mean changes in drainage patterns, filtration or detention of storm water. Not all lakes have the same potential (shallow lakes can only so much water transparency). It s up to everyone to help water quality live up to its potential. Monitoring The District s waters are monitored on a regular basis. Data is collected by the MCWD, Three Rivers Park District, the Minneapolis Park & Recreation Board and Metropolitan Council Environmental Services. Those data are used to note and correct problems wherever possible. Data are summarized and studies are conducted to identify potential improvements. More Information Your yard and home might be a bad influence on your neighborhood lake. Keep your grades up prevent wastes (i.e., pet waste, lawn clippings, fertilizer or other chemical waste) from entering the water through the street storm drains. Storm drains are a direct, untreated route to the nearest lake or stream.
Lake Water Quality Grades, 2003 2012 Lake Minnetonka Subwatershed Bay/Lake/Pond 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Black C+ C+ C+ B+ B- B B- C+ Carman B+ B+ B A- A A B+ A- Carsons A A- B+ B+ A A A A- A Cooks B B- B- B C+ B B B B- B- Crystal A- B+ B B- B- B+ B A B- A- Forest D C C- D D+ D+ D C C- C- French Lake Marsh N/A N/A Gideon A A- A Grays A A B+ B A B+ A- A A Halsted D+ C- C- D+ D D+ D D D D- Harrisons D+ C C- D D+ C- C- C D+ D+ Jennings D+ C- D D F D C- D D D- Lafayette B+ B+ B- A A A A- A Libbs B- B+ N/A N/A Lower Lake North B+ B+ B+ A A A A A Lower Lake South A A A- B+ B+ A A A A- A There was insufficient data to calculate a lake grade N/A A lake grade was not calculated because the Secchi disk was visible at the bottom of the lake and/or obstructed by vegetation during one or more monitoring events
Lake Water Quality Grades, 2003 2012 Lake Minnetonka Subwatershed (continued) Bay/Lake/Pond 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Marion A A A Maxwell C+ B C+ C+ C B C+ B- B- C+ North Arm B- B B- B- C+ B B- B- B- C+ Peavey C C C D C- C+ C C C C- Phelps B+ B A- A- A B+ B+ Priests C- B- C+ C+ C+ C+ C+ C C- Shaver N/A N/A Smithtown B+ A- B B A B+ A B+ B+ Spring Park A A- B+ B B A- A- A A- A- St. Albans A A A B+ B A A A A- A Stubbs C- C C- D+ C- C C C C D+ Wayzata A A A- B+ B A A A A A West Arm D+ C C D+ D D+ C- C C- D West Upper B+ B A- B B- B+ B+ A B B- William --- C+* N/A* N/A* There was insufficient data to calculate a lake grade N/A A lake grade was not calculated because the Secchi disk was visible at the bottom of the lake and/or obstructed by vegetation during one or more monitoring events
Minnehaha Creek Subwatershed Brownie C+ C+ C+ C- C- Calhoun A A A A A- A A A A A Cedar B+ A- B+ B- B+ B B+ B B+ B+ Cobblecrest** F F F F F F F D --- Diamond C- D F F F D- D+ D N/A N/A Grass F C+ C C D+ D- Harriet A A A B+ A- B+ A A A A- Hiawatha C+ C+ B- C+ D+ C D+ C+ B- C- Isles C- C B- C C C C+ C C+ C Mother N/A N/A Nokomis C+ D+ C+ C- C- C C- C C+ C- Pamela Pond N/A N/A Powderhorn --- D+ C C- C C- C+ C D+ D+ South Oak** D D+ F F --- --- C D Twin** D F D- D F D- F D- F D- Westling Pond N/A F Windsor F D There was insufficient data to calculate a lake grade N/A A lake grade was not calculated because the Secchi disk was visible at the bottom of the lake and/or obstructed by vegetation during one or more monitoring events The lake was monitored by Minneapolis Parks and Recreation Board ** The lake was monitored by Metropolitan Council Environmental Services Citizen Assisted Monitoring Program
Christmas Lake Subwatershed Christmas A A- A A A A A A A A Dutch Lake Subwatershed Dutch D D C C C C C C C C- Schutz Lake Subwatershed Schutz C+ C- C C+ C+ C B- C C C- Gleason Lake Subwatershed Gleason D C- C- D D+ D+ C- C C C+
Lake Virginia Subwatershed Minnewashta A B+ A- B B+ A- B+ B+ B+ B+ Minnewashta (South Bay)** B+ A B- Virginia C --- C+ C C C- C C C C- St. Joe** A- A B A A- B+ A- A- A- Tamarack C** C** C** C** B** B** B** A-* B* B+* ** The lake was monitored by Metropolitan Council Environmental Services Citizen Assisted Monitoring Program Langdon Lake Subwatershed Langdon F F D F D- F D+ C- D+ F Saunders B+ N/A* B-* B-* Painter Creek Subwatershed Academy Marsh N/A F Katrina Lake F D+ F D The lake was monitored by Three Rivers Park District
Long Lake Creek Subwatershed Dickey's B B* B* B* Long C- C- C C- C- C C- C C- D+ Lydiard A A-* B+* A-* Mooney B- D C N/A* ---* Tanager D D- D D- D D D+ D D- Six Mile Marsh Subwatershed Carl Krey B B+ A- B Church B C B- C East Auburn B- C C C* C Kelser's Pond C+ C* C+* C+ Lundsten N C C+ B- --- N/A N/A Lundsten S F Marsh N/A N/A N/A Mud F F F F Parley D --- D+ D- D- D+ C- D+ D D+ Piersons A- --- B- B B+ B+ B A- A- A- Steiger C B- C+ C+ B B B- Stone C C+ B+ A- A- Turbid C+ C C- --- C C- Wassermann C- D+ D D+ D C- C- D C- D West Auburn B- B- B- A- B B+ B B+ B- A- Zumbra B B B- B B B+ A- A- A- A- The lake was monitored by Three Rivers Park District