Gleason Lake is the primary receiving water within the subwatershed, and is classified by the DNR for shoreland management purposes as a Recreational Development Lake. Tables 4 and 5 below detail the physical and water quality characteristics of Gleason Lake and other lakes within the subwatershed. Since 2000 Gleason Lake has consistently been scored in the C-D grade range on the District’s annual lake report cards. The mean summer 2004 total phosphorus concentration was 104 μg/L, well in excess of the District’s 80 μg/L interim goal and the highest average concentration since 1997. It also exceeds the shallow lake standards being developed by the State of Minnesota and is in an impaired use condition, although it has not been formally designated an Impaired Water. Other large water resources in the subwatershed are Hadley, Kreatz and Snyder Lakes. Little or no water quality data is available for those lakes.
Table 4. Physical characteristics of lakes in the Gleason Lake subwatershed.
|Lake||Surface Area||Maximum Depth||Watershed to Lake Area Ratio||DNR Classification|
Source: Minnesota DNR
Table 5. Selected water quality goals and current conditions of lakes in the Gleason Lake subwatershed.
|Lake||1997 TP Goal||HHPLS TP Goal||1997-2004 Average TP||2004|
|TP (μg/L)||Chl-a (μg/L)||Secchi (m)||TSI|
*10% reduction from existing, provided it is greater than 25 μg/L ** Clarity as estimated by the University of Minnesota using satellite imagery.
Source: MCWD and Minnesota DNR/University of Minnesota
According to standards established by the MPCA, water quality in Gleason Lake is not supportive of swimming. Modeling performed for the HHPLS and for preparation of this plan indicates that phosphorus loading from runoff in the watershed cannot explain the total phosphorus concentrations in the lake. Internal loading from lake sediments is likely a root cause of the higher than expected in-lake TP concentrations and excessive algal blooms.
No water quality modeling was performed for Hadley, Kreatz, and Snyder Lakes as part of the HHPLS. The Regional Team recommended to the Board that baseline data be obtained, and that an appropriate goal would be a ten percent reduction in the in-lake total phosphorus concentration, provided that the existing level was greater than 25 μg/L. Given the water clarity as estimated by satellite imagery, it is likely the concentration is well in excess of 25 μg/L.