2.5.1 Lakes

Long 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 5 and 6 below detail the physical and water quality characteristics of Long Lake and other major lakes within the subwatershed.    Long Lake is 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 76 μg/L, well in excess of the District’s 40-50 μg/L goal and the highest average concentration since 1997.  It also exceeds the 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 major lakes in the subwatershed are Mooney Lake, Holy Name Lake, Wolsfeld Lake, and Tanager Lake.  Tanager Lake is monitored as part of the District’s monitoring program, but the other lakes are not and little or no water quality data is available for them.

Table 5.  Physical characteristics of lakes in the Long Lake subwatershed.

Lake

Surface Area (acres)

Maximum Depth (ft)

Watershed to Lake Area Ratio

DNR Classification

Long

144

38

21:1

Recreational Development

Mooney

60

10

7:1

Recreational Development

Holy Name

65

7

6:1

Recreational Development

Wolsfeld

33

26

46:1

Natural Environment

Tanager

74

23

140:1

Recreational Development

Source: Minnesota DNR.

Table 6.  Selected water quality goals and current conditions of lakes in the Long Lake subwatershed.

Lake 

1997 TP Goal (μg/L)

HHPLS TP Goal (μg/L)

1997-2004 Average TP (μg/L)

2004

TP (μg/L)

Chl-a (μg/L)

Secchi (m)

TSI

Long

50

40-50

59

76

40

1.2

64

Mooney

N/A

N/A

143*

N/A

N/A

<0.5**

N/A

Holy Name

N/A

N/A

N/A

N/A

N/A

<0.5**

N/A

Wolsfeld

50

N/A

N/A

N/A

N/A

0.5-1.0**

N/A

Tanager

90

70

95

118

80

1.1

68

TP = Total phosphorus concentration

*Average based on pre-1996 data  ** 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 Long Lake is partially supportive of swimming.  An alum treatment applied in 1996 briefly provided some improvement in clarity; however, clarity and water quality in general has been slowly returning to pre-treatment levels. 

Tanager Lake has scored in the C-D grade range on the District’s annual lake report cards.  The mean summer 2004 total phosphorus concentration was 118 μg/L, well in excess of the District’s 70 μg/L interim goal.   It is likely that phosphorus from Long Lake Creek is contributing to the higher than expected in-lake concentration in Tanager.  No water quality modeling was performed for Mooney, Holy Name, and Wolsfeld Lakes as part of the HHPLS, and no water quality goals were established.