2.5.4 Wetlands

Approximately 34 percent of the land area within the Lake Virginia subwatershed is shown on the National Wetland Inventory as wetland (see Table 7). 

Table 7.  National Wetlands Inventory wetlands in the Lake Virginia subwatershed.

Circular 39 Type

Area (acres)

Cowardin Class

Area (acres)

Seasonal

35.1

Emergent

421.3

Shallow Marsh

386.2

Forested

45.2

Deep Marsh

3.9

Scrub-Shrub

36.4

Open Water

843.5

Unconsolidated Bottom

847.4

Scrub-Shrub

36.4

 

 

Forested

45.2

 

 

Total

1,350.3

 

1,350.3

Source: Minnesota DNR.

In 2001-2003 the District undertook a Functional Assessment of Wetlands (FAW) on all wetlands greater than one-quarter acre in size.  This assessment used a variant of the Minnesota Routine Assessment Method.  In contrast to Table 7 above, which shows wetland acreage and type from the National Wetlands Inventory completed in the 1980s, Table 8 below shows the acreage and type as assessed in the field.   Using the results of that analysis, individual wetlands were assigned to one of four categories – Preserve, and Manage 1, 2, or 3 (see Table 9 and Figure 12).   Wetlands that were evaluated as Exceptional or High on certain ecological or hydrologic values were assigned to the Preserve category.  The balance of evaluated wetlands were assigned to a category based on this assessment of current functions and values, with Manage 1 wetlands exhibiting higher values and Manage 2 and 3 moderate or lower values.   Refer to the Functional Assessment of Wetlands (2003) for details of methodology, classification, and management recommendations.

Table 8.  Dominant wetland type in the Lake Virginia subwatershed as assessed in the Functional Assessment of Wetlands.

Circular 39 Type

Area (acres)

Seasonal

20.6

Wet Meadow

145.8

Shallow Marsh

192.5

Deep Marsh

55.9

Open Water

112.2

Scrub Shrub

84.0

Forested

56.8

Lake

781.2

Not typed

6.2

TOTAL

1,455.2

Note: Based on field assessment.  Excludes those areas determined in the field not to be wetlands, and stormwater ponds clearly excavated out of upland.   Includes some small areas that were not field assessed.

Source: MCWD 2003 Functional Assessment of Wetlands.  See Figure 11. 

Table 9.  Wetland management classifications of wetlands in the Lake Virginia subwatershed as determined in the Functional Assessment of Wetlands.

Classification

Number

Area (acres)

% of total

Preserve

47

296.2

39.3

Manage 1

33

213.0

28.3

Manage 2

60

75.5

10.0

Manage 3

65

168.4

22.4

TOTAL

 

753.1

 

Note:  The FAW excluded large lakes and wetlands less than ¼ acre in size; those areas are included in the NWI, so total will not match Tables 7 or 8.

Source:  MCWD 2003 Functional Assessment of Wetlands.  See Figure 12.

Many of the Preserve wetlands were classified as such because of their exceptional or high vegetative diversity, or fish or wildlife habitat value (see Figure 13).  Several are also positioned in the subwatershed to provide substantial downstream water quality and quantity benefits from stormwater storage and filtering. 

There are several wetlands in the subwatershed that the FAW identified as being of high or moderate restoration potential (see Figure 14), including a wetland through which Minnewashta Creek flows on its way to Lake Virginia.