TMDL -Aquatic plants Volney

 

Section 1.0 Background Information

1.1 Site Description

Lake Volney, located in Le Sueur County Minnesota is a small lake at only 277 acres; however, Lake Volney has a maximum depth of 65 feet and a mean depth of 22.7 feet making it one of the deepest lakes in southern Minnesota. Lake Volney is situated in a watershed that is comprised of moderate to steeply sloping hills that have been cleared primarily for agricultural purposes. The total acreage within the Lake Volney watershed is 2,017 acres; most of the watershed is dominated by agricultural land use. The watershed to lake ratio for Lake Volney is 7:1 (Table 1.1 A.). The stratification of this lake is highly beneficial to the water quality of this basin because a large percentage of the phosphorus load is retained within the hypolimnion (bottom layer of lake during stratification) during a majority of the open water season. The combination of a small watershed-to lake ratio and the thermal stratification of Lake Volney give this waterbody a better than average chance for restoration.

Fifty-four percent of Lake Volney has a depth greater than 15 feet; therefore, approximately 46% of the surface area is within the littoral zone (less than 15 feet deep) that is capable of supporting plant growth. Although curly-leaf pondweed (CLP) has been found in Lake Volney, the growth of this species has not become problematic. Moderately dense stands of CLP were found in a small percentage of the lake in 2009. The sediment within Lake Volney has been found to be non-conducive to supporting extremely dense stands of CLP (Pers. Comm. Steve McComas of Blue Water Science, 2008). The overall macrophyte community found in Lake Volney is extremely limited, with a total of three species found during the point intercept surveys conducted in 2009. The absence of macrophytes within Lake Volney may partially explain the high frequency by which algae blooms occur. The ample supply of nutrients in coordination with an absence of shading from macrophytes allows for algae to grow relatively uninhibited.

The lack of emergent, submergent, and floating leaf vegetation on Lake Volney may limit the potential for this system to support game species such as northern pike, largemouth bass, and bluegill. Overall, a majority of the shoreline on Lake Volney has been developed; a portion of the eastern shoreline contains some natural vegetation. The restoration of natural shoreline vegetation and the enhancement of the existing submergent macrophyte community would likely be beneficial to the fishery and water quality in general.

1.9 B. Plant Survey and Analysis:

Staff from the Water Resource Center in coordination with the Minnesota Pollution Control Agency used a point-intercept sampling technique to provide a representative survey of the aquatic plant community on Lake Volney. Lake Volney was sampled twice in 2009; the first survey was completed on May 12th, when CLP is typically most abundant. The second survey was completed on August 11thwhen native species are typically most abundant. Overall, the aquatic plant community of Lake Volney is extremely limited. The deep morphometry and composition of sediment found in Lake Volney prohibits extensive macrophyte growth. Results 25

from both aquatic plant