Geneva Lake Data

During August 2001, the Geneva Lake Environmental Agency conducted an aquatic plant survey to assess the condition of the submerged aquatic plant community. This plant survey was conducted as a part of the Geneva Lake Aquatic Plant Management Plan that the Agency is preparing as a part of the larger overall Geneva Lake Management Plan.

Some preliminary findings of the plant survey were interesting. Twenty-seven transects were used with each transect divided into five depth classes and a random depth within each class sampled. Twenty-three species representing 11 genera were identified. Two new species were found in this survey. Perhaps the most interesting finding of the survey was the significant increase in the aquatic plant called widgeon grass or nut grass, Ruppia currhhosa. This is a long stringy type plant with leaves that look very similar to its stem. Cut parts of this plant have been found floating in large mats in the middle of the lake and washed up on the shores.

It was by far the most abundant plant encountered in this survey. Although it was identified as being in the lake during the last aquatic plant survey in 1994, it was not found at the present densities.

Watch the Agency's web page for a more complete discussion on the aquatic plant survey and aquatic plant management plan. A complete report and a less technical summary are available at the Agency's office.

Another product of the aquatic plant survey was the preparation of an aquatic plant management plan (see map of recommended management below). In general the lake was divided into three separate aquatic plant management areas. The “No Restriction Zone” where it is recommended that there be no restriction on the aquatic plant management strategies if they are compatible with State requirements. The “Native Zone” are areas that have a diverse and healthy plant community and thus no management is needed or recommended unless conditions change. The “Watch Zone” is the largest area in size and includes areas were the plant community may need some minor management but for the most part is relatively stable. An overlay “Riparian Zone” can be located in any one of the other three zones but is restricted to only a 30 ft. wide strip running perpendicular to the shore and extends out into deeper water. This zone is to allow for riparian management of aquatic plants in their swim, mooring or pier areas.

Yellow colored results indicate an individual exceedence of the advisory criteria of 235 colonies per 100 ml of sample. Red colored results indicate an individual exceedence of the closing criteria of 1000 colonies per 100 ml of sample. An orange color of the geomean results indicate an exceedence of the criteria for the geomean of not less than 5 samples collected in 30 day should not exceed 126 colonies per 100 ml.

Every attempt will be made to keep this site updated and posted with the most recent data when received from the State Lab of Hygiene.