GENEVA LAKE DATA
Hydrography and Morphometry of Geneva Lake
SIZE
Hydrography and Morphometry of Geneva Lake
SIZE
Area of Lake 5,425 acres
Area of watershed 12,806 acres
Lake Volume 299,182 acre ft.(1)
Residence Time (2) 13.9 years
Acres of watershed per acre of Lake .3:1
(1) If the volume of water in the lake was spread out at a depth of only one foot the size of the lake would be 299,182 acres.
(2) The "residence time" is estimated as the time required for the full volume of the lake to be replaced once by the inflowing surface and ground waters associated with periods of normal precipitation.
Length of Lake . 7.6 miles
Length of Shoreline 20.2 miles
Maximum Width of Lake .2.1 miles
Minimum Width of Lake ..0.5 miles
Percent of Lake less than 10 ft 11
Percent of Lake 10 to 70 ft ..45
Percent of Lake more than 70 ft ..44
Mean Depth . .57 ft.
Maximum Depth
..
144 ft.
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 has 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 .
2006 ZEBRA MUSSEL COUNTS AT FOUR LOCATION
ON GENEVA LAKE, WALWORTH COUNTY WISCONSIN
All data expressed in mussels per meter squared
date
Lake Geneva
Hillside Rd.
Fontana
Williams Bay
7/06
8/06
10/06
All samplers were cleaned after each count.
2007 ZEBRA MUSSEL COUNTS AT FOUR LOCATION
ON GENEVA LAKE, WALWORTH COUNTY WISCONSIN
All data expressed in mussels per meter squared
date
Lake Geneva
Hillside Rd.
Fontana
Williams Bay
7/07
8/07
10/07
All substraits cleaned after counting.
* = Sampler found laying on bottom of lake.
** = Sampler missing.
2008 E-COLI COUNTS AT THE MUNICIPAL BEACHES, GENEVA LAKE
WI
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.
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.
TEMPERATURE AND DISSOLVED OXYGEN PROFILES
Conditions at time of sampling:
August 18,2008, 1025 CDT,Clear, W wind, 1 ft waves.
secchi 4.0 meter (9.2 ft.)
Provisional data subject to revision.
Lakes in temperate regions of the world follow a seasonal cycle: winter ice cover and inverse stratification where the warmest water is near the bottom and the coolest is at the top, a period after the ice melts called spring turnover when the lake is mixing from top to bottom, summer stratification when the lake establishes a warm top layer and a cold deep layer, and fall turnover when the lake mixes and is uniform from top to bottom.
The August 18,2008 temperature and dissolve oxygen showe the establishment of a strong summer stratification. Water temperature at the surface was recorded as 24.4C (75.9F). By definition a true thermocline exists between 10 meters (33.3ft) and 15.0 meters (49.5 ft) where temperature drops from 22.99 (73.2F) to 11.9 C (54.7.) Temperature slowly decreases with depth to the bottom where the water temperature is 6.4 c. (43.5 F)
The dissolved oxygen levels are a bit unusual for Geneva Lake summer stratification. Good oxygen levels, 8.6 mg/L, occur in the top 9 meters (29.7 ft) with a sudden drop at 10 meters (33.3 ft) to 4.8 mg/L. This sudden drop is due in part to the accumulation of organic material and detritus raining down from above. As this material accumulates there is an increase in biological activity causing decomposition and respiration to use the oxygen present with little if any oxygen being replenished. The accumulation of material at this depth is due to buoyancy changes associated with water density and the cooler water.
Interestingly, the deep waters (14m - 34m) shows a significant increase in oxygen levels. At 26 meters (85.8 ft.), oxygen levels are only 1.3 mg/L lower than surface oxygen levels.
Fish experience higher levels of stress when dissolved oxygen levels drops below 5 mg/L. Most fish species can not survive where dissolved oxygen is less than 2 mg/L. AS of the August 2008 sampling, oxygen levels dropped to 5 mg/L at 36 meters (118.8 ft), and less than 2 mg/L only on the bottom.
As summer progresses, the strong summer stratification will prevent the lower deeper waters from mixing. Dissolved oxygen will continue to drop in the deeper waters below the thermocline. Fortunatly the unusal summer of 2008 may result in a very small portion of the lower deep water running out of oxygen.
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.
TEMPERATURE AND DISSOLVED OXYGEN PROFILES
Conditions at time of sampling:
August 18,2008, 1025 CDT,Clear, W wind, 1 ft waves.
secchi 4.0 meter (9.2 ft.)
Provisional data subject to revision.
Lakes in temperate regions of the world follow a seasonal cycle: winter ice cover and inverse stratification where the warmest water is near the bottom and the coolest is at the top, a period after the ice melts called spring turnover when the lake is mixing from top to bottom, summer stratification when the lake establishes a warm top layer and a cold deep layer, and fall turnover when the lake mixes and is uniform from top to bottom.
The August 18,2008 temperature and dissolve oxygen showe the establishment of a strong summer stratification. Water temperature at the surface was recorded as 24.4C (75.9F). By definition a true thermocline exists between 10 meters (33.3ft) and 15.0 meters (49.5 ft) where temperature drops from 22.99 (73.2F) to 11.9 C (54.7.) Temperature slowly decreases with depth to the bottom where the water temperature is 6.4 c. (43.5 F)
The dissolved oxygen levels are a bit unusual for Geneva Lake summer stratification. Good oxygen levels, 8.6 mg/L, occur in the top 9 meters (29.7 ft) with a sudden drop at 10 meters (33.3 ft) to 4.8 mg/L. This sudden drop is due in part to the accumulation of organic material and detritus raining down from above. As this material accumulates there is an increase in biological activity causing decomposition and respiration to use the oxygen present with little if any oxygen being replenished. The accumulation of material at this depth is due to buoyancy changes associated with water density and the cooler water.
Interestingly, the deep waters (14m - 34m) shows a significant increase in oxygen levels. At 26 meters (85.8 ft.), oxygen levels are only 1.3 mg/L lower than surface oxygen levels.
Fish experience higher levels of stress when dissolved oxygen levels drops below 5 mg/L. Most fish species can not survive where dissolved oxygen is less than 2 mg/L. AS of the August 2008 sampling, oxygen levels dropped to 5 mg/L at 36 meters (118.8 ft), and less than 2 mg/L only on the bottom.
As summer progresses, the strong summer stratification will prevent the lower deeper waters from mixing. Dissolved oxygen will continue to drop in the deeper waters below the thermocline. Fortunatly the unusal summer of 2008 may result in a very small portion of the lower deep water running out of oxygen.