2023 Lake Health Report

Testing of Finger Lake was completed in 2022 as it has been over the past years, with four testing events occurring between ice out and September. Testing was completed by Bill Abba and Sue Sazama and all results were reported to the WDNR for assessment. Relatively minor changes in test results from the past few years were noted and will be detailed below. Overall, Finger Lake continues to be in very good condition with no significant warning signs apparent.

The most significant change was in water level. As has been the case the last two years, water levels on the lake were a bit lower than the very elevated levels of a few years ago. Reduced snow fall and rainfall are the likely reasons. The lake has a very small watershed so there is limited drainage into Finger Lake from the surrounding watershed area. Lake levels in Finger Lake are primarily impacted by snow and rain amounts during the year and the resulting impact on the local water table. Much of the water in Finger Lake is derived from the many springs in the lake pulling water in from the water table. Though a bit down from the past two years, the lake water level still remains at or slightly above the average for the lake.

The other somewhat minor change was the water color lightening up from the dark brown color seen since the extremely high water levels of a few years ago. This brown color is caused from the drainage of tannins into the lake from surrounding land areas. Tannins are a natural plant material released from decaying plants, particularly pine trees. The lower snow and rainfall of the past few years has washed less tannins into the lake so the intensity of the brown color has reduced. Tannins themselves cause little issue on the lake but the dark water color does reduce light penetration. Light penetration increased slightly adding about a foot to the average secchi disk reading. The primary impact of this increasing light penetration is encouraging plant growth, but the impact appears modest at this point.

The most significant positive impact of the reduced light penetration of the past years caused by the high tannin levels is that the Southern Naiad nuisance plant has been held at bay. We have not seen the massive growth of this plant since the water levels on the lake have been elevated. As the lake water level returns to historical levels, we can expect further clearing of the brown tannin color and increasing light penetration potentially resulting in more problematic growth of Southern Naiad. While there is limited information on what drives Southern Naiad growth in Finger Lake, the light penetration theory seems most plausible and is consistent with the WDNR assessment.

Dissolved oxygen levels on the lake were again impacted, also likely by the reduced light penetration and the lower resulting plant growth. As has been the case in recent years, there was no oxygen in water deeper that fifteen feet. Oxygen levels in the top fifteen feet were very good. The oxygen levels redistribute all the way to the bottom after fall turnover in September so for the fall, winter, and very early spring seasons, there is oxygen throughout the lake depths. This is a common situation in deep water lakes, like Finger Lake, found in northern Wisconsin.

Overall, a very good report on lake health.

Bill Abba