Litchfield Park Lakes Water Quality Report Program Update: 2017
Adirondack Watershed Institute
Corey Laxson, Elizabeth Yerger, Hunter Favreau, & Daniel Kelting
The Adirondack Watershed Institute began monitoring the limnology and water quality of Lake Madeleine and Heavens Lake in 1994. The objectives of this work are to track acid and trophic characteristics of the lakes, and to provide recommendations for acid mitigation and lake management. The lakes have been treated with limestone sand at regular intervals since 1986; however, the lakes have not been limed in last four years. This provides us with an opportunity to examine how the chemistry of the lakes has responded to a reduction in lime application. Understanding the response to decreased management effort is important because amendments to the Clean Air Act in 1990 have resulted in a substantial decrease in acid deposition and recent research reveals that many acid impacted lakes are showing signs of natural recovery.
Lake Madeleine provides cold water and high concentration of dissolved oxygen throughout most of the field season. Dissolved oxygen is depleted to low concentrations in the bottom few meters of the deepest section and this pattern is common in the historical data.
Heavens Lake provides suitable thermal conditions for brook trout. During the summer months optimal conditions are restricted due to warm surface water and anoxic bottom waters.
The average secchi disk transparency of Lake Madeleine in 2017 was the lowest observed value in the historical data set. Overall, the transparency of the lake is exhibiting a significant downward trend. This pattern does not appear to be related to nutrients or algal productivity, as chlorophyll concentration has not exhibited any significant trend and phosphorus concentration has been decreasing over time. Analysis of 122 Adirondack lakes, as well as recent scientific publications, suggests the decreased transparency may be a regional response related to changes in climatic patterns and acid deposition recovery.
As expected, the reduction in the rate of lime application to Lake Madeleine has resulted in decreased ANC and calcium concentration. Despite these reductions, the pH of the lake has not been affected; it remains circumneutral with no significant change since liming stopped in 2013.
The pattern in Heavens Lake is similar, although Heavens’ pH tends to be lower than Lake Madeline’s. The higher elevation, low retention time, and shallower soils of Heavens watershed offer less natural buffering ability. We observed a significant reduction in ANC and calcium since the period of biennial lime application. Despite the reductions in buffering, the pH of the lake has actually exhibited a slight, yet significant increase.
The lakes provide a suitable chemical environment for the primary species of interest. Brook and lake trout are more acid tolerant than other freshwater fish species. Although the optimal pH range for survival and reproduction appears to be between 6.5 and 8.0, the tolerance range is much wider and likely between 4.0 and 9.0 pH units. The Litchfield park lakes are mildly acidic to circumneutral, suggesting the acidity is not an issue of concern at this time.
The Ca:H ratios of both Madeleine and Heavens Lakes rarely fall below the threshold level of 10, in fact during the vast majority of observations they are near the optimal value of 100, suggesting that the chemistry of these lakes is favorable to native trout species.
We recommend that the acid mitigation strategy employed at Litchfield Park be changed from biennial application to only when necessary. The liming option should be discussed when the pH of either of the water bodies falls below 6.0 pH units.