Executive Summary         Rainbow Lake 2012          Adirondack Watershed Institute

The Adirondack Watershed Institute (AWI) sampled Rainbow Lake, Clear Pond and Lake Kushaqua once per month during June, July, and August 2012, near the deepest portion of each lake. AWI performed additional monitoring at several other locations each month in order to test for water quality degradation resulting from shoreline areas that contained a concentration of camps.

The color levels were elevated in all three lakes and color levels in Rainbow Lake and Clear Pond were the highest we have seen over all the years of this study.  These values were higher than past years due to the dry conditions and the concentrating of the water coming out of the surrounding swamps, bogs and wetlands. 

There has been no apparent significant change in the pH and alkalinity of Rainbow Lake, Clear Pond, and Lake Kushaqua over the period of record.  PH and alkalinity levels were typical during 2012 following the record breaking precipitation totals for the 2011 season.  These values are higher than those that are typical for Adirondack lakes and indicate that the lakes are moderately well-buffered (protected) against acidification.

Rainbow Lake, Clear Pond and Lake Kushaqua exhibited some loss of oxygen within their hypolimnia by the first time they were tested on June 27, 2012.  This is typical of Rainbow Lake and Clear Pond and has happened every year that we have studied these two lakes.  This shows that both lakes are not suitable for a natural reproducing cold water fishery.  Dissolved oxygen concentrations in the cold waters of the hypolimnion of Lake Kushaqua were low during July and August.  Theses dissolved oxygen values for Lake Kushaqua would cause stress to cold water fish but they would be adequate to support warm water fish.   

We now have a good historical record of dissolved oxygen profiles for Rainbow Lake dating back to 1954.  The historical dissolved oxygen data does show that the oxygen deficit in Rainbow Lake began to show itself in July by 1984.  This deficit had intensified during the 1990’s and had become worse every year until 2009.   During 2010, this oxygen deficit was slightly less and the 2011 and 2012 oxygen deficits were similar and less than the deficit for 2010.  The data does suggest that human impacts have definitely impacted Rainbow Lake in the past and may still be impacting the lake today. 

In all three lakes, it appears that there has been little change in trophic status since the mid – 1980’s.  The trophic indicators of chlorophyll a and Secchi transparency for Rainbow Lake, Clear Pond and Lake Kushaqua were within the mesotrophic range during 2012.   The final trophic indicator, total phosphorous, was actually in the oligotrophic range during 2012.  All three lake’s water quality for 2012, showed total phosphorous levels were the lowest we have seen when compared over the course of this study.  All three lakes had better than average chlorophyll-a levels that led to better than average Secchi disk transparencies for 2012.  Since total phosphorous concentrations were significantly lower than most years of this study, this is most likely due to the very dry conditions during the winter, spring and early summer for 2012.   

The Rainbow Lake Association should continue the present water quality monitoring program at least at the level sampled in 2012.  This past year was not a typical year due to the dry winter, spring and early summer.  It seems that lately no year is a typical year weather wise and that weather also has a large effect on Adirondack Lake’s water chemistry and trophic status.  Dissolved oxygen continues to be an issue in these lakes. The only way to tell if there is improvement or a continued decline in Rainbow Lake, Clear Pond or Lake Kushaqua’s water quality and a continued drop in dissolved oxygen is to continue to monitor next year and in the years to come to see if the trends reverse themselves under different weather conditions. 

In addition, monitoring provides an opportunity to select and assess the effectiveness of any management activities that may be implemented.  The Rainbow Lakes, like most Adirondack Lakes, have extremely limited water quality data sets, but by monitoring these lakes over the last fifteen years we now have one of the better long term lake data sets in the Adirondack Park.   Finally, by adding Lake Kushaqua, we have begun to build on the very limited data set that presently exists for that lake as well.