Executive Summary

Rainbow Lake 2011          Adirondack Watershed Institute

This report presents the findings of the 2011 monitoring program for Rainbow Lake, Clear Pond, and Lake Kushaqua. The report includes an executive summary, a description of the monitoring methodology, a summary of results for each water quality parameter, an analysis of water quality trends, conclusions and recommendations. A glossary of lake and watershed terms is presented in Appendix A. All water quality data are presented in Appendix B.

 

The Adirondack Watershed Institute (AWI) sampled Rainbow Lake, Clear Pond and Lake Kushaqua once per month during June, July, and August 2011, 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 in 2011 for Clear Pond were elevated but the color levels in Rainbow Lake and Lake Kushaqua were the highest we have seen over all the years of this study.  These values were higher than past years due to the record precipitation and water levels draining the surrounding swamps, bogs and wetlands.  The pH values were lower than the typical pH values we have seen over the course of the period of study for these water bodies due to the record breaking precipitation totals for the 2011 season and the high water levels.

 

Rainbow Lake and Clear Pond exhibited a high degree of oxygen depletion in the bottom waters.  We now have a good historical record of dissolve 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 1984.  This deficit had intensified during the 1990's and had become worse every year until 2003.  This deficit was slightly improved in 2010.  During 2010, this oxygen deficit was slightly less and the 2011 oxygen deficit was similar and a little less than the deficit for 2010.  This deficit could be caused by human impacts around Rainbow Lake from the 1960's, 1970's, 1980's or up to present day.  It is impossible, based on our data set, to say if this is a problem that was caused by humans in the 1960's and 1970's and is no longer occurring, or if this problem began in the 1960's and is still going on to this day.  The data does suggest that human impacts have definitely impacted Rainbow Lake in the past.

 

In all three lakes, it appears that there has been little change in trophic status since the mid-1980s.   Trophic indicators (total phosphorus, chlorophyll a and Secchi transparency) for Rainbow Lake, Clear Pond and Lake Kushaqua were within the mesotrophic range during 2011.  Rainbow Lake, Clear Pond and Lake Kushaqua’s water quality for 2011, showed total phosphorous levels were higher than in 2010 but about average when compared over the course of this study.  Rainbow Lake’s transparency for 2011 was one of the worst we have seen in more than twenty years and significantly worse than 2010.  Clear Pond’s transparency for 2011 tied with 2002 and 2009 for the worst transparency we have seen over the course of this study.  Lake Kushaqua‘s transparency was also one of the worst years we have seen and much lower than in 2010.  Since total phosphorous concentrations were not significantly different than most years of this study, the very low Secchi disk transparency readings for 2011 are most likely due to the record precipitation and runoff resulting in record color levels for the water that drains out of the swamps, bogs and wetlands into Rainbow Lake and Lake Kushaqua and to a lesser extent Clear Pond.

 

There is generally a positive relationship shown between chlorophyll a and total phosphorus concentrations, so that chlorophyll a concentrations usually increase with increased total phosphorus concentrations.  Rainbow Lake, Clear Pond and Lake Kushaqua had an average concentration of total phosphorus and a corresponding average concentration of chlorophyll a in 2011.  Since algae and chlorophyll a concentrations do not seem to be above average, Secchi disk transparency is significantly lower due to high color levels and not high algae levels.

The Rainbow Lake Association should continue the present water quality monitoring program at least at the level sampled in 2011.  This past year was not a typical year due to the record precipitation and water levels.  We now know that high water levels cause a decline in all three lakes clarity, especially Rainbow Lake and Lake Kushaqua, but this is not due to phosphorus and algae concentrations caused by human activities but rather due to high color readings from water draining out of the surrounding wetlands, swamps and bogs.  It will be interesting to see if this draining of the surrounding wetlands has any lasting effects on these three water bodies.  The only way to tell if this does occur and lead to a continued decline in Rainbow Lake, Clear Ponds’ or Lake Kushaqua’s water quality and a drop in dissolved oxygen is to continue to monitor next year and in the years to come to see if the trend reverses itself 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.

Click here for the full report.