Executive Summary

Rainbow Lake 2009

Adirondack Watershed Institute

This report presents the findings of the 2009 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 three main stations, one each on Rainbow Lake, Clear Pond and Lake Kushaqua, once per month from June through August 2009.   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.

In all three lakes, it appears that there has been little change in trophic status since the mid – 1980’s.  Rainbow Lake appears to be a mesotrophic lake in terms of total phosphorus and secchi disk transparency every year going back to 1984.  Rainbow Lake has had chlorophyll a values in the mesotrophic range the last five years and in the eutrophic range in 1999, 2001, 2003.  Rainbow Lake showed water quality improvement in all readings from 2003 – 2006 and 2007 was equal to 2006.  Rainbow Lake showed poorer water quality in 2008 and 2009 than in the previous five years.  Rainbow Lake exhibited higher total phosphorus concentrations, slightly higher chlorophyll a levels, and slightly lower transparencies in 2008 and 2009.  This poorer water quality in 2008 and 2009 could be due to weather conditions and the very wet late spring and summer we experienced in the Adirondack Park the last two years.   It could also be due to increased human activity such as new construction, failing septic systems, lawn fertilization and improper landscaping.

Clear Pond, at first glance appears to have changed very little in trophic status since the mid – 1980s.  Clear Pond appears to be a mesotrophic lake in terms of total phosphorus, secchi disk transparency and chlorophyll a values every year going back to 1984.  Clear Pond’s water quality has degraded somewhat from the early mesotrophic lake to a mid range mesotrophic lake from 1997 to 2006.  Clear Ponds total phosphorus yearly average increased steadily during this time period from 10 – 12 micrograms/L to 16 – 19 micrograms/L.  At the same time, Clear Pond’s secchi disk transparency had fallen from an average of 4.7 meters to an average of 3.0 meters and its’ chlorophyll a values have risen from an average of 2 – 3 micrograms/L to an average of 5 – 6 micrograms/L.

Clear Pond exhibited improved water quality in 2007 for the first time in a while.  2008 and 2009 saw Clear Pond’s water quality return to the declining health we had seen from 1997 – 2006.  Clear Pond had higher chlorophyll a levels, significantly higher total phosphorus concentrations and lower transparencies in 2008 and 2009.  The total phosphorous concentrations in 2008 and 2009 were the highest we have seen over the course of this study and the Secchi disk transparencies were also some of the lowest we have ever seen.  This poorer water quality in 2008 and 2009 could be due to weather conditions and the very wet late spring and summer we experienced in the Adirondack Park the last two years.   It could also be due to increased human activity such as new construction, failing septic systems, lawn fertilization and improper landscaping.

Lake Kushaqua appears to be a mesotrophic lake in terms of total phosphorus and secchi disk transparency in 1984, 2000 and 2009.  Lake Kushaqua showed water quality improvement in all readings from 1984 to 2000 and a water quality in between during 2009.

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 2003.  From 2003 - 2005, the deficit had remained constant.  During the last four summers, 2006 – 2009, this oxygen deficit has been worse.  Such oxygen deficits are common in lakes that experience cultural eutrophication, or in other words, impacts from the surrounding human populations or surrounding land use.  These deficits usually occur when there are nutrients leeching into a lake by some human activity such as farming, forestry logging practices, road construction, new home construction, or failing old septic systems.  This deficit could be caused by human impacts around Rainbow Lake form 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 and may still be impacted the lake today.  The only way to tell if humans are still causing a continued decline in Rainbow Lakes’ water quality and drop in dissolved oxygen is to continue to monitor next year and in the years to come to see if the trend reverses itself, remains constant or shows improvements.

The Rainbow Lake Association should continue the present water quality monitoring program at least at the level sampled in 2009 with the addition of Lake Kushaqua.  The only way to tell if humans or weather are causing a continued decline in Rainbow Lake and Clear Ponds’ water quality and 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.  If this negative water quality trend does continue for both bodies of water, no matter what the weather conditions are, human impacts should be looked at very closely.  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 ten years we now have one of the better long term lake data sets in the Adirondack Park.   Finally, by adding Lake Kushaqua, we can begin to build on the very limited data set that presently exists for that lake as well.