Executive Summary

Rainbow Lake 2008

Adirondack Watershed Institute

This report presents the findings of the 2008 monitoring program for the Rainbow Lakes (Rainbow Lake and Clear Pond). 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 two main stations, one each on Rainbow Lake and Clear Pond, once per month from June through August 2008.   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 both lakes, it appears that there has been little change in trophic status since the mid-1980s. Rainbow Lake appears to be a mesotrophic lake in terms of total phosphorous and secchi disk transparency every year going back to 1984. Rainbow Lake has had chlorophyll a values in the mesotrophic range the last four years and in the eutrophic range in 1999, 2001 and 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 than in the previous five years.  Rainbow Lake exhibited higher total phosphorus concentrations, slightly higher chlorophyll a levels, and slightly lower transparencies in 2008.  I feel this poorer water quality in 2008 was due to weather conditions and the very wet late spring and summer we experienced in the Adirondack Park in 2008.

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.  Clear Ponds total phosphorus yearly average has increased steadily during the last eight years from 10 – 12 micrograms/L to 16 – 18 micrograms/L.  At the same time, Clear Pond’s secchi disk transparency has fallen from an average of 4.7 meters to an average of 3.5 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 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 than in 2007.  The total phosphorous concentrations in 2008 were the highest we have seen over the course of this study and the Secchi disk transparencies were only lower in 2002.

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 three summers, 2006 – 2008, this oxygen deficit has begun to worsen again.  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 2008 during 2009.  The only way to tell if humans are still 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.  If this negative water quality trend does continue for both bodies of water 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 are building one of the better long term lake data sets in the Adirondack Park.

Finally one last note, by performing this annual water quality study of Rainbow Lake and Clear Pond this is very important for any future grants that may be obtained at the State or national level.  Any grant application, even if for invasive species, is much stronger and shows the granting body that the people that live around Rainbow Lake and Clear Pond are organized and have a management plan and a clear focus if they have this type of water quality information collected on an annual basis.