Executive Summary

Rainbow Lake 2005

Adirondack Watershed Institute

This report presents the findings of the 2005 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 2005.   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 three years and in the eutrophic range in 1999, 2001 and 2003.  Rainbow Lake continues to show water quality improvement in all readings the last three years.  Rainbow Lake exhibited slightly lower chlorophyll a levels, slightly lower total phosphorus concentrations and slightly higher transparencies in 2005 than in 2004. This again points to water quality improvements in Rainbow Lake in 2005.

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 phosphorous, secchi disk transparency and chlorophyll a values every year going back to 1984. Clear Pond’s water quality  has degraded somewhat from an early mesotrophic lake to a mid range mesotrophic lake.  Clear Ponds total phosphorous yearly average has increased steadily during the last seven years from 10 - 12 micrograms/L to 17 - 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 4.0 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 slightly lower chlorophyll a levels, slightly higher total phosphorus concentrations and slightly higher transparencies in 2005 than in 2004. This again points to water degradation in Clear Pond due to rising total phosphorous readings in 2005.

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 2002.  From 2002 till the present day, with the exception of 2003, the deficit has diminished somewhat.  This again shows water quality in Rainbow Lake is improving over the 1990's.   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.  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 or continues to show improvements as in the last few years.

The Rainbow Lake Association should continue the present water quality monitoring program at least at the level sampled in 2005 during 2006.  The only way to tell if humans are still causing a continued decline in 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 trend does continue Clear Ponds’ water quality will continue to decline and human impacts should be looked at very closely.   It is also important in 2006 to continue to monitor the water quality of Rainbow Lake to see if recent improvements in water quality continue.  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 seven years we are beginning to build one of the better long term lake data sets in the Adirondack Park.  By continuing to add onto this data set, we are now able to look at some long term trends and know what type of management tools are needed for the future health of Rainbow Lake and Clear Pond.