Executive Summary

Rainbow Lake 2006

Adirondack Watershed Institute

This report presents the findings of the 2006 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 2006.   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 continues to show water quality improvement in all readings the last four years.  Rainbow Lake exhibited slightly higher chlorophyll a levels, slightly lower total phosphorus concentrations and the same transparencies in 2006 as in 2005.  This again points to water quality improvements in Rainbow Lake in 2006.

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 slightly higher chlorophyll a levels, slightly lower total phosphorus concentrations and slightly lower transparencies in 2006 than in 2005.  This again points to water degradation in Clear Pond due to rising phosphorus readings in the last eight years.

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.  Form 2003 till present day, the deficit has remained constant.  This again shows water quality in Rainbow Lake is improving over the 1990’s.  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.  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 2006 during 2007.  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 2007 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 eight years we are beginning to build one of the better long term lake data sets in the Adirondack Park.  By continuing to add on to 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.