Executive Summary Rainbow Lake 2010 Adirondack Watershed Institute
This report presents the findings of the 2010 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 2010, near the deepest
portion of each lake. Lake Kushaqua was not sampled in June 2010 due to extremely high
water levels that made it impossible to get the boat under the bridge at the far end of
Rainbow 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.
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 eight 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 but 2010 was one
of the best years for water quality for Rainbow Lake. Rainbow Lakes’ water quality for
2010 showed the second best average Secchi disk transparency for the period of study
and the lowest average chlorophyll-a readings and the fourth lowest total phosphorous
average. This improved water quality in 2010 could be due to weather conditions and the
very wet summer we experienced in the Adirondack Park. This excessive rain could
have helped dilute out total phosphorous levels and helped lower chlorophyll-a levels and
improved Secchi disk transparency.
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 midrange
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. Clear Ponds’ water quality for 2010 showed an improved Secchi disk
transparency to about average for the period of study and the lowest average chlorophylla
readings since 2001 and the total phosphorous was also about average. This improved
water quality in 2010, could like Rainbow Lake, be due to weather conditions and the
very wet summer we experienced in the Adirondack Park. The improvements for
Rainbow Lake were much more pronounced than for Clear Pond.
Lake Kushaqua appears to be a mesotrophic lake in terms of total phosphorus,
chlorophyll-a and Secchi disk transparency over the period of record. Lake Kushaqua
showed water quality improvement in all readings from 1984 to 2000 and this
improvement continued in 2010. Lake Kushaqua’s water quality for 2010 showed the
best average Secchi disk transparency for the period of study and the lowest average
chlorophyll-a readings and total phosphorous average readings. This improved water
quality in 2010 could be due to weather conditions and the very wet summer we
experienced in the Adirondack Park. This excessive rain could have helped dilute out
total phosphorous levels and helped lower chlorophyll-a levels and improved Secchi disk
transparency.
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 previous four summers, 2006 – 2009, this oxygen deficit has
been worse. During 2010, this oxygen deficit was slightly less. 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 2010. The only way to tell if humans or weather
are causing a continued decline in Rainbow Lake, Clear Ponds’or Lake Kushaquas’ 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. If this
negative water quality trend does continue for Rainbow and especially Clear Pond, 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 fourteen 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.