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.

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