Executive Summary

Rainbow Lake 2002

Adirondack Watershed Institute

This report presents the findings of the 2002-monitoring program for the Rainbow Lakes (Rainbow Lake, Clear Pond and Loon 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 three main stations, one each on Rainbow Lake and Clear Pond, once per month from June through August 2002.  A third station on Loon Pond was sampled during July and August only.  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.

Both Rainbow Lake and Clear Pond continue to be mesotrophic, while Loon Pond is dystrophic. Water quality conditions in Adirondack lakes & ponds were dominated by the weather again during 2002.  Although the weather averages for this year through this time seem to indicate a more “normal” year (one with ~38 inches of precipitation and ~42oF for the average temperature), the precipitation especially varied from the norm.  Of the 34.01 inches of precipitation received thus far, it all came during 70 days.  This indicates a “normal” amount of water entering the system, but in short, heavy bursts.  These bursts were not evenly spaced out throughout the year either.  The beginning of the summer (May and June) received 11.45 inches of precipitation.  The remainder the summer, however, exhibited quite hot and dry conditions.  These later summer conditions are similar to drought-like conditions experienced in 1999 and 2001, which affected the lakes as such.  Late summer conditions of low rainfall meant less drainage from the land, less dilution and lower acidic inputs in streams, lakes and ponds; while earlier conditions would show just the opposite. As a result, we generally observed the following in our study lakes: higher pH and alkalinity values; higher color, total phosphorus and chlorophyll a values, and lower transparency.   Both Rainbow Lake and Clear Pond seemed to closely follow this trend, while Loon Pond exhibited quite different water quality characteristics.

We now have a good historical record of dissolve oxygen profiles for Rainbow Lake dating back to 1954.  We can use theses profiles for comparative purposes and we can draw some conclusions from almost fifty years worth of historical data.  The historical dissolved oxygen data does show that the oxygen deficit in Rainbow Lake began to show itself in July by 1984.  This deficit has intensified during the 1990's and has become worse every year over the last five years. The deficit has rebounded a little this summer, but not enough to definitely conclude that the lake is “healing” itself and that the human impacts have declined.  This deficit could be caused by human impacts around Rainbow Lake from the 1960's, 1970's, and 1980’s or up to present day.  Overall, the data does suggest that humans have definitely influenced Rainbow Lakes’ water quality 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 the years to come to see if the trend reverses itself.  If this trend does continue Rainbow Lakes’ water quality will continue to decline and human impacts should be looked at very closely.