Water Quality: Long Term Trends 2018-06-12T21:18:47-04:00

Water Quality:  Long Term Trends

Since 1981, the Chocorua Lake Conservancy has partnered with the UNH Center for Freshwater Biology in the New Hampshire Lakes Lay Monitoring Program.  An analysis of long term trends undertaken in 2014 indicated that the water quality of Chocorua Lake has improved slightly.

2014 - 2000 to 2014 Phosphorus & Chlorophyll dataChlorophyll a concentrations, a measure of microscopic plant life within the lake, have decreased approximately 0.1 parts per billion (ppb) over the past thirty-two years of water quality monitoring; however the data do not reveal a statistically significant trend.  A closer examination of the data indicates that the chlorophyll a concentrations increased between 1982 and 1999, while data collected between 2000 and 2013 indicated a leveling off, or decrease.  The annual chlorophyll a concentrations in Chocorua Lake have stabilized since the Chocorua Lake Conservancy and partner organizations implemented storm water runoff control measures along Route 16 in the year 2000.

Water clarity has decreased approximately 50 centimeters over the past thirty-two years, although this is not a statistically significant trend.  A preliminary analysis of the interrelationship between water clarity measurements and precipitation (rainfall and snowfall) indicate years with elevated precipitation tend to coincide with shallower water clarity measurements relative to years with less rainfall.  Water quality is measured using a Secchi disk.

2014 - Long term Phosphorus & Water color dataTotal phosphorus concentrations have decreased slightly over the past fifteen years of sampling, but the relationship is not statistically significant. Phosphorus is the nutrient most responsible for microscopic plant growth.

Water color does not indicate a distinct trend over the past twenty‐six years of sampling. Preliminary analysis of the relationship between precipitation and color indicates weak correlation between rainfall and color; color concentrations tend to be higher during wet years relative to dry years.


For more about the life cycle of lakes, and what makes Chocorua an oligotrophic lake, see see the Fall/Winter 2015 CLC Newsletter.  For a history of the CLC’s water quality testing program in Chocorua Lake, see see the Spring/Summer 2015 CLC Newsletter.

Funding for the Chocorua Lake water quality monitoring program is provided by the Conservancy. The Chocorua Lake Conservancy has been participating in the New Hampshire Lakes Lay Monitoring Program since 1981.  The New Hampshire Lakes Lay Monitoring Program is jointly administered through the UNH Cooperative Extension Natural Resources Program Team and the Center for Freshwater Biology at the University of New Hampshire.

To support the Conservancy’s efforts to preserve the Chocorua Lake Basin and provide public lake access for visitors, please click HERE.