Water Quality

Water quality testing and monitoring

Candlewood Lake Authority has conducted water quality testing and monitoring since 1983 from May through October.  Four sites on Candlewood are measured and an additional site on Squantz Pond.  The water analysis helps us understand and improve the Lake’s ecosystem and guides our conservation efforts to preserve Candlewood Lake.

At each measuring site, CLA conducts several different tests.  First, A probe is lowered into the water at one meter intervals to record readings of:

  • Water Temperature
  • Dissolved Oxygen
  • Conductivity
  • pH
  • Relative Blue Green Algae Concentrations
  • Chlorophyll-a

Secondly, a Secchi disk- a black and white disk - is lowered into the water until it is no longer visible. The depth of the disk is recorded and to measure water clarity in the lake. High water clarity is typically an indicator of better water quality. When clarity is lower, there might be higher levels of particulate matter like soil and other solids)in the water, or it can be an indication of increased algae in the water, causing the water to appear green and less clear.

Finally, multiple water samples are collected for laboratory analysis using a Van Dorn Bottle, a specialized instrument that captures water at specific depths. Samples are taken from three depths (the surface, bottom, and “middle” layer) at each site. The lab will then test for nutrients: including Phosphorus and Nitrogen, Ions including Calcium, Potassium, and Sodium and Chlorophyll-a. The nutrients are key raw materials for algae, and can indicate how much the algae population can grow and reproduce this year. The ions can indicate how “salty” the water is, which can impact fish and plant populations in the lake. Finally, Chl-a is a way to measure how much algae is in the lake, which makes the water appear greener and less pleasant.

Blue-Green Algae Health Risks