Lake Pocotopaug Lake and Watershed Restoration Evaluation ...

Suspended solids and turbidity concentrations were substantially higher in wet weather,indicating that sediment loading to Lake Pocotopaug is significant. WMC documented highsediment load and provided a detailed list of procedures with costs to reduce this load in their1995 report (Appendix C).pH was moderately to slightly acidic in all tributaries and storm drains. pH ranged from 5.7 to7.2 SU during dry and wet weather combined. Average, across all stations, was slightly lowerduring wet weather, likely due to acid precipitation. Alkalinity was slightly higher in wet weather(average 14 vs 16 mg/L in dry and wet conditions, respectively).Chloride, hardness and conductivity were slightly lower in wet weather; average chloride valueswere 32 to 20 mg/L (dry and wet, respectively), average hardness were 30 to 21 mg/L (dry andwet, respectively), and average conductivity were 154 and 128 mg/L (dry and wet, respectively).These lower values during wet conditions suggest a constant load from the watershed that isbeing diluted during precipitation.Nutrients, for the most part, were higher during wet weather than during dry conditions onaverage in 2001. Ammonium and TKN concentrations were generally higher duringprecipitation events. However, nitrate was lower on average. TKN was the only nitrogenvariable that was substantially different in dry verses wet weather in 2001 (average 0.27 and 2.0mg/L during dry and wet weather respectively). Total and dissolved phosphorus values weresignificantly higher (P< 0.005) during wet weather. Wet weather TP concentrations ranged from0.01 to 3.01 mg/L; DP wet weather concentrations ranged from 0.001 to 0.135 mg/L. Averagedry weather TP and DP concentrations were 0.050 and 0.013 mg/L. Average wet weather TPand TP concentrations were 0.317 and 0.035 mg/L, respectively.Dry weather metal concentrations were generally low. Concentrations increased for the mostpart during wet weather. Aluminum concentrations ranged from 0.06 to 15.7 mg/L. Cadmium,copper, lead and zinc exceed the State of Connecticut Water Quality Standards for AcuteToxicity to Freshwater Aquatic Life during wet weather conditions. Arsenic, chromium andnickel were below the state standards.6.3 In-Lake Biology6.3.1 PhytoplanktonThe phytoplankton of Lake Pocotopaug were sampled and analyzed monthly from April throughDecember 2001, with samples collected from two stations. From April through Septembersamples were collected as a composite of the epilimnetic waters (roughly the upper 20 ft), whiletwo discrete samples were collected near the surface and at the Secchi depth in Octoberthrough December. Samples were preserved in Lugol’s solution, concentrated by settling, andviewed in a Palmer Maloney counting chamber at 400x under phase optics. PhytoplanktonLake Pocotopaug Restoration Evaluation 49May 2002