Lake Pocotopaug Lake and Watershed Restoration Evaluation ...

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Table 17. Empirical Model Calculations using Lake Pocotopaug TP Range.MODELValueUsing 10ug/LValueUsing 20ug/LValueUsing 5 ug/LMean Chlorophyll (ug/L)Dillon and Rigler 1974 2.1 5.6 0.8Jones and Bachmann 1976 2.3 6.4 0.9Oglesby and Schaffner 1978 2.8 8.6 0.0Modified Vollenweider 1982 5.1 9.9 2.6Average 3.1 7.6 1.1"Maximum" Chlorophyll (ug/L)Modified Vollenweider (TP) 1982 14.4 29.7 6.9Vollenweider (CHL) 1982 8.6 22.5 2.7Modified Jones, Rast and Lee 1979 10.7 26.2 3.8Average 11.2 26.1 4.5Secchi Transparency (M)Oglesby and Schaffner 1978 (Avg) 3.9 2.3 6.7Modified Vollenweider 1982 (Max) 5.1 4.2 6.2SDT (m) SDT (m) SDT (m)Carlson (1977) with avg chl 3.57 1.93 7.44Frink and Norvell (1984) with avg chl 4.78 2.98 6.55Carlson (1977) with max chl 1.49 0.84 2.77Frink and Norvell (1984) with max chl 2.30 1.18 4.04Lake Pocotopaug Restoration Evaluation 82May 2002
8.0 PHOSPHORUS LOADINGThe loading of phosphorus to Lake Pocotopaug is critical to its ecological function andgeneral appearance. To clearly define inputs, a very large amount of sampling isneeded over an extended time period. As it is seldom possible to perform this level ofsampling, most studies combine a lower sampling frequency with modeling efforts toestimate the range of likely loading. This study has involved several in-lake samplingsand tributary samplings covering both wet and dry conditions. The phosphorus loadinganalysis presented here uses phosphorus literature values and concentrations recordedduring 2001. Total phosphorus concentrations are multiplied by the volume of eachinput to obtain an estimate of the total phosphorus load to Lake Pocotopaug.8.1 Loading SourcesA total of 30 dry weather and 45 wet weather samples were collected the 2001investigation. Sites included both tributaries and stormwater inputs. Not all stationswere sampled on all dates, as flow was minimal in some cases and extensive flowswashed away some of the passive stormwater samplers.Direct precipitation loading was calculated from a range of values of precipitation TPconcentration of 10-20 ug/L, based on studies of other southern New England lakes byENSR staff. The volume of water entering Lake Pocotopaug through precipitation wasmultiplied by the TP values. A value slightly lower than the average (simply as afunction of convenient rounding) was used as the “best estimate” for phosphorus loadingfrom precipitation (Table 18). Groundwater loading was estimated in a similar way (10-20 ug/L multiplied by volume of water entering Lake Pocotopaug), based on valuesobtained for other lakes by ENSR staff. An average was used as the “best estimate” forphosphorus loading from groundwater. Given the few septic systems in this largelysewered watershed, it can be reasonably expected that loading of phosphorus fromgroundwater will be small.Wet weather loading was calculated using median and mean TP values recorded during2001 (0.124 and 0.317 mg/L). The volume of water entering the lake during wet weatherwas multiplied by median and mean TP concentrations to obtain a wet weather loadingrange of 434 – 1110 kg/yr. The best estimate was calculated using the percent DP inthe TP samples, since it is likely that much of the phosphorus entering the lake is boundand unavailable, and much of it settles to the bottom (Table 18). Dry weatherphosphorus loading was calculated using the same methodology. Median and mean dryweather phosphorus values were 0.019 and 0.050 mg/L. Again, the best estimate wascalculated using the percent DP in the TP samples (Table 18).Lake Pocotopaug Restoration Evaluation 83May 2002
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LAKE POCOTOPAUGLAKE AND WATERSHEDRE
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11.3 Prevent algal blooms from occu
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LAYPERSON’S SYNOPSISLake Pocotopa
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The stocking of walleye in Lake Poc
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Lake Pocotopaug Restoration Evaluat
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Period Covered 1988• Pollution fr
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Recommendations included• Algacid
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Major EventDecember 1999 - Fish kil
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Table 5. Land Use from the CT DEP G
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Figure 4. Lake Pocotopaug Bathymetr
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Table 6. QA/QC on Water Quality Dat
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Soils - USDA at MAGIC UCONN Geograp
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Table 8. Water Quality Variables Me
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Phytoplankton samples were collecte
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where many measurements would have
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Figure 7. 2001 Temperature and Diss
Page 38 and 39: Table 10 continued. 2001 Lake Pocot
Page 40 and 41: phytoplankton biomass (Wetzel 1983)
Page 42 and 43: Figure 9. Annual June, July and Aug
Page 44 and 45: elow 7:1 occurred on September 22,
Page 46 and 47: Table 12. 2001 Dry and Wet Weather
Page 48 and 49: Table 12 continued. 2001 Dry and We
Page 56 and 57: were identified to genus and enumer
Page 58 and 59: Table 13 continued. 2001 Phytoplank
Page 68 and 69: Figure 10. 2001 Phytoplankton Bioma
Page 70 and 71: The late summer bloom of blue-green
Page 72 and 73: Table 15. 2001 Zooplankton DensityZ
Page 74 and 75: Table 16. 2001 Zooplankton BiomassZ
Page 76 and 77: 7.0 RELATIONSHIPS AND TRENDS7.1 Pre
Page 78 and 79: Figure 13. 1991-2001 Surface Water
Page 80 and 81: Figure 15. 2001 Surface and Mid-dep
Page 82 and 83: Figure 16. 1991-2001 Chlorophyll a
Page 84 and 85: Figure 18. 2001 Chlorophyll a vs. S
Page 86 and 87: Figure 20. 1991-2001 July and Augus
Page 90 and 91: Table 18. Total Phosphorus Loading
Page 92 and 93: Table 19. Wet Weather Loading Summa
Page 94 and 95: With the best possible treatment of
Page 96 and 97: water quality should focus on input
Page 98 and 99: 10.0 MANAGEMENT NEEDS AND OBJECTIVE
Page 100 and 101: 11.2 Reducing Total Phosphorus and
Page 102 and 103: undeveloped forest land, an opportu
Page 104 and 105: Figure 22. Buffer Strips for Pollut
Page 106 and 107: Figure 23. Catch Basin with Sump an
Page 108 and 109: early spring to capture what appear
Page 110 and 111: Figure 26. Infiltration Systems.Lak
Page 112 and 113: Figure 27. Constructed Treatment We
Page 114 and 115: Chemical TreatmentIn-stream chemica
Page 116 and 117: TABLE 21. MANAGEMENT OPTIONS FOR CO
Page 118 and 119: TABLE 21 continued. MANAGEMENT OPTI
Page 130 and 131: 12.0 ADDITIONAL DATA NEEDSManagemen
Page 132 and 133: 13.0 RECOMMENDED MANAGEMENT PROGRAM
Page 134 and 135: this point, but as a rough guide, a
Page 136 and 137: 14.0 REFERENCESAd Hoc Lake Advisory
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Scheuler T.R., P.A. Kumble, & M.A.
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Appendix B:Supplemental Tables and
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Appendix D:Educational MaterialsLak
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