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Lake Whatcom Tributary Monitoring – Phase II Summary

Whatcom County Department of Public Works. Lake Whatcom Tributary Monitoring – Phase II Summary. April 26 | 2013. Lake Whatcom Tributary Monitoring: Phase II Summary. April 26, 2013. Agenda. Project Background Phase I & II Monitoring Summary Discussion. Background.

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Lake Whatcom Tributary Monitoring – Phase II Summary

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  1. Whatcom County Department of Public Works Lake Whatcom Tributary Monitoring – Phase II Summary April 26 | 2013

  2. Lake Whatcom Tributary Monitoring:Phase II Summary April 26, 2013

  3. Agenda • Project Background • Phase I & II Monitoring Summary • Discussion Brown and Caldwell

  4. Background • Lake Whatcom DO levels have declined due to elevated P • Since 2007, various monitoring efforts have taken place • In 2008, Ecology issued report recommending TMDLs for P inputs to the lake from 22 principal tributaries (subwatersheds) • Five of these sub-watersheds (Agate Bay, North Shore, Blue Canyon, South Bay and Strawberry) encompass more than one stream system. • Ten of these sub-watersheds have had routine monitoring or special studies conducted by various entities over the past decades. Brown and Caldwell

  5. Phase I Activities • Collected stormflow and bimonthly (mostly baseflow) samples for the nine main tributaries during 2007-2008. • Data sondes collected continuous turbidity • Evaluated correlations between TP and turbidity, TSS, and SRP Brown and Caldwell

  6. Phase I Monitoring Locations9 tributary subbasins (shaded areas) Brown and Caldwell

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  8. Phase I Monitoring Summary Brown and Caldwell

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  13. Phase I Findings • Significant correlations for TP & TSS & turbidity • HSPF modeling suggested model may underestimate TP from Austin, Olsen and Smith • Maybe due to lack of storm data for model calibration • Recommended sampling new and existing locations, and collecting winter stormflow samples to address key gaps and to help identify why model under-predicted P. Brown and Caldwell

  14. Phase II Plan • Sample numerous tribs with little or no existing data • Ecology had used data from 9 tribs to represent >15 unmonitored tribs • Measure wet weather P concentrations in tributaries • 9 Phase I tributaries • 15 additional tributaries with little or no previous monitoring • Up to six events at each location (144 total) • Rotating panel of three groups of sampling locations Brown and Caldwell

  15. Phase II Monitoring Locations15 tributary subbasin (shaded areas) & Panel Rotations (South, Southeast, and Northeast) Brown and Caldwell

  16. Phase II Status • Sampled 28 locations during 3 to 5 stormflow events (134 total) • Only three storms >1”, however Brown and Caldwell

  17. Phase II Subbasin Panel Details Brown and Caldwell

  18. Land Use Summaries for Phase II Areas Brown and Caldwell

  19. Percentages per WRIA subbasinby land use category Source: WDOE, Volume 2. Water Quality Improvement Report and Implementation Strategy. ( February 2013) Brown and Caldwell

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  26. Regression Analysis for select storm dates - Total P vs. Continuous and Grab Turbidity Brown and Caldwell

  27. Regression Analysis for select storm dates - Total P vs. Continuous and Grab Turbidity Brown and Caldwell

  28. Phase II Findings • Several new Phase II sites indicate elevated levels of TP (e.g., Coronado, Academy, Eagle Ridge, Donovan • Most TP is in Austin, Olsen, and Smith creeks is in particulate form. • TDP and SRP concentrations consistently similar, indicating that dissolved P predominately in SRP form. • SRP showed much less response to stormflow hydrographs compared with TP • TP and TSS showed strong correlations, suggesting that most of the TP is associated with particulates suspended in the water column Brown and Caldwell

  29. Phase II Findings, continued • Correlations between TP and continuous turbidity • Strong relationships during large storms • Weaker during smaller storms and baseflow, when turbidity and TSS were low • Silver Beach, Smith, Olsen showed best correlations • Anderson & Austin did not show good correlations • Perhaps due to Mirror Lake diversion (Anderson) • Perhaps due to low concentrations during storm events (Austin) • Most sampling events had total precipitation of 0.5 inches or less during sampling. Brown and Caldwell

  30. Discussion • Drop TDP? • Adjust sampling criteria? • Adjust locations? • HSPF modeling? • TMDL implementation support? Brown and Caldwell

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