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Size (acres) 190 Maximum Depth (feet) 19 Mean Depth (feet) 13 Lake Volume (acre-feet) 2470 Drainage Area (square miles) 3.77 Altitude (feet) 154 Shoreline Length (miles) 4.6
Source of morphometric data: Water Supply Bulletins 42, 43, and 57.
VOLUNTEER-COLLECTED SECCHI DATA ________________________________________________________________________________________________________________________ Date Temperature Water %Cloud Recent Secchi Lake (Y/M/D) (C) (F) pH Color Cover Rain Wind (ft) Ht(in) Abbrev. Comments ________________________________________________________________________________________________________________________ STATION 1 96/06/06 Lt Green 50 Trace Light 8.5 0.0 ________________________________________________________________________________________________________________________
LABORATORY RESULTS ________________________________________________________________________________________________________________________ Total Total Fecal Col. Bacteria Turb- Suspended Solids Phosphorus Nitrogen Chlorophyll (colonies/100 mL) idity Total Non-Volatile Color Date Strata (ug/L) (mg/L) (ug/L) Site 1 Site 2 (NTU) (mg/L) (mg/L) (Pt-Co) ________________________________________________________________________________________________________________________ STATION 1 96/06/06 E 21 0.73 7.3 96/06/06 H 31 1.55 96/09/01 E 21 0.60 6.8 96/09/01 H 57 0.56 ________________________________________________________________________________________________________________________ E=epilimnion composite, H=hypolimnion composite. Remarks codes: U = Below detection limits; J = Estimate.
SUMMARY OF VOLUNTEER SURVEY There was no survey response for 1996. FIELD OBSERVATIONS OF ECOLOGY STAFF The volunteer did not take any Secchi readings from this lake. The shoreline was 90% naturally vegetated. Observed macrophytes include: Iris pseudacorus, Potamogeton amplifolius, and Nymphaea odorata, and Vallisneria americana. There was a large Chironomid hatch recently as many exuvia were observed on the surface.
TROPHIC STATUS Estimated Trophic State: Meso-eutrophic Mean Trophic State Index (Secchi): 41N* (Oligo-mesotrophic) Mean Trophic State Index (Total Phosphorus): 48 (Meso-eutrophic) Mean Trophic State Index (Chlorophyll a): 50 (Meso-eutrophic) *The calculated TSI is an estimate. The Secchi disk hit bottom (B), entered the weeds (W), or there were too few valid readings (N), or the calculation was based on qualified data (J), or TSIP was based on spring data (S).
SUMMARY AND EXPLANATION OF TROPHIC STATE ASSESSMENT Pattison Lake (South Arm) is classified as meso-eutrophic. Secchi readings may suggest a less eutrophic classification but blue-green algae predominance sometimes increases Secchi depth which may be the case here. Phosphorus and chlorophyll TSIs, along with macrophyte abundance and hypolimnetic dissolved oxygen depletion, may be more indicative of the meso-eutrophic classification.
AQUATIC PLANT LIST (This list may be from multiple years and sources.) Ceratophyllum demersum (Coontail; hornwort) Elodea canadensis (common elodea) Nuphar lutea (yellow water-lily) Nymphaea odorata (fragrant waterlily) Potamogeton amplifolius (large-leaf pondweed) Potamogeton crispus (curly leaf pondweed) Potamogeton praelongus (whitestem pondweed)
Data collected and provided by Washington Department of Ecology's Lake Monitoring Program (Maggie Bell-McKinnon, phone 360- 407-6124).
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