Gravelly Lake is located 0.5 mile northwest of Ponders, between American and Steilacoom Lakes. It has no surface inlets, and seeps to Puget Sound. Although Gravelly Lake is listed as a public lake in Chapter 173-20 WAC, there is no public boat access on the lake.
Size (acres) 160 Maximum Depth (feet) 55 Mean Depth (feet) 38 Lake Volume (acre-feet) 6080 Drainage Area (square miles) 0.66 Altitude (feet) 220 Shoreline Length (miles) 2.1
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 97/07/20 22.8 73.0 Clear 0 None Light 30.0 12.0 LAKE TREATED 7/17. SLIGHT WAVE ACTION FROM BOATS. 97/08/11 24.4 75.9 Clear 0 None Light 29.0 18.0 97/09/05 22.2 72.0 Undefined 50 None 30.0 0.0 WATER WAS AQUA-MARINE. 97/09/05 22.2 72.0 50 30.0 0.0 STRONG H2S ON BOTTOM. WATER LEVEL DOWN 3' FROM SPRING ________________________________________________________________________________________________________________________
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 97/06/19 E 8 0.71 97/06/19 H 36 1.33 97/09/05 E 4 0.42 2.6 97/09/05 H 125 1.41 ________________________________________________________________________________________________________________________ E=epilimnion composite, H=hypolimnion composite. Remarks codes: U = Below detection limits; J = Estimate.
SUMMARY OF VOLUNTEER SURVEY There was no survey response for 1997. FIELD OBSERVATIONS OF ECOLOGY STAFF 9-5-97 Strong H2S odor from the bottom hypolimnion sample. Water level down 3' from the spring.
TROPHIC STATUS Estimated Trophic State: Oligo-mesotrophic Mean Trophic State Index (Secchi): 28N* (Oligotrophic) Mean Trophic State Index (Total Phosphorus): 25 (Oligotrophic) Mean Trophic State Index (Chlorophyll a): 40 (Oligo-mesotrophic) *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 Gravelly Lake is a lake that has undergone copper sulfate applications in the past. With the low phosphorus concentrations, you would expect a relatively insignificant algal population yet TSI values for chlorophyll remain high compared to values for phosphorus and Secchi. TSI values for Secchi and phosphorus suggest an ultra-oligotrophic lake yet hypolimnetic DO concentrations and H2S presence along with the elevated chlorophyll concentrations support an oligo-mesotrophic assessment.
Data collected and provided by Washington Department of Ecology's Lake Monitoring Program (Maggie Bell-McKinnon, phone 360-407-6124).
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