BOSWORTH LAKE -- SNOHOMISH COUNTY: 1997

Lake Bosworth is located 2.3 miles south of Granite Falls. It is fed by two unnamed inlets, and drains northeast to the Pilchuck River.

Size (acres)                         105
Maximum Depth (feet)                  79
Mean Depth (feet)                     35
Lake Volume (acre-feet)             3675
Drainage Area (square miles)        1.41
Altitude (feet)                      563
Shoreline Length (miles)             2.0

Contour Map

Source of morphometric data: Water Supply Bulletins 42, 43, and 57.

VOLUNTEER-COLLECTED SECCHI DATA
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Date Temperature Water %Cloud Recent Secchi Lake
(Y/M/D) (C) (F) pH Color Cover Rain Wind (ft) Ht(in) Abbrev. Comments
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STATION 1
97/06/19 18.3 65.0 Pea-green 90 Heavy Calm 18.0 -13.0
97/07/02 18.9 66.0 Pea-green 25 Mod Calm 16.0 -12.0
97/07/16 20.0 68.0 Pea-green 50 Trace Light 17.0 -12.5 ON JULY 8 THERE WAS A MAN IN A WHITE BOAT DOING A
LAKE TEST. wHY? MAYBE HE WAS FROM THE COUNTY?!
97/07/30 22.2 72.0 Pea-green 25 None Light 16.0 -15.0
97/08/14 25.6 78.0 Undefined 1 None Calm 13.0 0.0 COLOR: PEA-SOUP GREEN / GREENISH BROWN
97/08/28 21.1 70.0 Pea-green 100 Mod Calm 12.0 -18.0
97/09/11 21.1 70.0 Grn-brown 100 Trace Calm 11.0 -19.0
97/09/28 Grn-brown 100 Heavy Breezy 13.5 -12.0
97/10/10 14.4 57.9 Pea-green 100 Heavy Light 16.0 -9.5
97/10/27 12.8 55.0 Pea-green 75 Mod Calm 20.0 -12.0
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LABORATORY RESULTS
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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)
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STATION 1
97/06/03 E 7
97/06/03 H 9
97/09/11 E 8 0.36 4.8
97/09/11 H 7 0.61
STATION 2
97/09/11 E 6 4.3
STATION 2
97/09/11 E 3.9
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E=epilimnion composite, H=hypolimnion composite. Remarks codes: U = Below detection limits; J = Estimate.

SUMMARY OF VOLUNTEER SURVEY

WATER QUALITY-----------------------------------------------------------------------
Overall water quality was good. The worst problems were reported as:
1. excessive aquatic plants 2. swimmer's itch 3. algae
Sources of actual or potential problems includes:

Were there days (and how many) when poor water quality impaired
Fishing - NO(0) Swimming - NO(0) Aesthetics - YES(140)
MANAGEMENT--------------------------------------------------------------------------
Did the lake receive chemical treatments this year? NO
Were fish stocked this year? YES
Any lake groups present (such as a lake association)? NO
Any lake management activities this year? NO
OTHER-------------------------------------------------------------------------------
How many homes/new homes are there on the lake shore?~ 113
Changes since last year? SOME CLEARING OF PROPERTY.

FIELD OBSERVATIONS OF ECOLOGY STAFF
6-3-97 The volunteer noticed peat material floating on the surface 3 weeks ago. The
lake was a mill pond years ago so the peat could have floated up from the bottom. Two
eagles spotted together for the 1st time since 1984. They were spotted a week ago.
An osprey was observed fishing. Blue-green algae was very abundant.

8-27-98 A few zooplankton observed in the surface samples. A turtle and osprey were
observed. There was heavy rain.

TROPHIC STATUS
Estimated Trophic State: Oligo-mesotrophic
Mean Trophic State Index (Secchi): 38 (Oligo-mesotrophic)
Mean Trophic State Index (Total Phosphorus): 32 (Oligotrophic)
Mean Trophic State Index (Chlorophyll a): 45 (Mesotrophic)

SUMMARY AND EXPLANATION OF TROPHIC STATE ASSESSMENT
Bosworth Lake has maintained its relative pristine nature through the years. TSI
values are favorable for an oligotrophic lake while DO concentrations and chlorophyll
TSI readings are more indicative of a mesotrophic lake, therefore, an assessment of
oligo-mesotrophic is appropriate.

COMMENTS FROM 92/05/15 AQUATIC PLANT SURVEY
Aquatic plants were surveyed at the public access and at one to three transects around
the lake. A thorough survey was not made and the list below may be incomplete.

AQUATIC PLANT LIST (This list may be from multiple years and sources.)Iris
pseudacorus (yellow flag)

Data collected and provided by Washington Department of Ecology's Lake Monitoring Program (Maggie Bell-McKinnon, phone 360-407-6124).

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