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Horseshoe Lake is located on the Cowlitz-Clark County line adjacent to the town of Woodland. It was formed when US 99 (now I-5) was built in 1940, isolating a bend in the Lewis River. The acreage of the lake varies during flood seasons. Horeshoe Lake drains to the North Fork of the Lewis River.
Size (acres) 85 Maximum Depth (feet) 16 Mean Depth (feet) 6 Lake Volume (acre-feet) 510 Drainage Area (square miles) 0.41 Altitude (feet) 20 Shoreline Length (miles) 3.0
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 95/05/29 Lt Brown 0 6.5 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 95/05/29 E 24 0.23 7.7 5 2 2.5 95/05/29 H 95/09/14 E 41 0.26 11.9 65 6 95/09/14 H ________________________________________________________________________________________________________________________ E=epilimnion composite, H=hypolimnion composite. Remarks codes: U = Below detection limits; J = Estimate.
SUMMARY OF VOLUNTEER SURVEY There was no survey response for 1995. FIELD OBSERVATIONS OF ECOLOGY STAFF The lake apparently is aerated via the Lewis River. The algal flora is apparently dominated by green algae as no visible blue-green algal cells were observed.
TROPHIC STATUS Estimated Trophic State: Eutrophic Mean Trophic State Index (Secchi): 54N* (Eutrophic) Mean Trophic State Index (Total Phosphorus): 58 (Eutrophic) Mean Trophic State Index (Chlorophyll a): 53 (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 Horseshoe Lake is a shallow oxbow lake. High nutrients contribute to the high chlorophyll concentrations and shallow Secchi depths. This lake is classified as eutrophic.
Data collected and provided by Washington Department of Ecology's Lake Monitoring Program (Maggie Bell-McKinnon, phone 360-407-6124).
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Copyright © Washington State Department of Ecology. See http://www.ecy.wa.gov/copyright.html.
