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Lake Osoyoos is located one mile north of Oroville. It is ten miles long and extends north into Canada. The total size of the lake is 5,729 acres; 3,693 acres lie in British Columbia, Canada, and 2,036 acres lie in the U.S. Lake Osoyoos is fed principally by the Okanogan River in Canada and drains south via the Okanogan River in the U.S. to the Columbia River.
Size (acres) 5800 Maximum Depth (feet) 208 Mean Depth (feet) 46 Lake Volume (acre-feet) 266800 Drainage Area (square miles) 3150.00 Altitude (feet) 911 Shoreline Length (miles) 29.7
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 97/06/02 18.9 66.0 Lt Green 0 Heavy Calm 14.5 168.7 97/06/16 21.1 70.0 Lt Green 10 Heavy Light 10.0 0.0 LAKE AT 913.68 FEET ABOVE SEA LEVEL 97/07/02 22.8 73.0 Lt Green 0 Light Calm 12.5 0.0 MILLFOIL SHOWING WASHED UP ON SHORE. WATER LEVEL AT 912'AND .48" ABOVE SEA LEVEL. 97/07/18 23.9 75.0 Lt Brown 0 Light Calm 11.5 0.0 MILFOIL GROWING. LOTS OF BOAT TRAFFIC AND TOURISTS. 97/08/03 25.0 77.0 Lt Green 0 None Calm 11.0 0.0 MILFOIL DEEP ON MY SHORELAND. WATER LEVEL WAS AT 912 FEET AND FOUR INCHES. 97/08/18 22.2 72.0 Lt Green 10 Trace Calm 16.0 0.0 WATER LEVEL WAS 911 FEET 9 INCHES. DAVE HALLOCK WAS WITH ME. 97/09/12 21.1 70.0 Lt Green 10 Mod Light 16.5 0.0 MISSED sEPT. 1 (VACATION). WATER LEVEL WAS 911 FEET 7 INCHES. 97/10/06 17.2 63.0 Lt Green 0 Trace Calm 10.0 0.0 LAKE WAS AT 911.16 FEET ABOVE SEA LEVEL. CAN'T EXPLAIN DROP TO 10' ON DISK. 97/10/20 14.4 57.9 Lt Brown 0 Trace Calm 9.0 0.0 LOTS OF BROWN ALGAE ON ROCKS + MANY OBJECTS IN THE WATER. ________________________________________________________________________________________________________________________
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 97/05/19 E 10 0.30 97/05/19 H 10 0.26 97/08/18 E 13 3.2 97/08/18 H 46 ________________________________________________________________________________________________________________________ E=epilimnion composite, H=hypolimnion composite. Remarks codes: U = Below detection limits; J = Estimate.
SUMMARY OF VOLUNTEER SURVEY WATER QUALITY----------------------------------------------------------------------- Overall water quality was excellent. The worst problems were reported as: 1. excessive aquatic plants 2. algae 3. suspended sediment Sources of actual or potential problems includes: SOME YEARS MILFOIL GROWTH IS VERY HEAVY. SEPTIC SYSTEMS ARE GETTING OLD AND PROBABLY FAILING. Were there days (and how many) when poor water quality impaired Fishing - NO(0) Swimming - NO(0) Aesthetics - NO(0) MANAGEMENT-------------------------------------------------------------------------- Did the lake receive chemical treatments this year? YES Were fish stocked this year? NO Any lake groups present (such as a lake association)? YES Any lake management activities this year? YES OTHER------------------------------------------------------------------------------- How many homes/new homes are there on the lake shore? 226 Changes since last year? A VERY EXCELLENT CAPMGROUND WAS BUILT ON THE EASTSIDE
FIELD OBSERVATIONS OF ECOLOGY STAFF According to volunteer, spring water levels were higher than they have been since 1974. State park was closed due to high water. At summer sampling, volunteer reported more milfoil than usual in some areas. H2S smell at 20M.
TROPHIC STATUS Estimated Trophic State: Mesotrophic Mean Trophic State Index (Secchi): 41 (Oligo-mesotrophic) Mean Trophic State Index (Total Phosphorus): 42 (Mesotrophic) Mean Trophic State Index (Chlorophyll a): 42 (Mesotrophic)
SUMMARY AND EXPLANATION OF TROPHIC STATE ASSESSMENT Although TSI values suggest an oligo-mesotrophic assessment, summertime hypolimnetic DO concentrations show a lake that is nearly anoxic in the hypolimnion. All factors considered, a mesotrophic assessment is most suited for Lake Osoyoos.
COMMENTS FROM 92/10/01 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.) Elodea canadensis (common elodea) Myriophyllum sp. (water-milfoil) Myriophyllum spicatum (Eurasian water-milfoil) Potamogeton crispus (curly leaf pondweed)
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