| Abstract/Description or Keywords |
The Columbia River watershed is located in the southeast corner of British Columbia. Water quality measurements for the Columbia River at Birchbank are from samples collected 10 km upstream from Trail, B.C.. The drainage area at this point is 102,852 km2, with the Rocky Mountains to the east and the Purcell Mountains to the west. The river flows in the Rocky Mountain Trench and is used for drinking water, irrigation and industry and supports populations of cutthroat, rainbow, bull, and eastern trout and whitefish. Cirque glaciers in the high Purcell and Rocky mountains drain to the Columbia River and the glacial silt imparts a gray, muddy colour to the river at times. This is alleviated by the time the water reaches Birchbank due to the settling provided behind the reservoirs created for electricity generation. The main influences on water quality at the Birchbank site include the Hugh Keenleyside, Mica and Revelstoke dams on the Columbia River upstream from Castlegar and the Libby and Brilliant dams on the Kootenay River. The pulp mill at Castlegar and treated municipal wastewater discharges from the Nelson-Castlegar area may also affect water quality. There are also non-point source discharges from agriculture, urban development, forestry, transportation and stream bank erosion. CONCLUSIONS: _ Several metals that exceeded guidelines on occasion had higher concentrations that correlated with high turbidity levels. At those times, metals were likely in particulate form and not biologically available. Such metals included aluminum, cadmium, chromium, copper, iron, and lead. It should be noted that data for a number of metals (copper, chromium, lead, nickel, zinc) prior to 1991 are questionable due to potential contamination from preservative vials in use at the time. These are included on the graphs for completeness, but where contamination exists it is readily apparent. _ There appear to be a number of declining trends through time in the Columbia River at Birchbank for aluminum, iron, phosphorus and lanthanum. The trends for aluminum, iron and phosphorus had been noted in an earlier report (Holms and Pommen, 1999), and possibly attributed in part to the sediment trapping effect of upstream dams and reservoirs; another potential reason cited for the decrease in phosphorus was waste abatement. The reasons for the apparent trend in lanthanum are not known at this time. There are also possible increasing trends for dissolved sulphate and total dissolved nitrogen. This latter trend is likely due to known filtration contamination in the laboratory beginning around 2004. All of the other possible trends noted above require statistical testing to confirm these visual assessments. _ Water quality in the Columbia River at Birchbank would be characterized as being good for both the protection of aquatic life and source waters used for drinking. This is likely due in large part to the settling out of particulate matter behind the upstream dams. There are relatively low fecal coliform levels and disinfection of all surface waters is required in British Columbia. RECOMMENDATIONS: We recommend monitoring be continued for the Columbia River at Birchbank since it serves as an upstream control station for the Columbia River at Waneta which is just above the International Boundary. Water quality indicators that are important for future monitoring are: _ flow, water temperature, specific conductivity, pH, turbidity, nutrients, total gas pressure and dissolved oxygen, _ appropriate forms of metals for comparison to their respective guidelines, and _ other variables related to drinking water such as colour. |
