| Abstract/Description or Keywords |
The Pend d’Oreille River accounts for 43% of the drainage area of the Columbia River as it enters the USA downstream from Waneta. It drains 65,300 km2 in the USA before entering B.C., where it drains an additional 1600 km2 before joining the Columbia River at Waneta about 22 km downstream. The Pend d’Oreille River in B.C. is dominated by hydroelectric facilities, with the Boundary Dam at the Canada-US border, the Waneta Dam just upstream from the Columbia River, and the Seven Mile Dam midway between the two. The three dams are barriers to migration to all fish. The river provides habitat for a wide variety of fish species, including sports fish such as bull trout, rainbow trout, brook trout, mountain whitefish, and Westslope (Yellowstone) cutthroat trout. Minor quantities of water are licensed for irrigation and domestic use. Other potential influences on water quality are mines (both active and closed), forestry, and agriculture. Some metals concentrations exceed guidelines on occasion during high flow/high turbidity periods (spring runoff/snowmelt). Elevated turbidity levels are likely natural, although they may be increased by past and present upstream activities. It is unlikely that aquatic life would be impacted by these short-term turbidity-driven metal exceedances. CONCLUSIONS: • Turbidity levels and specific conductivity fluctuate throughout the year in response to flow conditions. Turbidity increases during freshet periods when runoff carries solids from the land surface. Specific conductivity is generally at its highest when flows are low and the influence of ground waters that are harder than the surface water has most influence on water quality. • Water temperatures (and likely dissolved oxygen concentrations but these have not been measured) fluctuate throughout the year, with highest water temperatures occurring during the warmer summer months as would be expected. This is a period when we would expect the lowest dissolved oxygen concentrations because warmer water has a lesser capability to hold dissolved oxygen than colder water. • The data indicate that several metals that occasionally have values that exceed guidelines to protect aquatic life are associated with high concentrations of particulate matter. This means that the metals are likely in particulate form and are not biologically available and would be removed with treatment of this source water when used for drinking. • Fecal coliforms were considerably less than the guideline for source waters used for drinking that are not treated other than by disinfection. • One true colour value was associated with a high turbidity level, and this would be removed by treatment used to remove solids when the water is used as a source for drinking. Colour is an aesthetic concern and not a health issue per se. • Water temperature frequently exceeded the guideline to protect aquatic life during summer periods, but the margin above the guideline was small. • Analytical detection limits used for many metals has improved considerably in the period from 2003-2006. This has resulted in fewer values exceeding guidelines during that period. This relates to the fact that many of the former high values may have been “false positives” which is common when values are close to the detection limit. The new lower detection limits help to avoid such problems and allow us to present a more accurate picture of water quality. • There did appear to some long-term trends of increasing values through the period of record at this station for the following variables although none were environmentally significant: boron, chloride, and magnesium. Each of these needs to be verified by a statistical analysis. • There did appear to some long-term trends of decreasing values through the period of record at this station for the following variables although none were environmentally significant: antimony, lithium, rubidium, silicon, sulphate, specific conductivity, thallium, and uranium. Each of these needs to be verified by a statistical analysis. RECOMMENDATIONS: We recommend monitoring be continued for the Pend d’Oreille River at Waneta since it serves as an upstream station for the lower Columbia River site. Water quality indicators that are important for future monitoring are: • flow, water temperature, specific conductivity, pH, turbidity, nutrients, and dissolved oxygen, • appropriate forms of metals for comparison to their respective guidelines, and • other variables related to drinking water such as colour. |
