| Abstract/Description or Keywords |
The Fraser River basin is one of British Columbia's most valued ecosystems, draining one-quarter of the province. Its headwaters are located near Moose Lake in the Rocky Mountains. The northern part of the river follows a north-west path before heading south starting just north from Prince George. The Fraser River then flows 600 km before turning to the west, near Hope, B.C., and flowing in a south-westerly direction to the Pacific Ocean. The river has two major tributaries which affect its flow and water quality: the Nechako River which merges with the Fraser River at Prince George; and the Thompson River which flows into the Fraser River at Lytton, B.C., approximately 95 km north from Hope. These two tributaries contribute 41% of the total Fraser River flow at Hope: the Thompson River contributes 30% and the Nechako River contributes 11%. There are four long-term water quality monitoring sites on the Fraser River (Red Pass, Hansard, Marguerite, and Hope), as well as sites on both the Nechako and Thompson rivers. This report deals with the site on the Fraser River at Marguerite . Marguerite is in central B.C., roughly halfway between Quesnel and Williams Lake. Water quality at this site is affected by five upstream mills producing pulp and/or paper: three in Prince George and two in Quesnel. The designated water uses for this reach of the Fraser River are aquatic life, wildlife, drinking water (with partial treatment and disinfection), livestock, irrigation, and secondary-contact recreation (e.g., boating). This report assesses eighteen years of data from 1984 – 2004. CONCLUSIONS: • Flows are typical of interior rivers, with peaks occurring during the spring to early summer period and low flow taking place during the late autumn through winter periods. • Turbidity levels at this station seem to be increasing through time, and related metals (barium, cadmium, cobalt, chromium, manganese and zinc) also appear to be increasing. These apparent trends will be tested with more rigorous statistical approaches than we have used in this report. A similar trend in turbidity was apparent at the upstream Hansard station but not at the further upstream Red Pass reference station. These possible trends are not of environmental concern in this river. • Turbidity levels were high enough that if the water were to be considered as source water for drinking, that partial treatment would be required. This was reinforced by concentrations present of dissolved organic carbon, fecal coliforms, colour, • A number of metals exceed water quality guidelines, especially at times of high turbidity implying that the metal is in particulate form and not biologically available. These include aluminum, cadmium, chromium, cobalt, copper, lead, silver, and zinc. • Chloride concentrations have shown a marked decrease since early 1992, likely due to the elimination of chlorine dioxide as a bleaching compound at the pulp and paper mills. Similar decreases were not apparent upstream at Hansard where there would be no influences from pulp mills. • Extractable potassium seems to be increasing through time, although this may be due to laboratory methodology changes over the period of record. This apparent trend will be tested with more rigorous statistical approaches than we have used in this report. • Water temperatures vary seasonally as is to be expected, peaking during the hot summer months and on occasion exceeding guidelines for the protection of aquatic life. This is not a regular occurrence but could reduce the energy levels of salmon that might be migrating upstream during these periods. RECOMMENDATIONS: • We recommend monitoring be continued for the Fraser River at Marguerite to track the possible increases in variables that have been identified in this report. As well, either trivalent and hexavalent forms of chromium should be measured in the future, or alternately, guidelines be developed for total chromium values. Water quality indicators that are important for future monitoring are: • Flow because of its importance in interpreting many water quality indicators. • water temperature, specific conductivity, pH, turbidity, and dissolved oxygen, • appropriate forms of metals for comparison to their respective guidelines such as chromium where either trivalent and hexavalent forms of chromium need to be measured in the future, or guidelines be developed for total chromium values, and • other variables related to drinking water such as colour and dissolved organic carbon. |
