This report assesses the long-term water quality trends of the South Thompson River at Kamloops. The South Thompson River, in the Southern Interior of British Columbia, begins at the outlet of Little Shuswap Lake, and flows southwest and west for 60 km before it converges with the North Thompson River at the City of Kamloops. Water quality has been monitored on the South Thompson River at Kamloops, with a flow station near Chase. BC Environment began water quality monitoring at Kamloops in 1973. Five other related water quality monitoring stations within the Thompson River watershed are: the North Thompson River at North Kamloops, the Bonaparte River near mouth, the Thompson River at Spences Bridge, the Salmon River at Highway #1, and the Nicola River at Spences Bridge.
The plotted data were compared to the water quality objectives for the South Thompson River and to British Columbia's approved and working guidelines for water quality to see if any of the measurements had exceeded objectives or guidelines. Of special interest were water quality levels and trends that were deemed deleterious to sensitive water uses, including drinking water, aquatic life, wildlife, recreation, irrigation, and livestock watering.
The main conclusions of this assessment are:
· No environmentally significant trends in water quality were detected by visual appraisal of the data with the exception of suspended solids which is thought to be largely non-point source related such as from agriculture, forestry and residential development.
· The water was well buffered against acid inputs throughout the year, but yet quite soft for drinking water.
· The water was cool or cold enough throughout most of the year to be aesthetically pleasing for drinking, and usually warm enough during the summer months to permit water-contact recreation such as swimming.
· Turbidity and non-filterable residue levels were elevated during freshet when higher flows resulted in increased runoff and erosion, particularly from tributary streams. Remediation of non-filterable residue and turbidity sources and levels is needed.
· Fecal coliforms probably did not meet the water quality objective for the South Thompson River designed to protect raw drinking water for use after only disinfection, and the remediation of the sources of fecal contamination is probably needed.
· During freshet, elevated levels of aluminum and iron occurred. These levels may not have been of concern however, since they were due to the increased suspended sediment in the water, and thus were probably mostly biologically unavailable.
· During freshet, elevated levels of phosphorus occurred, but the phosphorus was largely in particulate form, and not readily available for algal growth.
Our main recommendations:
· Reduce sources and levels of fecal coliforms, non-filterable residue, and turbidity in the watershed. Continue monitoring at this site as the South Thompson River is important both as a water resource and as an aquatic habitat.
Figure 1. Map of the Thompson River Basin.