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1. Introduction

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The North Thompson River originates in British Columbia's Rocky Mountains approximately 30 km southwest from Valemount, and flows mostly south through Clearwater and McLure (Figures 1 and 2). Approximately 300 km in length, the North Thompson River joins the South Thompson River at Kamloops, becoming the Thompson River, a main tributary to the Fraser River. Important tributaries are Noble, Heffley and Jamieson creeks, as well as Barriere, Clearwater, Raft, Mad, and Blue rivers, located successively upstream from the sampling site on the North Thompson River at North Kamloops. The drainage area at this site is about 20,000 km2 (Environment Canada, 1991).

There were no significant industrial discharges (Mardon, 1996) or municipal discharges (Wong, 1996) to the North Thompson River. The Clearwater Sewage Treatment Plant (STP) discharges to the ground near the river. There are no known sources of metals and no active mines in this watershed. However, agriculture, urbanization and forestry impacted the watershed. These effects were more pronounced in the lower part of the river, downstream from McLure, due to the higher population. In terms of agriculture, one problem feedlot near Jamieson Creek closed and is now being used to grow ginseng. This eliminated the manure problem, but added a potential problem with fungicides (Grace, 1996). The Clearwater fish hatchery has temporarily closed, eliminating it as a source of nutrients and organics (Grace, 1996), but was purchased by the provincial fisheries and will be reopened for trout production to replace the Loon Lake hatchery.

Expansions as a result of urbanization, such as the Sun Peaks Resort (formerly Tod Mountain), also impacted water quality. The ski hill increased its operations, and developed several large subdivisions and a village core of condominiums and about a dozen hotels. Expansion is expected to continue for another 30-40 years, ultimately resulting in 20,000 beds in the alpine watershed of Louis Creek (Grace, 1996). As well, the Heffley Creek landfill was expanded, since the landfill at Paul Lake was closed down and replaced with a transfer station due to problem bears. Water quality impacts of the landfills were likely minimal due to the small amount of leachate produced in the arid climate (Grace, 1996). A segment of Kamloops called Westsyde, which was served by on-site septic tanks and tile fields, was sewered in 1993-94. Since then, a large subdivision and golf course complex was built on the banks near Westsyde, likely increasing erosion into the North Thompson (Grace, 1996).

Forestry also influenced water quality, and monitoring of these impacts commenced in the summer of 1996 on some North Thompson River tributaries (Laviolette, 1996). Analyses of these data were not yet available. A plywood mill at Heffley Creek discharged a small amount of condensate from the veneer dryers to a wetland that drains into the river. Sampling of the wetland discharge showed no detectable effect (Mardon, 1996).

Water quality was monitored at the North Thompson River at North Kamloops by BC Environment from 1987 to 1995 at site number 0600164 (Figure 2). Flow was monitored at McLure by Environment Canada at station number BC08LB064, and is plotted in Figure 3. The water quality variables are plotted in alphabetical order in Figures 4 to 49. Other long-term monitoring stations in the Thompson River watershed are: South Thompson River at Kamloops (Webber, 2000a), and Thompson River at Spences Bridge (Webber, 2000b).

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