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1. Introduction

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The Bonaparte River is a scenic river, originating in the British Columbia's southern interior near Bridge Lake. It flows southwest toward Clinton (Figure 1), south through the Town of Cache Creek, and then joins the Thompson River north of Ashcroft. Important tributaries to the river are Clinton Creek, which flows east and joins the Bonaparte River east of Clinton, and Loon Creek, which flows southwest and joins the Bonaparte River downstream from the Clinton Creek confluence. Other tributaries are Hat and Cache creeks, both located downstream from Loon Creek. The drainage area of the Bonaparte River below Cache Creek is 5 020 km2 (Environment Canada, 1991).

The Bonaparte watershed is influenced by agriculture, urbanisation and forestry. Ranching continues to be of importance, but a significant change to the agriculture industry has been the introduction of ginseng farming (Grace, 1996). No potential impacts of increased ginseng farming, such as frequent fungicide usage, have been identified to date (Grace, 1996). There are two sewage treatment plants (STP) within the Bonaparte River watershed, one downstream from the Town of Clinton which discharges into Clinton Creek, and a second plant downstream from the Town of Cache Creek, which discharges into the Bonaparte River. An ultra-violet disinfection system has been operational at the Village of Cache Creek STP since November 5, 1990, eliminating residual chlorine discharge into the river (Wong, 1996). Three landfill sites are also located in the watershed. Wastech Services Limited, near Cache Creek, is one of the largest landfills in British Columbia, handling approximately 500 000 tonnes/year from Greater Vancouver. This site replaces the refuse and septic tank sludge disposal site near Ashcroft, which was decommissioned in 1989 (Wong, 1996). A smaller landfill is located near Clinton, but the impacts of both operational landfills were considered minimal due to the arid climate, and the subsequent small amount of leachate produced (Grace, 1996; Swain, 1986).

Water quality was monitored at the Bonaparte River near the mouth by BC Environment from 1985 to 1995. Chlorophyll-a was monitored since 1978. The data are stored on the province's EMS data base under site number 0600329. Flow was monitored below Cache Creek by Environment Canada at station number BC08LF002, and is plotted in Figure 2. The water quality variables are plotted in alphabetical order in Figures 3 to 48. There are no other long-term monitoring stations in this watershed, but other long-term sites in this region include: South Thompson River at Kamloops (Webber, 1997a), North Thompson River at North Kamloops Webber, 1997b), and Thompson River at Spences Bridge (Webber, 1997c).

A number of water quality assessments have been conducted in past years. Loon and Clinton Creek have been reported to have had fecal coliform levels consistently in exceedence of objectives (Swain, 1986 and Ministry of Environment, Lands and Parks, 1996). High levels of suspended solids, turbidity and algae growth have also been noted for Clinton Creek (Ministry of Environment, Lands and Parks, 1996). Variables which have exceeded criteria in the Bonaparte River were fecal coliforms, and suspended solids (Swain, 1986), and turbidity and algae (Ministry of Environment, Lands and Parks, 1996). Naturally high levels of copper, iron and lead have also been observed in this river (Swain, 1986).

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