| Abstract/Description or Keywords |
The Moyie River watershed is located in the southeast corner of British Columbia. Its headwaters are in the Purcell Mountains southwest from Cranbrook, and the river flows south through Moyie Lake into Idaho to join the Kootenai River near Bonners Ferry, Idaho. The water quality sampling station is located at the Canada-US border at Kingsgate. This assessment is based on up to 18 years of water quality data during 1980-2004. The main human influences on water quality in the Moyie River watershed were forestry, highway transportation, and a small amount of agriculture. The water quality trends identified below have not been confirmed by statistical analysis. Conclusions: • The water was very soft and had a moderate to low (alkalinity) or moderate to high (calcium) sensitivity to acids. There was a slight increasing (improving) trend in alkalinity between 1980-95 and 2003-04, which made the water less sensitive to acids, but the calcium indicator of acid sensitivity did not change over time. • Chloride and sodium had slight increasing trends over time, possibly due to the use of highway road salt, but the levels were well below all water quality guidelines, and thus the trends were not environmentally significant. • Numerous water quality indicators had apparent declining trends from 1980-95 to 2003-04, but they were not real, being attributable to declining minimum detectable limits, artificial contamination, or lower flows and turbidity in 2003-04. • Cadmium (2003-04) and zinc (1982-2004) levels exceeded aquatic life guidelines during low flows, but this is believed to be due to the natural mineralization of the watershed, although there is evidence of past mining at Moyie Lake. • Water temperature exceeded the aquatic life guideline on two occasions in August of 1981 and 2004. • Turbidity was relatively low, probably due to the influence of Moyie Lake, but drinking water would still need partial treatment, such as filtration, plus disinfection before consumption. • Fecal contamination was low in 2003-04, and the water met the drinking water guideline for water receiving partial treatment plus disinfection. Recommendations: • The water quality of the Moyie River at Kingsgate was good with the exception of cadmium and zinc (see recommendation below), there were no apparent environmentally significant deteriorating trends during 1980-2004, and there are no proposed developments that could affect water quality. Consequently, it is recommended that routine monitoring be suspended for another 5-10 years, or until reactivation is warranted by proposed developments. • Consider investigating the sources of cadmium and zinc in the Moyie River during low flows since this is a transboundary river, and it would be prudent to confirm whether the sources are natural or human-induced. (The US water quality criteria for cadmium and zinc are an order of magnitude higher than the B.C. and Canadian guidelines and were not exceeded.) Zinc levels appeared to stay the same during 1980-2004, while cadmium measurements sensitive enough to measure the levels in the Moyie River only began in 2003-04, precluding the identification of long-term trends. • Correct the errors in the EMS database. |
