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State of the Water Quality

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The state of the water quality was judged by comparing values to the Ministry of Environment, Lands and Parks' Approved and Working Criteria for Water Quality (Nagpal et al., 1995). With only three years of samples, the record is too short and sparse to comment on any trends. The following 24 water quality indicators were not discussed as they easily met all water quality criteria and showed no clearly visible trends: alkalinity, arsenic, barium, beryllium, calcium, carbon (total inorganic), chloride, cobalt, cyanide (total and weak-acid dissociable), conductivity, fluoride, lithium, magnesium, molybdenum, nickel, nitrate/nitrite, total dissolved nitrogen, potassium, filterable residue, fixed filterable residue, fixed non-filterable residue, selenium, silica, sodium, strontium, sulphate and vanadium.

Flow (Figure 2) values were highest during snowmelt freshet (April-July) and fall rains (September-October).

Total alkalinity (Figure 3) and calcium (Figure 9) concentrations indicated a low sensitivity to acid inputs.

Total aluminum (Figure 4) values exceeded the 5 mg/L total aluminum criterion for wildlife, livestock and irrigation only once (July 4, 1991) during freshet when non-filterable residue was high. This suggests that aluminum was in a particulate form and was probably not biologically available. Dissolved aluminum should also be measured to permit comparisons to criteria for drinking water and aquatic life.

Total cadmium (Figure 8) had a minimum detectable limit (0.0001 mg/L) 3 to 10 times above the aquatic life criteria (0.00001 mg/L, 0.00003 mg/L). Most high cadmium values corresponded to periods of high non-filterable residue. This suggests that cadmium was in a particulate form and probably not biologically available. To evaluate the aquatic life criteria accurately, the minimum detectable limit should be lowered to at least one-tenth of the lowest criterion, and dissolved cadmium should also be measured.

Total organic carbon (Figure 11) values exceeded the 4 mg/L criterion for drinking water once (May 6, 1992). Dissolved organic carbon should be measured due to its role in influencing the toxicity of metals.

Total chromium (Figure 13) exceeded the 0.002 mg/L criterion for phyto- and zoo-plankton 44% of the time. No values exceeded the 0.02 mg/L criterion for fish or the 0.05 mg/L criterion for drinking water. High chromium and non-filterable residue occurred together. This suggests that chromium was in a particulate form and probably not biologically available. Dissolved chromium should also be measured in the future.

Apparent colour (Figure 15) values were highest in the summer and near the minimum detectable limit (5 units) in the winter. The 15-unit drinking water and recreation criterion for true colour was met at least 62% of the time. No values exceeded the 100-unit recreation (maximum) criterion. All criteria are given as true colour values, where turbidity is removed before measurement. High apparent colour values occurred in samples with high turbidity, and thus true colour would have been much lower. True colour should be measured at the site to compare the data to the criteria effectively.

Total copper (Figure 16) exceeded both the upper (0.004 mg/L) and lower (0.002 mg/L) aquatic life criteria in all samples. High copper and non-filterable residue occurred together. This suggests that copper was in a particulate form and probably not biologically available. However, copper exceeded the criteria even when non-filterable residue and turbidity were low, indicating that the Unuk River had naturally high copper levels. Dissolved copper should also be measured in the future.

Hardness (Figure 20) samples were within the optimum range for drinking water (80-100 mg/L as CaCO3) 19% of the time. Eighty-one percent of the values were below this range, but still quite acceptable (soft) for drinking water. Lowest hardness values took place in the summer and highest values occurred in the winter, reflecting the increased proportion of harder ground water during winter low flows.

Total iron (Figure 21) exceeded the 5 mg/L criterion for irrigation 19% of the time, while the 0.3 mg/L drinking water and aquatic life criteria were exceeded 81% of the time. High values of iron and non-filterable residue occurred together. This suggests that iron was in a particulate form and probably not biologically available. Also, the particulate iron would be removed during drinking water treatment needed to remove the turbidity caused by the particulate matter. Dissolved iron should be measured in the future.

Total lead (Figure 22) values exceeded the 0.006 mg/L upper criterion for aquatic life twice (July 4, 1991 and May 18, 1993) and exceeded the 0.004 mg/L lower criterion four times. High lead and non-filterable residue occurred together. This suggests that lead was in a particulate form and probably not biologically available. Total and dissolved lead should be measured in the future.

Total manganese (Figure 25) exceeded the 0.2 mg/L criterion for irrigation once (July 4, 1991). Also, the 0.1 mg/L criterion for aquatic life was exceeded 19% of the time and the 0.05 mg/L criterion for drinking water was exceeded 44% of the time. High manganese and non-filterable residue occurred together. This suggests that manganese was in a particulate form and probably not biologically available. Also, manganese would be removed by the water treatment needed to remove turbidity prior to drinking. Dissolved manganese should also be measured in the future.

pH (Figure 30) exhibited a slight downward trend, although the data are sparse and the record is short. All criteria were met.

Non-filterable residue (Figure 34) values exceeded the 25 mg/L criterion for good fisheries 44% of the time, although this criterion may not be applicable to all mountain and northern streams. Total phosphorus (Figure 31) reported higher values corresponding to high non-filterable residues. This suggests that total phosphorus was in a particulate form and not biologically available. Higher non-filterable residues were associated with higher flows.

Water temperature (Figure 44) did not exceed the 15°C upper aesthetic limit for drinking water and the lower limit for recreation. This means that the water was cool enough to be aesthetically pleasing for drinking, but too cold for water-contact recreation such as swimming.

Turbidity (Figure 45) values exceeded the 50 NTU criterion for recreation twice (July 4, 1991 and May 18, 1993). The 5 NTU aesthetics criterion for drinking water was exceeded 56% of the time, and the 1 NTU health criterion for drinking water was exceeded 88% of the time. Higher turbidity values were associated with higher flows. Turbidity removal and disinfection are required prior to drinking water use.

Total zinc (Figure 47) exceeded the 0.03 mg/L fish and invertebrates criterion twice (July 4, 1991 and May 18, 1993). Also, 38% of the values exceeded the 0.015 mg/L algae criterion. High zinc and non-filterable residue occurred together. This suggests that zinc was in a particulate form and probably not biologically available.

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