Water Quality Assessment. The status and trends of water quality were assessed by reviewing the data in Excel tables, plotting the important water quality indicators over time, and comparing the values to the Province’s water quality objectives for the Cowichan River 1, or to B.C. approved 3 and working 4 water quality guidelines or Canadian water quality guidelines 5 for indicators for which objectives have not been set. Water quality indicators that were plotted include those for which water quality objectives were set, those that were monitored consistently over time, and those that exceeded water quality guidelines at times. Any levels or changes of the indicators over time that may have been harmful to sensitive water uses, such as drinking water, aquatic life, wildlife, recreation, irrigation and livestock, are described below in alphabetical order. Water quality indicators not plotted or discussed met all water quality guidelines and did not change significantly over time. These included: antimony, boron, barium, beryllium, bromide, calcium, carbon- dissolved organic, chloride, colour, fluoride, lithium, mercury, potassium, magnesium, selenium, silicon, sodium, strontium, sulphate, tellurium, tin, titanium, thallium, uranium, vanadium, and zirconium. Before the assessment was conducted, the corrections recommended by the data approval reports 6, 7 were made, and the errors, possible errors, and probable errors identified by the reports were removed from the dataset. Ammonia nitrogen – Figure 4 – had all values below average aquatic life objectives 1. There appears to have been an increasing (deteriorating) trend over time, but this impression is solely due to three higher samples in August 2001 during low flow. Cadmium (no figure) – had high minimum detectable limits (MDL), which were at or above the water quality guideline of 0.00001 mg/L at a hardness of 30 mg/L. There were four values above the water quality guideline, two of which have been identified as an error and possible error 7. An MDL at least 10 times below the guideline is needed to provide reliable data for comparison to the guideline. Chlorophyll a, periphyton – (no figure) – was measured at the station on one occasion in August 1993, and the water quality objective 1 of an average of 50 mg/m2 (0.05 g/m2) was met. In September 1998, the objective was met upstream from the Xxxxxx-North Cowichan sewage treatment plant outfall, but not met 200 m downstream from the outfall. A July 1998 survey of the river found t...
Water Quality Assessment. The status and trends of water quality were assessed by plotting the water quality indicators over time and comparing the values to the Province’s approved and working water quality guidelines (Ministry of Environment, Lands and Parks, 2001a & 2001b). Any levels or changes of the indicators over time that may have been harmful to sensitive water uses, such as drinking water, aquatic life, wildlife, recreation, irrigation and livestock, are described below in alphabetical order. Water quality indicators that were plotted but not discussed because they easily met all water quality guidelines and showed no harmful trends were: aluminum, total, arsenic, Canada – British Columbia Water Quality Monitoring Agreement 1 total, barium, total, beryllium, total, lithium, total, molybdenum, total, nickel, total, selenium, total, sodium, strontium, total, and vanadium, total. 0.005 mg/L irrigation guideline for trivalent chromium, and three of these values exceeded the 0.008 mg/L irrigation guideline for hexavalent chromium. The three highest values were measured when turbidity was low (0.83-2.6 NTU), and thus the chromium was not associated with suspended sediment and may have been in a bio-available form. Measurement of hexavalent and trivalent chromium with suitably low detection limits (at least 0.0001 mg/L) are needed to determine the extent to which guidelines are exceeded. There was no apparent change in mean total chromium levels during 1991-2000. Canada – British Columbia Water Quality Monitoring Agreement 2 Coliforms, fecal (Figure 12) were monitored during 1968-70 and 1975-2000. There was a dramatic decrease in fecal coliform levels after 1977 and then little or no change during 1978-2000. The decrease after 1977 was probably due to improved sewage treatment and disposal by the Town of Creston and in the US. The maximum level during 1978-2000 was 210/100 mL, and the next highest value was 99/100 mL, indicating that the water met the guidelines for swimming, livestock and irrigation (200/100 mL geometric mean) and raw drinking water that receives partial treatment and disinfection (100/100 mL 90th percentile). Canada – British Columbia Water Quality Monitoring Agreement 3 During 1974-2000, there has been a small increasing trend, but it had little environmental significance since the maximum hardness (hardness is mainly calcium plus magnesium expressed as CaCO3) of 139 mg/L was well below the poor, but tolerable, aesthetic guideline for drinking water.
Water Quality Assessment. The status and trends of water quality were assessed by plotting the water quality indicators over time and comparing the values to the Province’s approved and working water quality guidelines (Ministry of Environment, Lands and Parks, 2001a & 2001b). Any levels or changes of the indicators over time that may have been harmful to sensitive water uses, such as drinking water, aquatic life, wildlife, recreation, irrigation and livestock, are described below in alphabetical order. Water quality indicators that were plotted but not discussed because they easily met all water quality guidelines and showed no harmful trends were: aluminum, total, barium, total and extractable, beryllium, total and extractable, boron, extractable, gallium, extractable, lanthanum, extractable, lithium, total and extractable, molybdenum, total, nickel, total and extractable, nitrogen, total dissolved, selenium, total and extractable, strontium, total and extractable, thallium, extractable, uranium, extractable, and vanadium, total and extractable. Trace elements at this station were measured by total and extractable methods. Total and extractable samples are both acidified in the field with nitric acid to about pH 2. Extractable zinc samples are then analysed in the laboratory without further treatment, while total zinc samples have additional nitric and hydrochloric acid added and are boiled to dryness before analysis. The additional extraction step has the potential to extract trace elements that are strongly bound to particulate matter and unlikely to be bio-available. The aquatic life guideline was always met during 1984-2000. Only data with a detection limit of 0.0001 mg/L, which is still above the aquatic life guidelines (0.00003-0.00006 mg/L), were included. Nevertheless, there were many detectable values above the guideline during 1973-2000, mostly occurring in freshet due to elevated turbidity, suggesting that the cadmium was particulate-bound and not likely to have been bio-available. Some of the detectable values may also be false positives since the values were all close to the detection limit. The maximum value of 0.0018 mg/L was still below the drinking water guideline of 0.005 mg/L. There may have been a slight decrease over time. These peaks occurred during spring freshet due to elevated turbidity and thus were probably not bioavailable. There were no apparent changes over time. Cobalt, extractable (Figure 14) was monitored during 1997-2000 with a detection limit of...
Water Quality Assessment. The status and trends of water quality were assessed by plotting water quality measurements for the Flathead River at the International Boundary on a graph over time, along with the relevant approved 2 and working 3 water quality guidelines or the Canadian water quality guidelines 4. (There are no site-specific water quality objectives for the Flathead River.) The data are plotted in Figures 3 to 31. (Note: For this assessment, 1980-95 data came from EMS 0200047 and 2002-04 data came from ENVIRODAT BC08NP0003). The graphs were inspected for "environmentally significant" trends - where the measurements are increasing or decreasing over time and the levels are close to the objectives or guidelines, or are otherwise judged to represent an important change in water quality. These trends are further evaluated to ensure that they were not caused by measurement errors, to identify their causes, and to determine whether they are statistically significant. A confidence level of 95% or better is used to define statistical significance, unless noted otherwise. When concentrations of a substance cannot be detected, we have plotted the concentration at the level of detection. We believe this to be a conservative approach to assessing possible trends. As well, there are times when measurements were not taken for some reason. In these cases, straight lines will join the two consecutive points and may give the illusion on the graph of a trend that does not exist. In some cases, testing for the presence of a variable has been terminated after a certain period. In general, this has been because a previous data assessment and review has indicated that collections of these data are not warranted for this station. For other variables, concerns about concentrations may have only arisen in recent years. Any levels or changes of the indicators over time that may have been harmful to sensitive water uses, such as drinking water, aquatic life, wildlife, recreation, irrigation and livestock, are described below in alphabetical order. Water quality indicators that were reviewed but not discussed because they easily met all water quality guidelines and showed no harmful trends were: antimony, barium, bismuth, boron, bromide, dissolved organic carbon, chloride, fecal coliforms, true colour, specific conductivity, gallium, lanthanum, lithium, molybdenum, potassium, rubidium, selenium, silver, sodium, strontium, sulphate, air temperature, thallium, uranium, and vanadium. The data for 198...
