Water Stewardship Information Sources
| Citation | Lucas, B. 1998. Water quality inventory of the Nitnat River and San Juan River watersheds, Vancouver Island, British Columbia, 1997. Prepared for BC Ministry of Environment. |
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| Organization | Ministry of Environment |
| URL | http://www.env.gov.bc.ca/wat/wq/studies/nitinat.pdf |
| Abstract/Description or Keywords | To provide information on water resources in six major watersheds on the west coast of Vancouver Island, a water quality inventory was conducted between May and November, 1997. The project was designed to provide information on any limitations to drinking water or other potential water uses (e.g. recreation, fish habitat). The quantity aspects of water resources are being addressed in a separate report. Sixty-one sites were identified and each sampled four times through the period, representing spring, summer, and fall. At each station, samples were collected for a wide variety of characteristics: Giardia, Cryptosporidium, fecal coliforms, and a wide range of water chemistry parameters. In terms of suitability for drinking water, the majority of sites had limitations of some kind. An important result was the relatively high fecal coliform bacteria levels in many of the streams in this relatively uninhabited and undeveloped area. The periodic high bacteria levels would indicate the need for treatment beyond the normal disinfection typically used for drinking water supplies. High fecal coliforms appear to be somewhat associated with relatively high turbidity or non-filterable residue concentrations. Lake sites had some advantages over stream sites as potential drinking water sources because of low nonfilterable residues and fecal coliforms compared to streams. Concentrations of Giardia and Cryptosporidium were low but there were occurrences found throughout the study area at different times. Again this was an unexpected result in this area with a low human population and where the major activity is forestry harvesting. It appears that the most frequent presence was in the watershed with the highest human population (Nitinat) but these two protozoans can, on the results of this study, be expected to occur in all streams in the study area, even those which would otherwise be considered to be undisturbed or unaffected by human activity or presence. The water chemistry characteristics that exceeded criteria for drinking water at some sites included color, iron, organic carbon, and some metals. These are important in some cases and of secondary consideration in other cases. There was a fairly wide variation in the levels of a number of characteristics that were measured - due primarily to fluctuations in stream flow. There was considerable variation from the weather normals during this year. In general the summer was quite wet (stream flows were relatively high) and there was no marked autumn freshet brought on by fall storms as is usually the case. This report provides a regional characterization of water quality that should provide a baseline for future sampling and a reference by which to judge any changes that might occur. The major constraints to use as drinking water are the protozoan pathogens, microbial pathogens that are indicated by the presence of fecal coliforms, suspended sediments (which affect disinfection efficiency and general appearance of the water), and dissolved organic carbon (which reacts with chlorine disinfectant to form trihalomethanes which are known carcinogens). There do not appear to be any major constraints to recreation due to water quality and no obvious effects on aquatic life that are due to the water quality parameters that were measured. |
| Information Type | report |
| Regional Watershed | Vancouver Island South |
| Sub-watershed if known | Nitinat River, San Juan River |
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| Project status | complete |
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