Stream watch

Measuring the health of our streams

By Kristina Swerhun,

Whistler Naturalists

Now that summer is on it’s way, people are out and about enjoying the weather, construction is in full force, and lawns and gardens are getting tended to. What is all this activity doing to our streams? Nobody knows for sure, but we’re getting closer with help from dedicated volunteers, maybe even you.

In 2000 the Whistler Fisheries Stewardship group started a volunteer water quality monitoring program. For the first time, Whistler had consistent information on the state of our streams, with the added advantage of not being driven by development pressure. Each summer data is collected and used to figure out what changes are going on and then hopefully find out why. Monitoring also helps evaluate the success of any rehabilitation projects. Here is what’s being tested for and why, courtesy of the Streamkeepers Handbook from the Department of Fisheries and Oceans.

Temperature: Most aquatic organisms are cold blooded, so their body temperatures are the same as the water temperature. Shading from trees, water surface area and volume, turbidity, stream bed colour, and orientation to the sun all affect stream temperature. When the water temperature goes up, the concentration of dissolved oxygen goes down. As the temperature rises, animals use oxygen at a faster rate, become stressed and are more likely to succumb to contaminants, parasites, and disease. In warmer water plants will also grow faster and therefore produce more oxygen – however, when plants die, their decomposition consumes more oxygen. Lakeside Creek had the highest average temperature last summer at 16.5 ° C while Fitzsimmons Creek was lowest at 9.7 ° C.

Dissolved Oxygen: The amount of oxygen dissolved in water affects the number and kind of animals found there. Healthy streams are saturated with oxygen (90 to 110 per cent) during most of the year. Oxygen can get mixed into water by turbulence or added by plants as explained in the previous paragraph. Oxygen is removed from the water by organic wastes, such as sewage and fertilizer, as they decompose and also by plant and animal respiration. Planting stream bank vegetation helps to increase oxygen levels in streams. Foliage provides shade and roots absorb nutrients. Controlling sources of sewage, animal waste and fertilizer also helps. 19 Mile Creek had the highest average oxygen concentration last summer while Lakeside Creek had the lowest.

pH: The pH scale measures the relative acidity or alkalinity of any substance. The scale ranges from very strong acid, at pH 0 (e.g. battery acid has a pH of 1), to a very strong base, at pH 14 (e.g. bleach has a pH of 12). Pure water (H 2 0) has a neutral pH of 7, which means it has an equal concentration of H + (hydrogen) and OH- (hydroxyl) ions. Acidic water has a high concentration of hydrogen ions and a low concentration of hydroxyl ions. The scale is logarithmic, so a one unit difference in pH reflects a tenfold change in acid or alkaline concentration. Most aquatic organisms are sensitive to small pH changes and prefer a pH of 6.0 to 8.5. Stream pH level depends on the geology of the surrounding area, and usually falls within this range. All streams monitored last year were between pH 6.5 and 7.5.

Turbidity: Turbidity is a measurement of the cloudiness caused by sediment, microscopic organisms, and pollutants. These suspended particles restrict light penetration in the water, which in turn affects algal growth and oxygen production. Sediments can clog gills or other breathing structures of fish and benthic invertebrates. When sediment settles to the stream bottom, it can smother fish eggs and ruins habitat used by fish and aquatic insects. Most streams measured last summer had good or medium turbidity, with the exception of Fitzsimmons Creek that ranged from medium to poor.

If you’re interested in getting to know your local stream a little better, or would like more information, please contact Kristina at 604-935-8323 or

Upcoming Events:

Monthly Bird Walk — The next bird walk will take place Saturday, July 3rd. Join Whistler experts in the monthly update of our feathered locals and migrants. For details, contact Michael Thompson at 604-932-5010.

Calling all Aspiring Nature Writers and Photographers — Have an interest in natural history? Want to educate others about your favourite flora and/or fauna? Write your very own Naturespeak article or send us your photos to accompany our articles. For more information contact Sorcha Masterson at 604-932-5089 or


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