What We Test

We conduct monthly and quarterly stream testing and annual BIBI testing. (For information on BIBI testing, see below.)

Our regular stream testing consists in large part of collecting small samples of stream water, adding various testing chemicals, and observing the results—for example, adding drops until a purple liquid turns clear. We also take samples for biological testing, measure stream and air temperature, and obtain other data. We work in small teams using a kit that contains all chemicals and equipment and complete instructions. There is always a certified stream tester on each team.

When we do monthly testing, a single team visits one site on McAleer Creek and one site on Lyon Creek.

When we do quarterly testing, we test two sites on each stream. One team visits a site on McAleer Creek where the water enters the City and another site on McAleer Creek near Lake Washington. The other team does the same on Lyon Creek. This tells us what pollutants each stream picks up in Lake Forest Park.

These are the variables we test:

Temperature: Salmon and many other fish require cold or, at least, cool water. This is why shady stream banks are beneficial.

The preferred temperatures vary by species, season of the year, and other factors. Temperatures greater than 21⁰ Celsius in the warmer months have been shown to affect migratory patterns of salmon. One important reason why cold water is important is that stream temperature has a direct correlation with the dissolved oxygen (DO) and oxygen saturation.

Dissolved Oxygen (DO): Aquatic plants and animals need oxygen.

The Washington State Department of Ecology DO threshold for a healthy stream is 8.0 parts per million. Moving water and cool water hold more dissolved oxygen than still water and warm water. Dissolved oxygen is also reduced by bacteria. From DO and stream temperature, we calculate the oxygen saturation of our streams. Oxygen saturation is the amount of oxygen in the stream as a percentage of the maximum amount that is possible given the current stream temperature (and atmospheric pressure). 

Alkalinity: Alkalinity protects water against changes in pH, making it more stable for aquatic life.

Alkalinity is a measure of buffering capacity of water. Alkalinity “protects” pH status with two-way reactions with acids and bases, helping to minimize their impact on pH. If acid goes up the reaction goes basic and vice versa.

Hardness: Hardness is a measure of the amount of dissolved calcium and other minerals.

The primary dissolved mineral in stream water is calcium carbonate. Water may be hard for natural reasons such as limestone stream beds but may also be hard due to human activity. Therefore hardness can be used to measure the influence of human activity in the watershed. Much like human beings, fish need calcium and other minerals. Hardness below 15 mg/L or above 200 mg/L may be harmful to fish and other aquatic organisms.

pH: pH is a measure of the level of acidity or alkalinity.

A pH of 7.0 is neutral. Water with a pH below 7 is acidic, above 7 is basic. A pH of 7 to 8 is best for fish. 

Turbidity: Turbid water is cloudy. Of course, clear water is better.

Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, like smoke in air. High turbidity can prevent light getting to lower depths, inhibiting the growth of plants and the fish and invertebrates that depend on them. In addition, high turbidity can inhibit gills’ ability to absorb DO.

Coliform Bacteria: These bacteria come mainly from the intestines of mammals and birds. E. coli is a potentially dangerous type of fecal coliform bacteria.

Fecal coliform bacteria in local streams results from the excrement of humans, livestock, wildlife, and dogs and cats. Because E. coli bacteria are live organisms, specific conditions, such as winter rain run-off, can quickly increase the E. coli count. Negative conditions such as cool water, aeration, and even direct sunlight can decrease E. coli.

BIBI Testing

Once a year, we conduct BIBI testing on both McAleer Creek and Lyon Creek. We scoop up samples of sediment from the stream bottom and, using tweezers, carefully pick out insects and other invertebrates. Then a professional entomologist provides a scientific rating of the health of our two streams. BIBI testing is a well-established procedure in environmental science, developed by Dr. James Karr, of the University of Washington.

Again, no experience is necessary to participate, a certified stream tester is part of each team. The work is surprisingly enjoyable. We begin shortly after our 9:00 am meeting on the lower level of Town Center and finish up at about 12:30. You get close to nature and become “intimately” familiar with our streams.

For the curious, "BIBI" is short for Benthic Index of Biotic Integrity. "Benthic" refers to the stream bottom.

Updated 12/13/2019