Water Quality

Objectives:

The student will be able list what tests will be done when streamkeepers look at water quality (temperature, dissolved oxygen, pH, turbidity)

The student will be able to explain what the ideal water quality test readings are for the discussed tests

The student will be able to explain the negative consequences of poor water quality in a stream

Materials Needed:

• Computers connected to the Internet
• Rivers Worksheet #S-7 (Water Quality)
• vinegar, lemon juice
• baking soda, household ammonia
• pH indicators (pH strips and/or red cabbage water)
• small jars (e.g. baby food jars)

Activities:

It is possible to go into great depth in this lesson but it is not necessary. Four things are looked at: pH, temperature, dissolved oxygen, and turbidity. Just a basic understanding of each is necessary. They should know how the mentioned factors relate to the health of the stream, and what the consequences are if the readings are not ideal in these areas.

This lesson is in two parts. The fist deals with pH and some hands on study to help student understanding. The second part deals with discussing and explaining the remaining three factors (temperature, dissolved oxygen, and turbidity) while students fill in their charts.

Printing out this lesson so you can refer to the following notes is advised To begin with, have students connect to www.kidfish.bc.ca , click on the "Our Rivers" icon, and go to the sections titled Properties of a river, Water speed, Water temperature, and Other stuff in the water sections.

Part 1

Start with pH. Examine the notes on pH below. Some hands on fun can be had here. Provide some household acids (lemon juice, vinegar) and alkalines (baking soda, household ammonia). Also provide some indicators. pH strips (litmus paper) can either be purchased through a science supply house or phone your nearby secondary school. I have always found the science teachers willing to help out. Another fun activity is to get red cabbage, shred it, barely cover it in water, boil then simmer until the water is very coloured. Put samples of this coloured water into small jars (e.g. baby food jars) then add the various acids and alkalines. There will be colour transformations!

Part 2

Hand out "Rivers Worksheet #S-7 (Water Quality)" Discuss the following topics and have students fill in the chart on the worksheet as the discussion progresses.

pH relates to how acidic or alkaline the water is. A whole unit can be done on this concept alone. For here stick to how acids are sour (lemons, vinegar) and alkaline can be bitter and slippery to touch (baking soda, household ammonia, lye). Water can be neutral (pH of 7) so there are no acid or alkaline qualities. It can become acidic (readings of 6.9 or less) or alkaline (readings of 7.1 or more). Just so they can relate to it all, litmus paper or natural indicators (e.g. red cabbage water). Examine vinegar, lemons, baking soda and household ammonia.

When water becomes acidic, at the following pH's the affects are:

• 7.0 water is neutral, everyone is happy
• 6.25 snails and tadpoles begin to die
• 5.7 trout and bass begin to die
• 4.5 caddis and mayflies start to die
• 3.5 everything is dead

(We can see why acid rain is a big issue)

When water becomes alkaline, at the following pH's the affects are:

• 7.0 water is neutral, everyone is happy
• 7.5 everyone is even happier, this is the optimum pH
• 9.5 all fish are dead

Organisms tend to more tolerant on the alkaline side. Many invertebrates prefer the alkaline since it is easier to build their shells and exoskeletons in these conditions

Temperature is very important to organisms. Certain fish like it cool. Trout like it about 15 degrees centigrade, 21 degrees stresses them out, 25 degrees is lethal. Meanwhile certain warm water fishes, like bass, have a complete different range of tolerances.

Oxygen is very important to organisms since they need this element to stay alive. The more of it that is in the water, the easier it is for the fish to breathe. Oxygen content and temperature are closely related. Warmer water holds less oxygen, colder water more. How much the stream flow is broken up also affects oxygen levels. Ideal levels are 90 to 110% saturation. This means that whatever oxygen content the water can hold, 90 to 110 % of that content needs to be there to have happy stream life. At certain places (e.g. the bottom of a cold waterfall) oxygen saturation can be very high (over 100%).

Turbidity deals with the amount of silts and sediments suspended in the water. The Fraser River looks very muddy. Its turbidity level is high. The Thompson River is a clear river with low turbidity. It is an interesting site to see the Thompson flow into the Fraser and see the two types of water mix.

High turbidity can suffocate fish. The suspended material can be abrasive to their gills or even clog them up. When there are problems with the gills, the fish can't breathe and die. When there is high turbidity, silt and sediments tend to cover the river or streambed. This covering of the gravel does not let certain species of fish (e.g. trout, salmon, and steelhead) spawn. Eggs from these fish need to be in clear gravel with an oxygen rich water flow passing over them. Of course if the silt and sediment covers them, the eggs die. Zero turbidity is ideal. Of interesting note, the Fraser River is one of the important salmon rivers in the world. It is quite turbid. Very little spawning occurs in the Fraser. The salmon migrate to clear tributaries.

Note: to demonstrate turbidity, put some fine dirt into water that is in a jar with a lid. Shake up the jar. If you take a small piece of clay and let it dissolve for a day, then shake it up, the results will be more pronounced.

Once the streamkeeper has, with the students, measured the temperature, dissolved oxygen, pH and turbidity, he/she will compare the data to a chart that is in their streamkeepers manual. From this the overall water quality can be rated. This information will be shared at the time of the stream study