Temperature Collection Protocols
Background Temperature is very
important to aquatic life. Most aquatic organisms are cold blooded, so their body temperatures are the same as
the water temperature. Table 1 describes the kinds of stream life at various temperatures. Water temperature
increases when the sun shines directly on a stream. Shading from trees, water surface area and volume, turbidity,
stream bed colour, and orientation to the sun all affect the amount of sunlight absorbed by water.
TABLE 1: Optimal Stream Life At Various Temperatures
TEMPERATURE RANGE TYPES OF STREAM LIFE 20-25°C (warm) lots of plant life; high fish disease risk; warm water fish (bass, carp, crappie, catfish, bluegill); caddisflies, dragonflies 13-20°C (cool) plant life; moderate fish disease risk; trout, salmon, sculpins; stoneflies, mayflies, caddisflies, water beetles,water striders 5-13°C (cold) plant life; low fish disease risk;trout, salmon, sculpins; stoneflies, mayflies, caddisflies Oxygen Warm water contains less oxygen than cold water. When the water temperature increases, the concentration of dissolved oxygen decreases. As the temperature rises, animals use oxygen at a faster rate - the metabolic rate doubles with each 10°C increase. Plants grow faster and produce more oxygen. However, their decomposition consumes more oxygen. As the water temperature increases, animals become stressed and are more likely to succumb to contaminants, parasites, and disease. Organisms die when they cannot adapt to the new conditions.
Shade Shading helps keep summer water temperatures low. Shaded streams are cooler than unshaded streams. In late summer, the water temperature increases between early morning and late afternoon. In unshaded streams, the daily increase can be as great as 10°C. Water loses heat very slowly even when it flows into shaded areas.
Streamside Vegetation Removal of streamside vegetation is a major cause of temperature problems in British Columbia streams. Logging, agriculture, dyking, and urban development often remove streamside vegetation. This adds sediment to the stream from erosion. Besides causing other water quality problems, sediment absorbs heat from the sunlight thereby raising water temperature. Planting streamside vegetation helps correct the problem.
Water Removal Water withdrawal for irrigation purposes often reduces stream flow during the summer, when flows are already at minimum levels. Low water flows contribute to problems with daily temperature fluctuation because there is less water to buffer the impact of high temperatures. Thermal pollution from industrial sources also causes increased water temperatures. In addition discharges of water used as coolant may contain toxic antifouling agents or chlorine from municipal water sources.
Procedures for Measuring Water TemperatureRecords Record Stream Name and Date and Time of the Measurement. In order that you can repeat temperature measurements at the same location on different dates, be sure to record the location of your measurement site on a map of the stream or with reference to a particular landmark along the stream: ie. .5 km below a bridge, etc.
Thermometer Keep thermometer in water 2 minutes and hold the bulb of the thermometer approximately 10 cm below the water surface. Take the reading while the thermometer is still in the water. If you are concerned about daily temperature changes, make two readings, one in the morning and one in the afternoon. For each, record the time of day, air temperature, and water temperature. (Note: it is customary to take the air temperature before taking the water temperature.)
Readings
Time of am reading: __________ ...of pm reading: __________
Morning Temperature:
Air (°C) ______ Water (°C) ______ Afternoon Temperature: Air ______ Water ______ Differences: am-pm: Air ______ Water ______ Differences If you are concerned about the differences between the water temperature in different sections of the creek, as in a section of the creek which is shaded by trees compared with a section which is open and unshaded, then take measurements at the different sites, and record the different locations in detail.
Site 1 Air (°C) ______ Water (°C) ______ Site 2 Air ______ Water ______ Site 3 Air ______ Water ______ Now you can LogIn and enter your data, or learn about other Water Studies Data Collection Protocols.