Water Quality Monitoring: Temperature Change

Temperature Change

Temperature affects many physical, biological, and chemical characteristics of a creek: amount of oxygen that can be dissolved in water, rate of photosynthesis of plants, metabolic rates of animals, and the sensitivity of organisms to toxic wastes, parasites, and diseases.

Thermal pollution is an increase in water temperature caused by adding relatively warm water to cooler stream water. The warm water can be stormwater running off warmed urban surfaces, such as streets and parking lots, which are often constructed of black, heat-absorbing asphalt.

The cutting down of trees that shade a river will expose it to sunlight and increase temperature. Turbidity in water increases the amount of heat absorbed from sunlight.

Measurement of temperature change can help detect sources of thermal pollution and suggest the size of habitat for organisms that are more sensitive to temperature variation.

Test Equipment

LaMotte thermometer (Code 1066) with string attached

Procedure

At the test site where the other water quality tests are being performed and close to the time that the dissolved oxygen sample is being taken, lower the thermometer approximately ten centimeters below the water surface.
Keep the thermometer in the water until a constant reading is attained. Other meters remain for three minutes and this is recommended for the thermometer as well.
Remove the thermometer from the water and read the temperature as quickly and as accurately as possible. Read to the nearest 0.1 degree. Do not shake the thermometer, since it will cause the reading to change more quickly. Record the water temperature on the field data sheet.
Proceed to the upstream location where Adams meets the creek. The sidewalk on the north side of the creek will lead you there. Use the string to dangle the thermometer over the fence and into the water for three minutes, read, and record the upstream temperature as before. Try to find a place within reach where the physical conditions most resemble those at the test site.
Proceed to the downstream location where Pierce crosses over the creek. The path on the south side of the creek will lead you there. Use the string to dangle the thermometer over the side of the bridge and into the water for three minutes, read, and record the downstream temperature as before. Try to find a place within reach where the physical conditions most resemble those at the test site.

Water Quality Index

Calculations

Subtract the upstream temperature from the temperature downstream and record the result as temperature change (C).

Convert temperature change (C) to water quality index.

 Temperature change:  (C)

                     

Water quality index: