Home Teachers | Mentors | Discussions | Research | Find
   Stream MonitoringCreating the Context Default   
The PathFinder Science Network

Creating
 the Context

  Home
  Research Focus
  Background Info
  Research Methods
  Data Submission
  Results of Study
  Data Analysis
  Conclusion
  Further Research


Guided
 Research

  Research Question
  Background Info
  Research Methods
  Data Submission
  Results of Study
  Data Analysis
  Conclusion
  Further Research
  Research Values


Student
 Research

  Doing Research
  Publish
  View


Tools
  Discussions
  Stream Teams
  Water Links

    Water Quality Index: Temperature
[Temperature Research Methodologies]

The water temperature of a river is very important. Many of the physical, biological, and chemical characteristics of a river are directly affected by temperature. Most aquatic organisms have adapted to survive within a certain range of water temperatures. Few organisms can tolerate extremes of heat or cold.

Temperature influences the amount of oxygen that can be dissolved in water. Cold water holds more oxygen than warm water. The more oxygen in the water, the more living things it can support. Temperature also influences the rate of photosynthesis by algae and larger aquatic plants. As water temperature rises, the rate of photosynthesis by algae and larger aquatic plants increases. The faster plants grow, the faster plants die. As plants die, they are decomposed by bacteria that consume, or use up, oxygen. Therefore, when the rate of photosynthesis is increased, the demand for oxygen in the water (BOD) is also increased.

Temperature influences the metabolic rates of aquatic organisms. Metabolic rate is the speed at which cells conduct the chemical processes of life. Most aquatic animals are cold-blooded. Their metabolic rate is slower in cold water but faster in warm. Therefore, they need more food and oxygen in warm water. They will also release more wastes.

Temperature also influences the sensitivity of organisms to toxic wastes, parasites, and diseases. Bacteria and other disease-causing organisms grow faster in warm water.

One of the most serious ways humans can harm a river is by causing thermal pollution. Thermal pollution is an increase in water temperature caused by adding warm water to a river. Industries, such as nuclear power plants, may cause thermal pollution by releasing water used to cool machinery. Thermal pollution may also result from storm water running off warm urban surfaces, such as streets, sidewalks and parking lots.

People also affect water temperature by cutting down trees. Trees help shade a river. Water exposed to direct sunlight can be as much as 20°F warmer than water that is shaded. Cutting trees often increases soil erosion. Soil erosion can contribute to warm water temperatures. Increased amounts of suspended solids carried by the river make the water cloudy or turbid. Turbid water absorbs more of the sun's rays which causes the water's temperature to rise.

© 1997-2003 PathFinder Science