At lower temperatures, more oxygen can be dissolved in the water because the gas molecules are moving slower and are more compact. At higher temperatures, dissolved oxygen and other gases in water move faster and spread farther apart, including out of the water. Also at higher temperatures, the water molecules may move faster and bump out oxygen. As water temperature rises, it increases the metabolic rates of fish and aquatic insects. Temperature also influences another natural stream process.
Decomposition uses oxygen and produces carbon dioxide instead.
At higher temperatures, evaporation rates increase and the water vapor leaves behind the total dissolved solids. Concentrations of the dissolved solids will increase, as the body of water becomes shallower. High total dissolved solid concentrations can harm aquatic life. Refer to the Total Dissolved Solids Information Sheet for more information. There is a natural fluctuation of waterway temperature from season to season, even day and night, and aquatic life can cope with these natural changes.