Water Temperature
Water temperature is important because it affects the rates of biological processes and chemical processes. Temperature is measured in degrees Fahrenheit (180° between the freezing and boiling point of water) or degrees Celsius (100° between the freezing and boiling point of water).

The optimal health of aquatic organisms from microbes to fish depends on temperature. If temperatures are outside the optimal range for a prolonged period, organisms are stressed and can die. For fish, the reproductive stage (including spawning and embryo development) is the most temperature-sensitive period. Macroinvertibrates (for example, insects, crayfish, worms, clams, and snails) will move about in the stream bed to find their optimal temperature.

The temperature of the water also affects the volume of dissolved oxygen (DO) it can hold (water's ability to contain dissolved oxygen decreases as water temperature rises), the rate of photosynthesis by aquatic plants, metabolic rates of aquatic organisms, and the sensitivity of organisms to pollution.

Water temperature is affected by the seasons and can also be affected by weather, removal of shading stream bank vegetation, building dams on rivers, discharging cooling water, discharging storm water, and groundwater influx.

Water Temperature in the Red River
As shown on the graph, the water temperature in the Red River varies seasonally from just above freezing (0°C or 32°F) in the winter to over 25°C (over 77°F) in the summer. Among other things, this seasonal change in river water temperature causes seasonal changes in the level of dissolved oxygen and in the level of ammonia gas in the river.

Graph of water temperature (°C) for the Red River in the FM metro area for the period
July 1990 to July 2001.

Click Here to test your knowledge of Red River water quality.