What is Temperature?

Temperature is the measurement of the heat energy of the water, and, for many scientific applications, Temperature is measured in degrees Celsius. Temperature is affected by many factors, including ambient air temperature, flow and volume of water in the waterway, stormwater runoff, as well as other natural and human sources of physical and chemical thermal pollution.

Why is Temperature important?

Aquatic plants and animals are evolutionarily adapted to live in different ranges of Temperature with gradual changes due to changing seasons. When the Temperature of the water changes rapidly and exceeds the acceptable range for various aquatic organisms, those organisms may die, become stressed, or become excluded from their habitat. Other critical water-quality parameters, such as Dissolved Oxygen, are dependent on Temperature.

How do we measure Temperature?

Temperature is measured with a probe that is lowered by staff or volunteers into the water at each station location. Temperature readings are recorded half-way between the water’s surface and the river bottom. We assess the Temperature data using the State of Maryland’s instantaneous numeric thresholds of 32°C (Use Class I streams and rivers), 23.9°C (Use Class IV), and 20°C (Use Class III), which ensures the protection of the ecological health of fish populations in the State’s streams and rivers.