Temperature
Temperature measure of the warmth or coldness of the water is important because it affects food supply, photosynthesis, metabolism, and the solubility of gasses and minerals. For example, colder water can hold more dissolved oxygen, which is critical for fish and other aquatic organisms.
When you don’t feel well, chances are the first thing someone does is take your temperature. Water temperature is measured for several reasons. First, it determines the kinds of animals that can survive in a stream. Some organisms will die if the water temperature gets too hot or too cold. Temperature also can affect the chemistry of the water. For example, warm water holds less oxygen than cold water.