An ephemeral stream is a stream or part of a stream that flows as a result of precipitation and is above the ground water reservoir. Ephemeral streams are found at southwestern perennial stream headwaters.
Fifty-nine percent of all U.S. streams are classified as ephemeral, and 81 percent of the streams in the Southwest are considered ephemeral. Ephemeral streams are useful fin the transport of sediment, chemicals, nutrients and other natural materials. They also function as connections between bodies of water within a watershed. These streams interact in a similar manner as perennial streams, providing nutrients and functions to a system, but at different times.