Stream Types
Streams and rivers are primarily characterized by flow. There are three main types of streams: perennial, intermittent, and ephemeral. Perennial streams and rivers are those that flow year-round. Some perennial streams and rivers in Texas are fed by large springs (Comal River, San Felipe Creek, San Marcos River, or Devils River). Due to the intermittent nature of most streams in Texas, the headwaters of many streams are effluent discharges from wastewater treatment plants. These discharges create artificial perennial streams. Many urban streams are considered effluent dominated.
Intermittent streams and rivers are those that become dry for a period of a week or longer each year. Over 76 percent of the streams in Texas fall into the intermittent category. These water bodies are generally associated with arid or semi-arid areas or areas of average rainfall that are experiencing especially dry conditions, but intermittent streams can be found throughout Texas. During times of extreme drought, even perennial streams can become intermittent. Although shallow sections of intermittent streams and rivers can dry up, perennial pools are often maintained in the deeper sections of a stream channel. Large pools can often sustain aquatic life through the hot summer months.