Which type of stream flows for most or all of the year?

A perennial stream is characterized by its continuous flow throughout the year. This means that it typically has a consistent water source, such as groundwater discharge, that sustains its flow regardless of seasonal weather changes. Perennial streams support a diverse array of aquatic and terrestrial life due to their stable water levels, and they often contribute to larger bodies of water, like rivers and lakes.

In contrast, ephemeral streams only flow during specific periods, such as after rain events, and can dry up completely during dry seasons. Non-perennial streams may also experience variations in flow but do not maintain the year-round presence of water seen in perennial streams. Seasonal streams usually flow for part of the year, influenced by seasonal precipitation patterns, but do not maintain constant flow. Therefore, the defining feature of a perennial stream is its ability to flow throughout the entire year, making it a vital part of the ecosystem it inhabits.