Tributaries

A tributary is a stream or river that flows into another river or lake. It contributes water, sediment, and nutrients to the receiving watercourse and is part of a larger drainage basin or watershed.

In a river system, tributaries are joined by others along the main stem; they are named as left or right tributaries depending on their side relative to the flow direction of the main river. The point where a tributary meets the main river is called a confluence. Tributaries can be perennial, carrying water year-round, or intermittent and seasonal, or ephemeral in dry seasons.

Classification: Small streams may be called first-order; when two streams of same order meet, order increases. Larger tributaries can have their own tributaries, creating a hierarchical network.

Examples and significance: Major river systems rely on extensive networks of tributaries to drain their basins. They influence flood dynamics, sediment transport, and ecosystem diversity. Notable examples include the Mississippi River system with tributaries such as the Missouri and Ohio; the Danube with Inn and Drava; the Amazon with numerous tributaries.