A tributary is a stream or river that flows into a larger water body, such as another river or a lake. These waterways collect water from the surrounding landscape, directing it into larger channels.
Defining a Tributary
A tributary is precisely defined as a stream or river that converges with and flows into a larger stream, river, or a lake. A key characteristic is that a tributary does not flow directly into a sea or ocean. The larger watercourse that a tributary joins is commonly referred to as the “main stem” or “parent” river. The main stem represents the primary downstream segment of a river system, distinct from its contributing branches. Tributaries contribute water, sediments, and dissolved substances to the main river, increasing its overall flow and content.
Different Types of Tributaries
Tributaries can be categorized based on their flow patterns. Perennial tributaries maintain continuous flow throughout the year. Their consistent water supply is typically sustained by groundwater, providing a steady base flow, or by persistent rainfall and melting snowpacks.
Intermittent tributaries experience flow only during specific periods of the year. They often flow during wetter seasons or after significant precipitation, becoming dry during prolonged spells. Their water source can fluctuate between surface runoff and groundwater contributions.
Ephemeral tributaries flow exclusively during and immediately following precipitation events. They are typically dry for most of the year, activating only in direct response to rainfall or snowmelt. These are often the smallest and highest-elevation streams within a river network.
Tributaries and the Greater River System
Tributaries are integral to river networks and hydrological systems like watersheds or drainage basins. They gather water from catchment areas, channeling it towards the main river, which significantly augments its volume and flow.
These interconnected water systems are also important for various biological processes. They offer diverse habitats for aquatic organisms and the plant and animal life along their banks. Tributaries are also active in transporting nutrients, sediments, and organic matter throughout the entire river system.
It is helpful to understand how a tributary differs from a distributary. A distributary is a stream or river that branches off and flows away from the main river. Distributaries are commonly observed in river deltas, where a main river divides into multiple smaller channels before discharging into a larger body of water like an ocean. Unlike tributaries that add water to a main river, distributaries reduce its volume by diverting flow.