What is it called when a stream flows into a river?

When a stream flows into a river, it is called a tributary. A tributary is a smaller stream or river that flows into a larger stream or other body of water. The larger river or body of water into which the tributary flows is called the main stem or main channel.

Tributaries can play a significant role in the hydrology of a river system, as they can contribute a significant portion of the water and sediment that flows through the main stem.

Tributaries can also contribute to the formation and evolution of the landscape, as they can erode and deposit sediment as they flow.

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The Importance of Tributaries in Maintaining Ecosystem Balance


Tributaries support a wide range of plants and animals, including fish, birds, amphibians, and mammals. Many species rely on these tiny rivers and streams for refuge, food, and breeding grounds, and their presence is crucial to the health and variety of local ecosystems.

Water quality

They serve an important role in keeping bigger rivers and lakes clean. They aid in the filtering of sediments and contaminants, as well as the provision of oxygen and nutrients to aquatic life.

Flood control

They can assist and reduce flood damage by offering multiple paths for surplus water to move. This aids in the prevention of erosion, property destruction, and other negative consequences of floods.

Hydrological cycle

Tributaries play an important role in the hydrological cycle, which involves the transportation of water from the Earth’s surface to the atmosphere and back again. They contribute to the general health and balance of the water cycle by replenishing groundwater and surface water and assisting in the regulation of river flow.

The Impact of Human Activity on Tributaries


Human activities may have a considerable influence on them. These effects can be both bad and beneficial, depending on the activities and how they are carried out.

Human activities affect tributaries in the following ways:


Pollutants released into tributaries by human activities like as industrial and agricultural operations can harm aquatic life and impact the general health of the river.


Buildings, roads, and other infrastructure near streams can disturb the natural flow of the water and disrupt the habitats of plants and animals that rely on the tributary for existence.

Dams and diversions

Dams and diversions can be built on tributaries to generate hydroelectric power or to control the flow of water for irrigation or other purposes. These constructions can affect the normal flow and ecology of the tributary and may potentially damage the downstream environment.

Land use changes

Land use changes, such as the conversion of forests or grasslands to agricultural areas, can have an impact on the water quality and quantity of rivers.

Classifying Tributaries

Some common ways to classify tributaries include:

By size

Tributaries are always categorized according to their size, with bigger tributaries known as “major tributaries” and lesser tributaries known as “minor tributaries.”

By location

Tributaries can also be classed according to their proximity to the main river or stream. For example, tributaries that enter the main river from the same side are referred to as “right-bank tributaries,” but tributaries that enter from the opposite side are referred to as “left-bank tributaries.”

By flow direction

They can also be classed depending on their flow direction, with those that enter the main river from upstream referred to as “headwater tributaries” and those that enter from downstream referred to as “tailwater tributaries.”

By water source

Tributaries can also be classed according to their source of water, for example, whether they are fed by surface water (e.g., rain or melting snow) or groundwater (e.g., springs or seeps).

What are Rivers, streams, and creeks?

Rivers, streams, and creeks are all types of flowing water on the Earth’s surface. These phrases are frequently used interchangeably to describe any kind of flowing water. Creeks are usually thought to be the smallest, streams the middle, and rivers the largest.

The majority of the water in rivers originates from precipitation that falls on the land and runs off into the river. Not all of this runoff, however, ends up in rivers. Some of it may evaporate before reaching the river, while others may be used for irrigation or other reasons by people.

Rivers often run through valleys in the terrain, separated by higher ridges of land. A watershed or drainage basin is an area of land that drains into a certain river.

The river receives the majority, but not all, of the precipitation that falls within a watershed. Some of it seeps into the earth and forms groundwater, which can then seep back into the riverbed.