Some tributaries are little more than a trickle.
Tributaries are the arms of a river, beginning at the top of a basin and slowly descending to join other tributaries and eventually the main river, which empties into the sea. Tributaries come in a wide variety of shapes and sizes, and the study of tributaries is of interest to some biologists because they can be used to trace pollution and various living organisms such as alien invaders back to their origins. You can see the tributaries on a map; look for the characteristic opening of a river in the sea and then trace it inland. All the small arms that appear are tributaries.
The word “tax” comes from the same root as “tribute”. Both words come from the Latin tribuere, when it means “to distribute or distribute”. In a sense, tributaries can be said to bring tribute from the far reaches of a basin to the river.
As the tributaries meet, they get larger.
Rivers are designed to drain watersheds, areas of land that are surrounded by hills and mountains, creating a watershed. Watersheds are also called “drainage basins.” The network of tributaries that combine to form a river is linked to numerous water sources in a basin, from areas that flood in winter to glaciers that melt in summer. Without tributaries and rivers, watersheds would slowly flood.
Some tributaries are little more than drops on the ground, while others are sizable rivers and streams. They all drain the water, along with any substances that may have dissolved in the water, such as sludge, decaying organic matter, and pollution from places like farms, sewage treatment plants, and businesses built along the banks of the tributary.
As the tributaries meet, they get progressively larger, until they reach the main stem of the river. Along the way, sediment moves out of the water, leaving behind a rich, fertile layer of silt, along with any other material the tributary may have accumulated. Eventually, the water reaches the ocean, where it will flow along with global currents, evaporate, and eventually start the cycle all over again.
Many nations have faced serious water pollution as a result of increasing industrialization and human population. Biologists often use tributaries to identify sources of pollution; For example, if a river is experiencing an algal bloom, biologists may try to isolate the section of the river where the bloom is occurring before testing the tributaries in that section to try to find the nutrient source that is causing the bloom. Traveling along the tributary can reveal something like a manure leak on a pig farm or fertilizer runoff from a farm.