When we are doing hydrographic studies we take into account the union of some rivers with others. Initially, when one or more rivers join, it is considered as tributary that river that has less importance. However, this has many exceptions as we will see throughout the article.
In this article we are going to tell you what a tributary is and what characteristics are considered to name a river that is a tributary of another.
What is a tributary
When one or more rivers join, normally, the smaller one is considered a tributary. The importance of one river or another lies in the size of the flow, the length or the surface of its account. The one with the least flow, length or a smaller count will be the tributary at a river junction. However, this is not always the case. We can see some examples such as the Mississippi River, whose tributary is the Missouri River and it is 600 kilometers longer and has a basin three times as long. To better understand the importance of rivers, it is useful to explore the facts and curiosities about the rivers of Spain, which highlight different aspects of the rivers in our environment.
We also find the Miño and Narcea rivers, which are shorter and have less flow than their tributaries, the Sil and the Nalón, respectively. All these exceptions show us that the importance of a river is almost always a matter of toponymy; that is, there is no irrefutable logic as to which river is the main river and which is its tributary. If you'd like to learn more about the main rivers in various regions, you can consult The main rivers of Valencia and their importance.
The terms used to indicate the status of the tributary in relation to the main flow are usually: Right or left tributary, left or right tributary. In this way we can know in which part the river of less importance is incorporated to that of greater. What these terms do is define, from the perspective of the waters that it gave, the lower slope in relation to the direction in which the river course is moving.
How are tributaries arranged?
When we talk about a main river and all its tributaries, we have to sort from those closest to the source of the river to those closest to the mouth. They are usually arranged in a hierarchyWe have first-order, second-order, and third-order tributaries. The first-order tributary is the smallest in size. The second-order tributary is composed of two or more tributaries that accompany the first order and combine to form it. The third-order tributary is the largest and most important. This classification is key to understanding the importance of tributaries in the hydrogeography of a given area.
Another way to order and organize the tributaries of a river is from the mouth to the source. In this way we will be giving it a dendritic structure. A more applicable way to use both methods is to divide them by sides: tributaries that arrive from the left or right as long as their head or source is in the direction of the mouth of the main river. This is a way of classifying the tributaries that have to do with the fluvial asymmetry of the rivers at the confluence of two or more of them. There are some rivers that flow into the main river after having traveled long distances.
It has always been said that the source of a river begins from the mountain and ends in the sea. This need not always be the case. In the case of rivers that are tributaries of other main ones, we find that the mouth does not end in the sea but in the bed of another river that feeds the flow. It is common to see rivers in the northern hemisphere whose main bank is to the left and forms a very sharp angle with their mouth. Most of the rivers that are tributaries of another by the right bank form an angle almost always right. All the exceptions are due to the characteristics of the relief.
What is an effluent?
Just as we have defined what an effluent is, we must say what an effluent is. It is precisely the opposite. It is a natural or artificial diversion that flows out of the main current of a larger river through a smaller one. In most cases, when a natural effluent occurs, it occurs in areas close to river deltas. There are also cases in which, because of the relief, it can also occur in other sections of the river. Some examples of them are the Casiquiare river with respect to the Orinoco river.
It's more common to see artificial effluents used to harvest water for agriculture and livestock farming. This creates a channel for supplying water to regions relatively far from the main river channel. Furthermore, effluents play an important role in water resource management.
Research and studies
In recent years, the possibility that the Amazon River may have some tributaries underground has come to light. These tributaries date back many years and travel for kilometers. A study conducted by Brazilian scientists has concluded that many years ago there was an underground river some 6000 kilometers long, located thousands of meters underground.
These studies will be carried out in different oil wells that have been used since the 70's. Thanks to the drilling it has been shown that there are movements 4000 meters below the riverThis underground river was named Hamza, named after the director of all the research, who may also have originated the idea that underground water movements could exist. He confirmed the existence of this river, and it can be stated with complete certainty that the entire Amazon rainforest is fed by water from two basins: the Amazon River and the Hamza River.
As you can see, a river's tributaries don't necessarily have to be strictly smaller, with a lower flow rate or a smaller bank size, but rather they depend on other determining factors. I hope that with this information you can learn more about what a tributary is and its importance for hydrogeography, as well as on aspects related to water management in different regions.
