What is a river basin? Types of river basins. Watershed concept

There are tens of thousands of rivers and streams on our planet. And each of them, even the smallest one, has a territory with which it collects its waters. In this article we will understand what a river basin is and what a watershed is. In addition, you will learn about the largest river basins of the Earth.

What is a river basin ?

Water, as we know, is in constant motion. Falling to the earth's surface in the form of precipitation, it flows from higher elevations to lower ones. Sooner or later, all this water is in a stream.

Small streams, merging, form small rivulets. Those, in turn, flow into larger channels. If you carefully consider the physical map of a territory, you will notice that all the rivers form a peculiar pattern on the surface of the Earth. In external outlines, it resembles a network of human blood vessels or a series of branched trees. Each of these “trees” is a separate river system. Now let's try to figure out what a river basin is.

In the figure below you can see an image of a classic river system. This is a diagram of a river basin. Here, the Roman river I shows the main river, and the numbers II - its tributaries. The territory outlined by the red dashed line will be the river basin for this water system.

So what is a river basin? This is the territory from which this or that system collects its waters. A river basin can also be called a drainage basin, or, even simpler, a drainage basin. All these terms refer to the same geographical concept.

What are river basins?

All river basins are divided into two types:

• sewage (the main rivers of which carry their waters to the oceans or seas);
• closed (the main rivers of which flow into bodies of water that are not connected in any way with the World Ocean).

River basins are also divided into:

• superficial;
• underground.

The surface parts of the river basin collect water and moisture, which accumulates on the surface of the earth, and the underground, respectively, from sources located underground. It is important to note that the size and boundaries of underground catchments are very difficult to determine. That is why hydrologists most often take into account only surface catchments when assessing and characterizing a particular river system.

The shape, shape and size of a particular river basin depend on many factors: the geographical position of the river system, topography, vegetation, geology, etc.

The largest river basins of the planet

The largest area on Earth is the Amazon basin, which occupies almost a third of the South American continent. It is also the largest in terms of watershed. It is followed by the river basins of the Congo (in Africa) and the Mississippi (in North America). The largest drainage basin of the planet is the Volga river basin.

The table below lists the ten largest river basins of the planet, indicating their area and geographic location.

What is a watershed?

If you go back to the diagram presented at the beginning of our article, you can see the red dashed line. This is the watershed - the border between the river basins.

To more clearly imagine what it is, it is enough to take a small oblong stone (preferably with a pointed peak) and pour water on it with a thin stream. You will see that one part of the poured water will drain to the ground on one side of the stone, and the other on the opposite.

Speaking in scientific terms, a watershed is a conditional line on the earth's surface that separates two (or more) neighboring watersheds and directs the flow of precipitation in opposite directions. By analogy with river basins, the watersheds are also divided into surface and underground.

Features and examples of watersheds

It is quite obvious that dividing lines in any locality should pass along its most elevated sections. So, in mountainous areas, as a rule, they pass along the ridges of ridges and individual peaks. On the plains, watersheds in the relief are weakly expressed. Here they very often represent rather large flat spaces, within which the direction of the water flow can periodically change.

Another important natural regularity: the higher the dividing line is, the higher and faster will be the speed of the water flow in all the rivers and streams that flow from it.

The main continent watershed dividing the catchment areas of different oceans is commonly called continental. In Russia, the largest watershed is the Valdai Upland. It is here that the largest European rivers originate: the Volga, Dnieper, Western Dvina. Another important watershed of Russia is the Ural mountain system. The rivers that flow down from its western slopes carry their waters to the Arctic Ocean. Watercourses flowing from the eastern slopes of the Urals later turn into the most important tributaries of the Ob - the largest river system in Siberia.