What is the river basin? Types of river basins. The concept of the watershed

On our planet - tens of thousands of rivers and streams. And each of them, even the tiniest, has a territory with which it collects its waters. In this article, we'll figure out 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 the river basin?

Water, as we know, is in constant motion. Falling to the surface of the earth in the form of precipitation, it drains from the more elevated parts of the relief to the lower ones. Sooner or later all this water is in some kind of watercourse.

Small streams, merging, form small rivulets. Those, in turn, fall into larger channels. If you carefully consider the physical map of any territory, you can see that all the rivers form a peculiar pattern on the Earth's surface. Outwardly it resembles a network of human blood vessels or a chain of branched trees. Each of these "trees" is a separate river system. And now let's try to figure out what the river basin is.

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

So, what is a river basin? This is the territory with which this or that system collects its water. The river basin can also be called catchment, or even easier - a catchment area. All these terms refer to the same geographical concept.

What are the river basins?

All river basins are divided into two types:

• Sewage (the main rivers of which carry their waters to the oceans or seas);
• Drainage (the main rivers of which flow into water bodies, not connected with the World Ocean).

River basins are also divided into:

• Superficial;
• Underground.

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

The shape, outlines and dimensions of a particular river basin depend on many factors: the geographic location of the river system, the relief, the vegetation cover, the geology of the terrain, and so on.

The largest river basins of the planet

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

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

What is the watershed?

If we return to the diagram presented at the beginning of this article, you can see the red dotted line. This is the watershed - the boundary between river basins.

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

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

Features and examples of watersheds

It is quite obvious that the watershed lines in any terrain must pass along the most elevated parts of it. So, in mountainous areas, as a rule, they pass along ridges of ridges and separate peaks. On the plains the watersheds in the relief are poorly expressed. Here they very often represent fairly large areas of flat space within which the direction of the water flow can change periodically.

Another important natural pattern: the higher the water dividing line, the higher and more rapid the rate of water flow in all the rivers and streams that flow from it.

The main watershed of the continent, dividing the catchment basins of different oceans, is usually called continental. In Russia, the largest watershed is the Valdai Upland. It is here that the largest European rivers originate: the Volga, the Dnieper, the Western Dvina. Another important watershed of Russia is the Ural mountain system. The rivers that drain 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 River - the largest river system in Siberia.