Human life has always been closely connected with rivers. This was not only in the past, there is such a connection today. People always built their first settlements on the banks of reservoirs, closer to sources of fresh water. They were used for fishing and irrigation, as means of communication, timber was rafted along them. Today, all the major cities of the world are located on large rivers, and their names sound like synonyms: London and the Thames, Paris and the Seine, St. Petersburg and the Neva, New York and the Hudson.
Ever since school, we all know what a river is, as well as the fact that this water flow moves in a depression called a channel. Each of them, like everything in this world, has a beginning, it is called a source. And the place where it flows into the sea, ocean or lake is called the mouth.
The water stream can also flow into another, larger one. The main channel with all tributaries form a river system.
Each river, regardless of size, has its own basin - a certain area from which it collects surface and groundwater. The boundary separating the basins is called the watershed.
When talking about what a river is, it is necessary to mention its mode. The supply of surface and ground waters, as well as the discharge, occurs unevenly throughout the year. As a result, the water level in the channel and other indicators change seasonally.
The mode usually has several periods. Everyone saw what a river is in high water - this annual recurring flood at the same time cannot be overlooked. The water level in the channel rises so much that it overflows the banks. Another period, the low water period, is equally pronounced. At this time, the water level is the lowest, which is caused by a decrease in its flow from the catchment area. And then there are floods - a sudden rise in the level caused by heavy rainfall or too rapid snowmelt.
What are they like
Depending on the landforms through which they flow, water flows are divided into two groups:
The flow of rivers on a flat surface is slow, since their sources are at a low height, and the slope of the terrain through which they flow is small. Their valleys are wide, with sloping slopes. An example is the great rivers of China: the Yangtze and the Yellow River. The Volga, Dnieper, Don and others known to us also belong to the same group.
In the mountains, the current is very fast, since the sources are located high, and the mouths are on the plains. The slope of the territory is significant, the water in the channel moves at high speed, "cutting through" in solid rocksfor hundreds of thousands of years, narrow valleys with steep slopes. What is a river flowing in the mountains? This is strength and power, an unstoppable stormy stream rushing along the rifts and rapids. Perhaps the most prominent representative of this group is the Yenisei.
Frequently, streams that start in the mountains, leaving the plane, change their character, turning from mountainous into flat ones. Some rivers of Bashkiria, whose sources are located on the western slopes of the Ural Mountains, can serve as an example. The main water artery of this republic is the river. Belaya, along the picturesque banks of which cities and towns are located. Descending from the mountain spurs, flowing along the Ural Plain and collecting the waters of numerous tributaries on its way, it becomes sedate and navigable.