Human life has always been closely associated 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 fresh water sources . They were used for fishing and irrigation, as a means of communication, they rafted the forest. 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.
From school, we all know what a river is, as well as how this water stream moves in a depression called a channel. Each of them, like everything in this world, has a beginning, it is called the source. And the place where it flows into the sea, ocean or lake is called the mouth.
Water flow can also flow into another, larger in size. The main channel with all its tributaries forms a river system.
Each river, regardless of size, has its own pool - a specific area from which it collects surface and groundwater. The border dividing the basins is called the watershed.
Mode and power
Talking about what a river is, it is necessary to mention its regime. The supply of surface and groundwater, as well as consumption, occurs unevenly throughout the year. As a result, the water level in the channel and other indicators change seasonally.
In a mode, several periods are usually allocated. What a river is in flood, everyone has seen - this annually repeated spill at the same time cannot be overlooked. The water level in the channel rises so much that it overflows the coast. Another period is equally pronounced - low water. At this time, the water level is the lowest, which is caused by a decrease in its flow from the catchment area. And there are still floods - a sudden rise in the level caused by heavy rainfall or too fast snowmelt.
What are they
Depending on the landforms along 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 an insignificant height, and the slope of the terrain along 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.
In the mountains, the current is very fast, since the sources are high, and the mouth is on the plains. The slope of the territory is significant, the water in the channel moves at high speed, "cutting" narrow valleys with steep slopes in hard rocks for hundreds of thousands of years. What is a river flowing in the mountains? This is strength and power, an uncontrollable
stormy stream rushing along the rifts and rapids. Perhaps the most striking representative of this group is the Yenisei.
Often the streams that begin in the mountains, going out onto the plane, change their character, turning from mountain to plain. An example is some of the rivers of Bashkiria, whose sources are located on the western slopes of the Ural Mountains. The main waterway of this republic is r. Belaya, on the picturesque shores of which cities and towns are located. Going down from the mountain spurs, flowing along the Ural plain and collecting water of numerous tributaries on its way, it becomes sedate and navigable.