River

But where, as a river in such a case, receive such an unlimited supply of water? Where she takes her "vechnotekuschuyu" water? And here in the first place to look at the source of the river, its onset. Part of the river begin where groundwater reaches the surface. This may be a mountain slope or hill, ravine, swale. Alpine same river often begins at the bottom of glaciers. Typically, even large rivers are formed from small streams. Some exceptions are rivers that flow from the lakes. Those rivers in Eurasia are Neva, Ron, Angara. But the river need more and nutrition. It may be different: rain, snow, ice, or underground. Yet mostly they are the primary source of precipitation: On land, an annual fall of about 108,000 cubic kilometers of precipitation. Of these, 35.4 drains into the ocean by rivers, and about three goes into the ocean from glaciers in Greenland and Antarctica, and the rest simply evaporates. On his way flow of the river gathers itself and by the tributaries of atmospheric precipitation with a vast territory. This area is called catchment basin. A quantity of water that the river makes the seas and oceans for the year is called the river runoff. There is another dimension that apply to river water. This amount of water flowing through the cross section of the river in one second. It bears the name of the river flow. Stock may change annually. After all, it depends on the falling of rain per year. A flow of the river varies throughout the year. Above all, it happens during the flood and flood. Flood - a long-level rise in the river, which is called the main source of its power. He repeated annually in a certain season. Flooding - a relatively short-term uplift of water, which occurs after prolonged rains or short, but heavy rain squall. Longer flooding happens in spring, after the melting of snow and ice in the rivers. Therefore, floods, and floods sometimes lead to catastrophic flooding. They flood the villages and cities, lead to the destruction of homes, destroyed crops and washed away the top layer of fertile land. When rain floods in the rivers feeding occurs during the rainy season. If the food snowy, then the flood comes the spring after the snow melts. With glacier flood occurs in the summer. In rivers, which start on the slopes of high mountains, there are two flood. The first occurs in the spring after snowmelt and the second - in the summer, when melting glaciers. The water level in the river after a flood incident. This period is called the low water. In the tropics, the rivers are short and the long period of high water low water. In temperate and northern latitudes to the flood and is replaced by low water in rivers is added, even winter, when they were pinned down by ice. At this time the water level in the river is usually low. Rivers on earth a great many. But we see only some of which have not only a geographical significance, but related, and influenced the formation and development of civilizations.