Drainage basins in the context of "Dead zone (ecology)"

A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it runs out of water, or only flow during certain seasons. Rivers are regulated by the water cycle, the processes by which water moves around the Earth. Water first enters rivers through precipitation, whether from rainfall, the runoff of water down a slope, the melting of glaciers or snow, or seepage from aquifers beneath the surface of the Earth.

Rivers flow in channeled watercourses and merge in confluences to form drainage basins, areas where surface water eventually flows to a common outlet. Drainage divides keep rivers separated from other courses of water and causes upstream water within the confines of the divide to fall into the downhill stream. Rivers have a great effect on the landscape around them. They may regularly overflow their banks and flood the surrounding area, spreading nutrients to the surrounding area. Sediment or alluvium carried by rivers shapes the landscape around it, forming deltas and islands where the flow slows down. Rivers rarely run in a straight line, instead, they bend or meander; the locations of a river's banks can change frequently. Rivers get their alluvium from erosion, which carves rock into canyons and valleys.

The Polesian Lowland is a lowland in the southwestern portion of the East European Plain in the drainage basins of several rivers including the Dnieper, Pripyat and Desna. It stretches along the Belarus–Ukraine border. It basically defines the historical region of Polesia.

It is politically split into the Belarusian Polesia [be] in the south of Belarus, Ukrainian Polissya [uk] in the north of Ukraine (where Волинське, Рівненське, Житомирське, Київське Полісся are distinguished), the eastern part of the lowland extends into Bryansk Oblast in the Russian Federation, and the western part extends into Poland.
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