water cycle(redirected from water cycles)
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the continuous migration of water on earth (in its atmosphere, hydrosphere, and crust), accompanied by phase transitions of the water and possessing a more or less pronounced cyclical character.
The water cycle consists of the evaporation of water from the underlying surface and its transport by air currents from the evaporation site, condensation of water vapor, precipitation, and shifting of water in bodies of water over the land surface and within the earth’s crust. Most of the water evaporates from the oceans and returns to them; less is transported by air currents from the oceans to land. The transport of moisture evaporating from land to the oceans by air currents is slight. The water cycle is characterized quantitatively by the water balance.
A small cycle—sea (ocean) → atmosphere → sea (ocean)— and a large cycle—ocean → atmosphere → land — ocean—are distinguished according to the site of the evaporation and precipitation of water and the modes of its transport. Moisture repeatedly evaporates from the continents, is transported in the atmosphere, condenses, and again falls in the form of precipitation and again evaporates. This complex of processes is called the intracontinental cycle. An internal moisture cycle is characteristic of closed intermontane basins. The water cycle on the earth is part of the total complex of processes participating in the cycle of matter on the earth. (See alsoHYDROLOGIC CYCLE.)
K. G. TIKHOTSKII