地球的“血液循环” 地球上的水连续不断地变换地理位置和物理形态(相变)的运动过程,称为水分循环,又称水循环或水文循环。水的三态转化特性是产生水分循环的内因,太阳辐射和重力作用则是水分循环的动力。在一定时期内,地球上的水分收入、支出总量基本保持平衡。 根据水分循环的过程可将自然界的水分循环分为大循环和小循环两种类型。大循环,就是从海洋上蒸发的水汽被气流带到大陆上空,在适当的条件下凝结,以降水的形式降落到地表。降落到地面的水一部分可以形成地表径流;一部分可为植被拦截或被植物散发。渗入地下的水一部分以表层壤中流和地下径流形式进入河道,成为河川径流的一部分,而贮于地下的水则一部分上升至地表供 Earth’s “blood circulation” Earth’s water on the planet continuously transform the physical location (physical transformation) and the movement process, known as the water cycle, also known as the water cycle or hydrological cycle. Three-state conversion of water is the internal cause of the water cycle, solar radiation and gravity is the driving force of the water cycle. In a certain period of time, the total income and expenditure on the Earth’s water basically keeps the balance. According to the process of water cycle can be divided into the nature of the water cycle and the cycle of small cycles of two types. The great cycle, that is, the water vapor that has evaporated from the ocean, is carried by the air currents over the continent and condenses under proper conditions and falls to the surface in the form of precipitation. Part of the water landing on the ground can form surface runoff; some can be intercepted by vegetation or emitted by plants. Part of the water that has infiltrated the subterranean stream enters the river channel as surface soil inflow and underground runoff and becomes part of the runoff from the river, while part of the underground water rises to the surface