浙江义务教育初中自然一册讲述了水循环．海洋面上的水吸收热量，蒸发变成水蒸气．水蒸气上升到空中，随着气流运动，被送到陆地上空．在一定条件下，一部分水蒸气凝结，形成降水到地表．大气降水的一部分沿地面流动，构成地表径流；一部分渗入地下，形成地下径流．二者经过江 Zhejiang Compulsory Education Junior Middle School A book on water circulation. The water on the ocean surface absorbs heat and evaporates into water vapor. Water vapor rises into the air and is sent over land with the movement of air. Under certain conditions, a portion of the water vapor condenses to form precipitation to the surface. A part of the atmospheric precipitation flows along the ground and constitutes surface runoff; part of it seeps into the ground and forms underground runoff. Both pass through the river