What is the water cycle?
The water cycle is the continuing movement of water among oceans, atmosphere, land, ice, groundwater and living things. Water changes form and location; the cycle is not a single fixed route that proceeds everywhere at the same speed.
From evaporation to precipitation
Solar energy helps evaporate surface water. Plant transpiration adds water vapor to the air; the combined processes are studied as evapotranspiration. As moist air rises and cools, water vapor condenses onto tiny droplets or ice crystals, forming clouds. Growing droplets return as rain, snow or other precipitation. Not all rainfall reaches a river: some is caught by leaves, some infiltrates soil and some evaporates again.
Groundwater and human influence
Water infiltrating soil can pass through pores and recharge aquifers; runoff reaches streams, lakes and seas. Groundwater may remain stored for months, years or much longer, depending on its location. Snow and ice melt shape seasonal flow. Dams, irrigation, urbanization and groundwater pumping alter the amount and movement of water. Pollution can travel with water, so the continuing cycle does not mean water is clean or drinkable everywhere.