Water Cycle — Definition

Definition

The water cycle is the continuous movement and storage of water among the atmosphere, land, oceans and subsurface. Water changes location and sometimes physical state through evaporation, transpiration, condensation, precipitation, runoff and subsurface movement.

The cycle is a network of pathways and stores, not a single route followed by every water molecule. Some water returns rapidly to the atmosphere; some remains stored much longer. Understanding the cycle helps explain why rainfall, groundwater recharge and river flow are connected but not identical quantities.

Human withdrawals, reservoirs, land cover and pollution can alter pathways, timing and quality without creating a separate cycle outside nature.