- continuous movement of water through Earth’s systems
- stages: evaporation, condensation, precipitation, runoff, collection
- driven by solar energy and gravity
- evaporation from oceans and land surfaces lifts water into the atmosphere
- condensation forms clouds, precipitation returns water as rain, snow, sleet, hail
- runoff flows through rivers and streams to lakes and oceans
- groundwater infiltration recharges aquifers through soil and rock
- transpiration from plants returns water to the atmosphere
- the cycle purifies water, distributes heat, and shapes biomes
- connected to carbon cycle and nitrogen cycle through dissolved transport
- glaciers and ice caps store 69% of Earth’s freshwater