Water moves among reservoirs above, on and below Earth's surface.
Key knowledge
The water cycle describes water storage and movement among the atmosphere, surface and subsurface. Water can be liquid, solid or gas. Solar energy and gravity drive its movement, while human activities alter storage, flow and water quality.
Conditions and scope
Reservoirs and pathways have different residence times; the cycle is not one uniform loop.
This entry does not quantify local water availability or purity.
Sources · 3
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
USGS's documented reservoir, phase, driver and human-influence overview; no local hydrological measurement.
2026-10-10 · English hydrologic scope checked against the direct USGS water-cycle FAQ.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Agreement within this scope
Water phase changes, solar-driven evaporation and surface/subsurface storage.
Water moves through several linked stores, not just a rain–evaporation loop.
The water cycle describes water storage and movement among the atmosphere, surface and subsurface. Water can be liquid, solid or gas. Solar energy and gravity drive its movement, while human activities alter storage, flow and water quality.
At the top of the atmosphere, Earth's radiative balance compares incoming sunlight with reflected sunlight and outgoing thermal radiation. On a global average, sustained net energy input increases energy stored in the Earth system; radiative equilibrium requires balanced incoming and outgoing fluxes.
Solar energy drives water movement and evaporation transfers energy within the Earth system.
Glacier accumulation and ablation determine a mass budget; an equilibrium line separates zones in the specified surface-balance picture. Ice moves through deformation and, where conditions permit, basal sliding. Terminus advance or retreat reflects both mass balance and ice transport, so retreat does not mean all ice flows uphill.
Water-vapour amount and relative humidity are distinct; relative humidity compares vapour pressure with a specified saturation value at the current temperature. Cooling an air parcel can bring it toward saturation. Ordinary cloud-droplet formation depends on suitable aerosol nuclei, supersaturation and ongoing condensation/evaporation as parcels mix and move.
Condensation participates in atmospheric water exchange.
A surface-water drainage basin, catchment or watershed is the land area contributing surface drainage to a specified outlet. Neighboring basins are separated by drainage divides, commonly associated with topographic high ground. Changing the outlet changes the basin; smaller basins can nest within larger ones. Infiltration, storage and evaporation mean precipitation does not all immediately become streamflow. Groundwater divides describe subsurface flow systems and need not coincide with surface-water divides.
The selected outlet organizes part of the water cycle, with infiltration, storage and atmospheric exchange affecting the basin budget.