Different Processes in Water Cycle

Precipitation: Condensed water vapour that falls onto the earth’s surface. Most precipitation occurs as rain, but also includes snow, hail, fog, drip and sleet. Approximately 505,000 km³ of water falls as precipitation each year, 398,000 km³ of it over the oceans.

Canopy interception: The precipitation that is intercepted by plant foliage and eventually evaporates back to the atmosphere rather than falling to the ground.

Snowmelt: The runoff produced by the melting snow.

Runoff: The variety of ways by which water moves across the land. This includes both surface runoff and channel runoff. As water flows, it may infiltrate into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.

Infiltration: The flow of water from the ground surface into the ground. Once infiltrated, the water becomes soil moisture or groundwater.

Subsurface flow: The flow of water underground, in the vadose zone and aquifers. Subsurface water may return to the surface (e.g. as a spring or by being pumped) or eventually seep into the oceans. Water returns to the land surface at a lower elevation than where it infiltrated, under the force of gravity or gravity-induced pressures. Groundwater tends to move slowly, and is replenished slowly, so it can remain in aquifers for thousands of years.

Evaporation: The transformation of water from liquid to gas phases as it moves from the ground or bodies of water into the overlying atmosphere. The source of energy for evaporation is primarily solar radiation. Evaporation often implicitly includes transpiration from plants, though together they are specifically referred to as evapotranspiration. Total annual evapotranspiration amounts to approximately 505,000 km³ of water, 434,000 km³ of which evaporates from the oceans.

Sublimation: The state change directly from solid water (snow or ice) to water vapour.

Advection: The movement of water – in solid, liquid or vapour states – through the atmosphere. Without advection, water that evaporated over the oceans cannot precipitate over land.

Condensation: The transformation of water vapour to liquid water droplets in the air, producing clouds and fog.

Transpiration: The release of water vapour from plants into the air. Water vapour is a gas that cannot be seen