THE WATER CYCLE THE EXISTENCE AND MOVEMENT OF WATER ON, IN, AND ABOVE THE EARTH.

The Earth’s water is always in motion. The Earth’s water is always changing states: gas (vapor) to liquid to solid (ice) and back again. The Sun is the driving force behind the water cycle!

The water cycle has no starting point, but we'll begin in the oceans, since that is where most of Earth's water exists.oceans 1.The sun (which drives the water cycle) heats water in the oceans. Some of it evaporates as vapor into the air;evaporates A relatively smaller amount of moisture is added as ice and snow sublimate directly from the solid state into vapor.sublimate 2.Rising air currents take the vapor up into the atmosphere, along with water from transpiration.atmospheretranspiration 3.The vapor rises into the air where cooler temperatures cause it to condense into clouds.condense Evapotranspiration & Condensation Transpiration is essentially the evaporation of water from plant leaves and from animals.

4.Air currents move clouds around the globe, and cloud particles collide, grow, and fall out of the sky as precipitation.precipitation Some precipitation falls as snow and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years.ice caps and glaciers 5.Most precipitation falls back into the oceans or onto land, where, due to gravity, the precipitation flows over the ground as surface runoff.surface runoff A portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans.streamflow Runoff, and groundwater seepage, accumulate and are stored as freshwater in lakes.stored as freshwater Not all runoff flows into rivers, though. Much of it soaks into the ground as infiltration.infiltration 6.Over time, all of this water keeps moving, some to reenter the ocean, where the water cycle “ends.” Precipitation & Runoff

Only 2.5% of Earth’s water is freshwater. Only 1.3% of Earth’s freshwater is on the surface, not in glaciers or ice caps Only 20.5% of Earth’s surface water is in rivers, streams, and lakes. What percent of all of Earth’s water is stored in freshwater lakes and rivers above ground?

Freshwater: Glaciers Glaciers are formed through precipitation, as layers of snow continually fall in an area and stay in solid form for a LONG time. Iceburgs are “calved” (formed) when large chunks of ice cleave off of a glacier and fall into the ocean.

Freshwater: Surface Water The area of land that contributes water to a river system is called a watershed. Surface water runs downhill, eventually reaching the ocean. Q: Why does water run downhill?

Once in the ground, some water travels close to the land surface and emerges very quickly as seepage into streambeds. Due to gravity, much of the groundwater continues to sink deeper into the ground. Freshwater: Groundwater Water table: the level below which the ground is saturated with water. An aquifer is an underground layer of water-bearing substrate from which groundwater can be extracted using a water well. A spring is any natural situation where water flows from an aquifer to the earth's surface.