The Water Cycle

No Beginning... No End

The water cycle has no starting point.

But, we can start with the oceans, since that's where most of Earth's water exists.

The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air.

Ice and snow can sublimate directly into water vapor. Rising air currents take the vapor up into the atmosphere, along with water fromevapotranspiration, which is water transpired from plants and evaporated from the soil.

The vapor rises into the air where cooler temperatures cause it to condenseinto clouds.

Air currents move clouds around the globe, cloud particles collide, grow, and fall out of the sky as precipitation.

Some precipitation falls as snow and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years.

Snowpacks in warmer climates often thaw and melt when spring arrives, and the melted water flows overland as snowmelt.

Most precipitation falls back into the oceans or onto land, where, due to gravity, the precipitation flows over the ground as surface runoff.

A portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans.

Runoff, and ground-water seepage, accumulate and are stored as freshwater in lakes.

Not all runoff flows into rivers, though.

Much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes aquifers(saturated subsurface rock), which store huge amounts of freshwater for long periods of time.

Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as ground-water discharge, and some ground water finds openings in the land surface and emerges as freshwater springs.

Over time, though, all of this water keeps moving, some to reenter the ocean, where the water cycle "ends" ... oops - I mean, where it "begins."

Aquifers and Groundwater
Large amounts of water are stored in the ground; Thus, the name "groundwater."

Clouds (water vapor)
Water stored in the atmosphere as vapor; we call it clouds and humidity.

Condensation
When water changes from vapor into liquid, it's called condensation.

Evaporation
Evaporation from the oceans is the primary mechanism supporting the surface-to-atmosphere portion of the water cycle.

Evapotranspiration
The process by which water vapor is discharged to the atmosphere as a result of evaporation from the soil and transpiration by plants is defined by the USGS as evapotranspiration.

Fresh Water
Fresh water is essential to all life on the planet.

Ice and Glaciers
During the last ice age (when glaciers covered more land area) the sea level was about 400 feet lower than it is today.

Infiltration
The downward movement of water from the surface into soil, porous rock, and aquifers, is known as infiltration.

Oceans
More than 95% of the world's water is stored in oceans.

Precipitation
Precipitation is Nature's delivery system for getting water vapor to the Earth.

Snowmelt Runoff
We don't get much run-off due to snowmelt here in Blanco, Texas. But hey- almost anything is possible.

Springs
Springs are a lot more common in limestone - which we have in abundance -than other varieties of rock.

Stream Flow
Streamflow is defined as the natural movement of water in rivers, creeks, and streams.

Sublimation
When describing the water cycle, sublimation refers to the process of snow and ice changing into water vapor without first melting into water.

Surface Runoff
Much of the water in the Blanco River comes directly from surface runoff.

Back to Blanco Water Issues

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