Placeholder Image

Subtitles section Play video

  • MUSIC

  • ANNE THOMPSON: All the water on Earth today, every drop, is all

  • the water there has ever been on the planet. Freshwater is

  • actually millions of years old. The same water, flowing in a

  • continuous loop- falling as rain and snow from clouds to the

  • Earth's surface, running in rivers, pooling in ponds,

  • flowing from faucets, irrigating crops, traveling through plants,

  • generating power, eventually evaporating into the air and

  • condensing into clouds again.

  • ANNA MICHALAK: Why is there life on Earth? The reason

  • there is life on Earth is because Earth has this

  • perfect water cycle.

  • THOMPSON: The Water Cycle, so simple even small children

  • understand the basics, yet so complex, the most advanced earth

  • scientists, hydrologists, geologists, and biogeochemists

  • are studying every part and process.

  • MARTHA CONKLIN: The Water Cycle is fascinating. It's something

  • that's around us all the time, and yet we don't

  • really understand it.

  • THOMPSON: How to summarize what is known about the Water Cycle?

  • With two words- flows and stores. The Water Cycle is a

  • series of flows of water between various water stores or

  • storages. Clouds in the atmosphere...

  • TOM HARMON: There's always a little bit of water in the

  • atmosphere. We talk about relative humidity- it's a humid

  • day, it's a dry day- either way, there's water, sometimes a

  • little, sometimes a lot.

  • THOMPSON: There's a lot of water in the oceans – 70% of all

  • the water on Earth, in the ice sheets and glaciers - two-thirds

  • of all the fresh water on Earth, in the snow packs atop mountains

  • like the Sierra Nevada, in the Great Lakes, in rivers and

  • streams, in reservoirs and watersheds, in wetlands, in the

  • soil, in and on plants and trees rooted in the soil, and beneath

  • the soil, in water tables and underground aquifers like the

  • Ogallala-High Plains, which runs underneath parts of eight

  • states, from South Dakota to Texas. All this storage is

  • temporary. Water, in all its forms, is always in flux and

  • always moving. And there's a name for every kind of movement

  • in the Water Cycle starting with precipitation.

  • MICHALAK: Precipitation is the process of water falling onto

  • the surface of the Earth. You can have precipitation in many

  • forms- rain, snow, hail.

  • THOMPSON: Rain is falling water in liquid form. Snow,

  • ice, hail and sleet are falling water in solid, or frozen form.

  • Fog and mist? Falling water in gas or vapor form. Precipitation

  • that falls directly into the oceans becomes part of surface

  • ocean and can be churned by wave and wind action into ocean

  • currents. Rain and snow that falls directly on rivers and

  • streams becomes one part of stream flow. Rain that falls

  • onto land takes a different path to the river as does the

  • snow and ice that falls and collects on mountaintops

  • when temperatures warm.

  • CONKLIN: When snow melts, some of it runs through the snowpack

  • and goes into small streams, tributaries that feed

  • into large rivers.

  • THOMPSON: What about the precipitation that falls on and

  • over land? Some is intercepted by vegetation -

  • plants and trees.

  • HARMON: Like you might imagine, someone in a game of football

  • intercepting a pass, these are raindrops trying to come to the

  • ground, and leaves on the tree intercept them before they

  • hit the ground.

  • THOMPSON: And the precipitation that does hit the ground? It can

  • run off if the ground is hardscaped - covered with

  • asphalt or concrete- or if the soil is too wet, or saturated to

  • absorb more water, like an over soaked sponge. Otherwise,

  • precipitation infiltrates the soil surface, percolates

  • into the ground.

  • HARMON: Think of it as the water percolating through your

  • coffee grounds in the morning. Gravity continues to pull it

  • downwards so it will move through.

  • THOMPSON: Through the topsoil, into spaces between soil and

  • rock particles, down to bedrock, and further, into fractures,

  • into deep underground aquifers. Even groundwater here

  • is moving sideways, or laterally, discharging toward a

  • river, lake or the sea, generally the deeper the flow,

  • the slower the flow.

  • CONKLIN: Some of that fractured water might take a very long

  • time, thousands to millions of years, to get out.

  • THOMPSON: And how does water get back out into

  • the atmosphere? It evaporates, is turned from a liquid

  • into a gas or vapor, by the heat of the sun.

  • MICHALAK: If you put a bit of water into a bowl and you set it

  • outside on a sunny day, it's going to disappear. It's still

  • water, it's just in the form of a gas rather than in the form

  • of a liquid.

  • THOMPSON: Water evaporates from every wet surfaceeven from

  • wet air. Some rain and snow evaporates into the air while

  • falling. Water evaporates through our respiration and

  • perspiration and from plants, through transpiration. Trans

  • means through or across. Plant roots draw up groundwater.

  • MICHALAK: And plants pull that water up through their stems

  • into their leaves and then release it back out

  • through evapotranspiration.

  • THOMSPON: Evaporanspiration, a spelling bee worthy term for

  • evaporation from soil and water surfaces, plus transpiration

  • from plants. Evaporated water molecules are tiny enough to

  • flow into the air. Mix with smoke and dirt particles in the

  • atmosphere. Cool, condense, into visible masses of water vapor

  • clouds. Winds move clouds into colder air, water droplets

  • collide and merge, grow bigger and heavier, until they

  • are so heavy, they fall again as rain or snow, sleet or hail.

  • Precipitation. Collection. Runoff. Interception.

  • Infiltration. Percolation. Discharge. Transpiration.

  • Evaporation. Condensation. The Water Cycle.

  • MUSIC

MUSIC

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

B2 water thompson precipitation water cycle soil cycle

The Water Cycle

  • 466 34
    nini posted on 2014/11/24
Video vocabulary