The Water Cycle

• Water comes from primordial Earth, condensed from magma as Earth cooled.

• Water cycle is driven by the sun and by gravity.

• Necessary for life on Earth. Without it, water would become stale and polluted very quickly.

Let’s start with the Oceans

• 1,338,000,000 km3 water stored in oceans. That’s almost 97% of all the water!

• About 90% of the evaporated water going into the water cycle comes from the oceans.

Water is EVAPORATED*• Evaporation requires energy… this is where the

sun comes into play.• It takes in energy (endothermic) which is why

water on your skin cools you (unless it is too humid).

• Once evaporated, a drop spends about ten days in the air

• Water even evaporates at freezing!

Transpiration

• Plant gives off water vapor through pores in leaves.

• 10% of the H2O in the atmosphere comes from transpiration.

• A large oak tree can transpire 40,000 gallons/year!

THE WATER VAPOR SUPERHIGHWAY

• Water vapor CONDENSES to form droplets, and eventually clouds.

• Clouds are the most visible sign, but even clear air has water in it.

• 12,900 km3 of rain, which isn’t really a lot--- if it all rained at once, the entire ground would be covered with only about 1 inch.

On average, contiguous United States (CONUS) receives enough rain each year to cover the

ground 30 inches deep!

Reservoirs of Land Water

• Ice Caps–90% of Earth’s ice is in Antarctica. –In Greenland the ice is so heavy

that the ground (about 5000 feet under) is pressed into the shape of a bowl.

Glacier Reservoirs

• Cover 10-11% of the land.• If all glaciers melted, the seas would rise

230 feet.• During the last ice age, the sea levels

were 400 feet lower than they are now.• During the last warm era, the sea levels

were 18 feet higher.

Rivers• Basically, the transport of water from point A to point

B.• Much of the water that rivers transport comes from

snow melt.• Watershed is the area of land where all the surface

runoff drains into one river.

Freshwater Storage

• Only about 3% of all water on Earth is Fresh, 0.29% of it is lakes and swamps.

• 20% of fresh water is all in Lake Baikal– Compared to the Great Salt Lake…

Great Salt Lake has about 37 km3 of water.Lake Baikal has about 5700 km3!

Springs

• Formed when an underground water source intersects with a hill or a valley

Subsurface Water

• Large amounts of water are underground, moving, sometimes very slowly.

Thermal Springs

• Some are fed by volcanic activity underground.

• Others have flow that go far underground and then come back up quicker.

All is driven by the SUN!