The Water Cycle

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The Water Cycle

• Investigative Science

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Water Cycle Jump Video

• Water Cycle Jump

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Water

• 3 states
• Solid
• Liquid
• Gas
• The 3 states of water are determined mostly by
  temperature.
• Even though water is constantly changing states,
  the total amount of water on Earth remains
  constant.
• Over 70 of the Earths surface is covered by
  oceans
• Water is constantly being cycled between the
  atmosphere (air), hydrosphere (water), and
  lithosphere (land).

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Evaporation

• The sun (temperature) is the energy force that
  powers the water cycle
• It heats oceans, lakes, rivers and causes water
  to change from the liquid state to the gaseous
  state
• The oceans contribute to about 80-90 of the
  water vapor in the atmosphere.
• During evaporation, the impurities (for example,
  Salt) are left behind.
• This is important because about 97 of the water
  on Earth is salt water (oceans) and only 3 is
  freshwater (rivers, streams, lakes, ponds, and in
  the ground).

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Condensation

• When atmospheric temperature decreases, the water
  vapor (gas) changes back into a liquid.
• Condensation is the opposite of evaporation.
• Small water droplets are formed in the
  atmosphere.
• Collections of water droplets form clouds in the
  sky or fog at ground level.
• You can see condensation on drinks in the
  summertime or leaves in the morning.

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Precipitation

• Tiny water droplets bounce around in a cloud and
  as they hit each other, they stick together and
  become larger.
• The clouds get heavy and eventually water falls
  back to the Earth.
• Precipitation can occur in the form of rain,
  freezing rain, sleet, snow, or hail.
• Most precipitation falls back into the oceans or
  onto land. If precipitation falls in the form of
  snow it can accumulate in the form of ice caps or
  glaciers.
• Most of the condensed water in clouds does not
  actually fall as precipitation.

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Surface Runoff

• About 1/3 of the water that returns to the Earth
  as precipitation runs off the surface of the
  land, down hill, into streams, rivers, lakes, and
  oceans.
• The other 2/3 of precipitation is evaporated,
  transpired, or is infiltrated into ground water.
• Surface Runoff is a very important part of the
  water cycle because it returns water once again
  to the bodies of water, where evaporation occurs.
• For example, when snow melts

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Infiltration

• Not all surface runoff water flows back into
  streams, rivers, lakes, and oceans. Some of it
  soaks into the ground.
• Infiltration is the downward movement of water
  from the land surface into soil or underlying
  rock layers.
• This water can replenish aquifers, which store
  large amounts of freshwater that can be removed
  from the ground using a water well.
• Some infiltration stays close to the land
  surface and can seep back into surface-water
  bodies
• (and the ocean) as
• groundwater discharge.
• Some groundwater finds
• openings in the land surface
• and comes out as
• freshwater springs.

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Transpiration

• Water is returned to the atmosphere by plants.
• Water is absorbed by plants (usually through the
  roots) from water that is in the soil.
• The water travels up through the plant and then
  is evaporated back into the atmosphere from the
  plant surface (usually the leaves).

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Sublimation

• Sublimation is the conversion between the solid
  and gaseous form of water, with no intermediate
  liquid stage.
• This occurs when there is low atmospheric
  pressure.
• An example of this is when snow and ice change
  into water vapor in the air without first
  melting into water.

Phase Diagram for Water
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