The Water Cycle

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The Water Cycle
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Arguably the most important natural phenomenon
on Earth, the water cycle, also known as the
hydrologic cycle, describes the constant movement
and endless recycling of water between the
atmosphere, land surface, and under the ground.
The hydrologic cycle supplies the force needed
for most natural processes, thus supporting life
itself.
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The Water Molecule

• H20 consists of one atom of oxygen bound to two
  atoms of hydrogen. The water molecule has a
  positive charge on the side of hydrogen atoms and
  a negative charge on the other side. Water
  molecules tend to attract each other because the
  positive ends attract to the negative ends.

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• Water is a universal solvent and wherever it
  goes throughout the water cycle, it takes up
  valuable chemicals, minerals and nutrients.

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Condensation

• The change from a liquid to a gas. In the water
  cycle, the change from water to water vapor.

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Condensation Convection

• Warm air rises
• Air cools and can no longer hold vapor
• Process known as CONVECTION

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Condensation Cloud Formation

• Cooling of water vapor forms CLOUDS
• Other ways clouds are formed
• Convergence
• Lifting of air by fronts

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Precipitation

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Snow

• Snow is a type of precipitation like rain but at
  cooler temperatures
• Usually reaches the ground and stays
• Eventually melts and becomes runoff in streams

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Rain

• Type of precipitation during warmer weather
• Occurs when clouds become too full
• Falls to earth in the form of water and runs off
  to streams rivers

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Freshwater Storage

• Water may be stored temporarily in the ground,
  oceans, lakes, rivers, and glaciers.

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• The worlds two main reservoirs of fresh water
  are the great polar ice caps, and the ground.
• If all of the ice in the ice caps and other
  glaciers melted, it would raise the sea level by
  about 260 ft.

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• In temperate climates, water is found in surface
  water puddles, ditches, and anywhere else that
  runoff water can gather. This is a temporary form
  of storage

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Freshwater Flow
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• A hydrologist is particularly interested in
  stream flow -- the 31 of precipitation which
  runs off into rivers, streams and lakes.

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• About 3 of this water will seep underground
• About 31 will run off into rivers, streams and
  lakes
• About 66 of the water returns to the atmosphere
  through evaporation and transpiration

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Surface Runoff

• When precipitation rate exceeds infiltration
  rate, or when soil is saturated, water begins to
  move down slope on ground surface.

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Surface Runoff

• surface runoff gradually flows into gullies,
  streams, lakes, or rivers. Water in streams and
  rivers flows to the ocean, seeps into the ground,
  or evaporates back into the atmosphere.

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• The largest reservoir is the oceans. There is
  about 50 times as much water in the oceans than
  in the next largest reservoir, polar ice and
  glaciers.

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Water Storage in Ice and Snow
Water precipitates into cooler areas of land and
freeze into ice and snow.
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Snowmelt Runoff to Streams

• Precipitation falls in the form of rain and snow
• When the snow melts it runs into streams which
  eventually dump into the ocean

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Infiltration
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-Rain water soaks into ground through soil and
underlying rock layer.
-Water cleaned as impurities filtered
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-Some water remains underground as groundwater.

-Some water returns to surface at springs or low
spots downhill.
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Groundwater Storage
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- water seeps downward underground into soil and
rock crevices
-then stored underground in rock crevices and in
the pores of geologic materials that make up the
Earth's crust
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-Water storage under the ground largely depends
on the types of soil and the types of rocks
present at the storage locations.
-underground storage occurs in the soil, in
aquifers, and in the crevices of rock formations
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Evaporation

• Conversion of water from a liquid into a gas
• Water transferred from surface to atmosphere
  through evaporation

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Evaporation the Sun

• The sun heats up water in the ocean, rivers, or
  lakes, turning it into vapor, which then goes
  into the air

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Evaporation Cont.

• 80 of evaporation from ocean
• 20 of evaporation from inland water and
  vegetation
• Winds transport evaporated water, influencing
  humidity around the world

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Transpiration

• The process of evaporation from plants.
  Basically, plants sweating.

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Transpiration Cont.

• Environmental factors that affect transpiration
• Light
• Temperature
• Humidity
• Wind
• Soil water

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Good For Plants!!

• Transpiration is the engine of plant life,
  pulling water up from the roots. This allows for
  photosynthesis, brings minerals from the roots to
  the rest of the plant, and cools the leaves.

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Water Storage in Atmosphere
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-atmosphere holds only very small percentage of
Earths water supply at any given time
-rapid recycling of water must occur between
earth's surface and atmosphere
World Water Supply
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- Water stored in the atmosphere can be moved
relatively quickly from one part of the planet to
another part of the planet
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