The Hydrologic Cycle

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The Hydrologic Cycle
Rita Haberlin
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What You Learn

• The role of water in the global ecosystem
• The properties of water including latent heat
• Where the worlds water supply is stored
• The pathways of moisture in the hydrologic cycle
• The fate of precipitation on the land
• How ground water moves in rocks beneath the
  earths surface
• Mans impact on ground water depletion and
  pollution

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What kind of Mass Wasting?
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Introduction

• Earth is called the blue planet. Why?
• 70 of the earths surface is oceans -
  hydrosphere.
• The hydrosphere connects with the three other
  spheres

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The Worlds Water Supply
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Water Takes Three Different Forms

• Liquid
• Solid
• Gas

• Water
• Ice
• Water vapor

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The Properties of Water - Latent Heat

• Water is a fidgety substance
• It constantly shifts between three states solid,
  liquid, and gaseous
• Every time water changes form, heat is either
  released or absorbed

Ice
() heat is absorbed
(-) heat is released
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The Hydrologic Cycle
What is the driving force for the hydrologic
cycle?
Atmosphere

• Solar Energy
• Gravity keeps it moving between
• hydrosphere
• biosphere
• lithosphere
• atmosphere.

Lithosphere
Hydrosphere
Biosphere
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Pathways of Moisture in the Hydrologic Cycle
All the worlds water comes from the oceans. In
the end, most of it returns to the ocean. HOW?
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The Fate of Precipitation on Land
Precipitation is the source of water for the
continents
Transpiration
(Evapotranspiration)
Precipitation
Evaporation
Infiltration
Percolation
SOIL WATER BELT
GROUND WATER
Groundwater Runoff
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Distribution of Ground Water

• Zone of aeration
• area above the water table mostly filled with air
• Water table
• top of the zone of saturation
• Zone of saturation
• All the pores and cracks filled with water

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How can water move underground?

• Movement depends upon
• Porosity
• Percentage of pore space available to hold water
• Permeability
• Ability to transmit water through connected pore
  spaces

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Porosity

• Some rocks have pore spaces but they do not allow
  water to pass through
• Clay and shale
• Some rocks do not have pores - they consist of
  intergrown crystals

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Permeability

• Rocks that allow water to pass through them are
  called permeable
• Rocks that do not allow water to pass through are
  called impermeable

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Aquifers

• The best aquifers (groundwater storage areas) are
  both
• porous
• permeable
• Sandstone is a good aquifer rock

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water table
impermeable
Aquiclude
permeable
Aquifer
impermeable
Aquiclude
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Animated Artesian Aquifer
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Springs
Clay layer
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Water Tables Rise and Fall
The water table is the top of the zone of
saturation
After a period of rains
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Water table
After a long drought
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Ground Water Depletion
If ground water is removed faster than it is
naturally recharged, the water table lowers.
Over pumped well
Dry well
Cone of depression
Natural water table
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Overpumped wells
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What is the Impact of Widespread Pumping?

• Shallow wells dry up
• Rivers and lakes dry up between rains
• Land subsidence
• Salt water intrusion

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Subsidence World-Wide
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Subsidence in the Central Valley
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Salt Water Intrusion

• Water table near the coast lowers
• Salt water seeps into the aquifer
• Coastal wells draw brackish water

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Sources of Ground Water Pollution
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Toxic Waste Sites
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Human Impact

• Which well will have the cleanest water?
• Why is well D likely to be polluted?
• Will heavy pumping of well A affect other wells?