The Hydrological Cycle

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The Hydrological Cycle

• Martina Magee
• Thursday 16th June 2005

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CONTENT

• Concept of System and Cycles
• Water Balance
• Reservoirs
• Pathways
• Turnover Time
• Importance of Hydrological Cycle
• Impact humans have on the cycle
• Recycling of Earths Finite Resources

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HYDROLOGICAL CYCLEIntroduction

• The earth is a closed system.
• Cycling occurs from one compartment to another.
• Hydrological cycle is a biogeochemical cycle.
• Compartments are
• Biotic
• Abiotic
• Water Balance
• Precipitation (P) Evaporation (e) Runoff (D)
  Storage (S)

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Hydrological Cycle
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HYDROLOGICAL CYCLEReservoirs

• Reservoirs
• Ocean is the main reservoir
• Other reservoirs include Atmosphere Ice and
  Land based water bodies I.e. Rivers, Lakes,
  Ground Waters and Glaciers.
• Ocean accounts for 97 of Earths Water
• Freshwater reservoir accounts for lt 1 of
  Earths water.
• Humans use only 0.3 available water.
• Why use surface water?
• Rivers are accessible to us
• Easier to obtain water from a lake than from
  groundwater

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HYDROLOGICAL CYCLEPathways

• 2 main types of pathways
• Changes in Phase
• Precipitation
• Condensation
• Evaporation
• Transpiration
• Translocation
• Runoff and groundwater seepage
• Cycle is always in constant motion therefore,
  simultaneous action

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HYDROLOGICAL CYCLEChanges in Phase
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HYDROLOGICAL CYCLEChanges in Phase

• Evaporation the net transfer of molecules from
  the liquid to the gaseous phase.
• 80 occurs over Oceans and remainder over inland
  water and vegetation. WHY?
• Cause Solar radiation
• Transpiration Transfer of water from the leaves
  and stems of plants to the atmosphere.
• Vegetated Surfaces
• Evapotranspiration
• Combination of Evaporation and Transpiration
• Plants lie between 2 counterflowing movements of
  water transpiration and evaporation.

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HYDROLOGICAL CYCLEChanges in Phase

• Precipitation Primary mechanism of transporting
  water from the atmosphere to the surface of the
  Earth.
• Rain, Snow, Hail, Sleet and Freezing Rain and
  Dew.
• Causes of Precipitation
• Condensation (also a change in phase)
• Condensation Nuclei must be present Dew Point
• Volcanic Ash, Soil Dust, Smoke,Sea Salts,
  Particulate Matter - emitted by factories,
  vehicles.
• More precipitation falls over water than land.
  77 over ocean, remainder falling on land. Why?
  EVAPORATION
• Excess water returns to the oceans How?

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HYDROLOGICAL CYCLETranslocation

• Relates to both Run-off and Seepage.
• Runoff
• Movement of landwater to the oceans, mainly in
  the form of Rivers, Lakes and Streams.
• It is run-off that has neither evaporated,
  transpired or penetrated the surface to beome
  ground water.
• Classifications
• Direct/Base runoff relates to the speed of
  appearance after rain/snow
• Depending on the source it may be Surface Runoff,
  Storm Interflow or Ground Water Runoff

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HYDROLOGICAL CYCLEFactors which Affect Runoff

• Type of Precipitation
• Rainfall Intensity
• Rainfall Amount
• Rainfall Duration
• Distribution of Rainfall
• Meteorological Climatic Conditions

• Physical factors
• Land Use
• Vegetation
• Soil Type
• Drainage Area
• Elevation
• Slope
• Topography

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HYDROLOGICAL CYCLETypes of Flow

• Overland Flow Soil is either impermeable or
  saturated and the water flows on top of it.
• Underground Flow Slow movement of water through
  the ground.
• Groundwater Flow Sideways movement of water
  through the soil.
• Found in two soil layers
• Zone of Aeration
• Zone of Saturation
• Aquifers Water infiltrates downward through the
  soil and then flows laterally/sideways.

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HYDROLOGICAL CYCLEResidence Times

• Dependant on the reservoir the molecule is in
• Ocean 37,000 Years
• Glacier 16,000 Years
• Underground Water 300 to 4,600 Years
• Lake 1 to 100 Years
• River 12 to 20 Days
• Atmosphere 9 Days

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HYDROLOGICAL CYCLEWhy is it important?

• Sustain Human Life
• Agriculture

• Landscape
• Settlement

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HYDROLOGICAL CYCLEHuman Interaction

• Impact on Evaporation and Precipitation
• Cloud Seeding
• Dams
• Clearing of Vegetation
• Industry
• Impact upon Interception
• Vegetation Type
• Deforestation

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HYDROLOGICAL CYCLEHuman Interaction

• Impact of Urbanisation
• Settlement
• Industry
• Floods
• Attempts to control flooding
• Pollution
• Acid Rain
• Weathering

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RECYCLING

• Why Recycle?
• Finite Resources
• What are the resources used for?
• Fossil Fuels
• Used to make consumables
• Used to create other forms of energy

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RECYCLING

• Aluminium
• Extracted from Bauxite Ore, the process uses a
  lot of energy.
• Used in the packaging of many consumables,
  therefore is in high demand.
• Recycling saves 95 of the energy normally used
  to recover aluminium from ore.
• This decreases pressure on the resources and in
  turn the environment

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RECYCLINGOther Recyclable Resources

• Oil
• Improper disposal wastes resouce damages the
  environment
• Used oil can be refined and used for industrial
  lubricant fuel

• Water
• Has been recycled for billions of years
• Can be used for
• Irrigation, use in industry, Dual Plumbing
• Replenish groundwater supplies

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RECYCLINGBenefits

• Eases pressure on raw materials
• Saves Energy
• Reduction in Pollution
• Responsible Management

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SUMMARY

• Concept of System and Cycles
• Water Balance
• Reservoirs
• Pathways
• Turnover Time
• Importance of Hydrological Cycle
• Impact humans have on the cycle
• Recycling of Earths Finite Resources

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Thank You
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Flooding