Hydrosphere

• Water storage

  Oceans: 97%

  Ice and snow: 2%

  Lakes and rivers: 0.02%

  Soil: 0.005%

  Atmosphere: 0.001%

  Biosphere: 0.0001%
• Hydrological cycle


  The continuous circulation of water between the Earth's oceans, atmosphere, and land
• The change of water from liquid to gas is called evaporation
• The change of water from gas to liquid is called condensation
• Evaporation


  The change of water from liquid to gas as hydrogen bonds are broken
• Transpiration

  The loss of water from plants by the evaporation of water in the stomata in leaves
• Interception


  Precipitation that does not reach the ground because it lands on vegetation
• Infiltration


  The process by which surface water enters the ground between the particles of soil or rock
• Percolation


  The movement of water between the particles of soil or rock
• Groundwater flow


  The movement of water through the pore spaces and fissures in permeable rocks
• Runoff


  Water flowing over the surface of the Earth, where the infiltration capacity of the ground has been exceeded
• Human activities change dynamic equilibrium by altering: rates of processes, residence times and quantities in hydrological cycle reservoirs
• How does deforestation alter the hydrological cycle?

  • reduced interception
  • Reduced transpiration
• How does urbanisation alter the hydrological cycle?

  • Increased runoff
  • More rapid runoff
  • Increased flood risk due to increased river flow
• How does drainage affect the hydrological cycle?

  • Field drainage reduces soil moisture and increases river flow
• How does soil compaction affect the hydrological cycle?

  Reduces infiltration and increased runoff
• How does human created climate change affect the hydrological cycle?

  • Faster evaporation
  • More sudden/heavier precipitation
  • Melting of snow and ice
  • Delayed condensation and precipitation
  • Altered wind strength and direction - alters precipitation
• How does water abstraction from rivers affect the hydrological cycle?

  • reduced downstream flow in rivers
• How does water abstraction through reservoirs affect the hydrological cycle?

  • altered downstream flow
  • reduced turbidity downstream
  • sedimentation in reservoir
• How does water abstraction through aquifers affect the water cycle?

  • loss of surface water features
  • saltwater incursions into costal aquifers
• Consequences of changes in the hydrological cycle:

  • Flooding - due to heavy rainfall and more rapid urban drainage
  • Drought - caused by reduced precipitation following deforestation
  • River flow fluctuations - caused by all of the above and reservoir flow regulations
• Unsustainably exploited water sources:

  • Rivers: Colorado river, yellow river (China) and Murray darling river (Australia)
  • Aquifers: High plains aquifer and north china plain aquifer
• Sedimentation

  The water is allowed to remain static to let suspended solids such as silt settle
• Screens

  Metal grills or meshes are used to remove vegetation and litter such as plastic and paper items from the fluid flow
• Aeration

  Bubbles of air or water sprays are used to aerate the water and ensure a high dissolved oxygen content. Water sources that are anaerobic may contain hydrogen sulfide from the decay of organic matter, which makes the water smell of bad eggs. Some dissolved metals that are toxic or give the water a bad taste are removed by aeration as they become insoluble
• Flocculation/coagulation and clarification

  Clay particles are neutralised by adding flocculants such as aluminium sulfate (alum) or polyelectrolytes. They are mixed quickly with the water then passed into the clarifier tank where the particles are allowed to settle
• Filtration

  In some treatment plants, filters are used to remove any remaining suspended solids and bacteria. These often involve slow flow through layers of sand and gravel
• Activated carbon filters

  Particles of activated carbon are used to remove organic chemicals such as pesticides by adsorbing onto the carbon particles
• Sterilisation

  The addition of chlorine, ozone, or exposure to ultraviolet light is used to sterilise the water and pathogens. Chlorine is the most common method but if the water is from peaty sources then organic matter may be present which could react with the chlorine and produce toxic substances. In this case, UV light is used. Using chloramine keeps the water sterile for longer as it breaks down gradually and releases chlorine. pH control is necessary as sterilisation with chlorine can make the water too acidic, adjusted by adding crushed lime
• Fluoridation

  Fluorides are added to water in some areas to improve dental health
• Ion exchange

  Toxic ions such as lead, mercury, and arsenic can be removed from water using ion exchange resins. The toxic ions adsorb onto polymer beads or particles of zeolite. Ion exchange is also used to remove calcium and magnesium ions to produce soft water
• Reverse osmosis

  Seawater is filtered at very high pressure through partially permeable membranes to remove salt. The fresh water collected has about half the original volume, and the remaining salty water is returned to the sea. Desalination is expensive and only carried out if other water sources are unavailable due to the high energy needed to produce the very high pressures
• Distillation

  Water is boiled by heating and/or reducing the pressure. The steam produced is condensed and collected
• What is metering?

  Payment per volume used - encourages lower use
• What are examples of lower water use appliances?

  • Dual flush toilets
  • Aerated spray taps
  • Drip feed irrigation
  • eco friendly washing machines (reuse water)
• What is grey water use?

  Reusing wastewater from sources like sinks and showers for purposes like irrigation.
• How can water storage be used for more sustainable water use?

  • River regulation reservoirs
  • Aquifer recharge
• why is catchment afforestation important ?

  • Reduces runoff fluctuations - more regular inflow into reservoir
• How to reduce water wastage?

  • better maintenance of pipes and appliances
• Exploitation of new sources:

  • Rainwater catchment
  • new reservoirs - consider all ideal site conditions
  • Estuary barrages - to collect and store river water often close to ur an areas but high pollution risk
  • Unexploited aquifers - with suitable geology
  • Inter basin transfers - move water between a river catchment that has a surplus to one with a shortage