3.1.1.2 the water cycle

• Hydrosphere - Any liquid water

  Lithosphere - Water stored in the crust and upper mantle

  Cryosphere - Any water that is frozen

  Atmosphere - Water vapour
• • Shallow groundwater aquifers can store water for up to 200 years, but deeper fossil aquifers, formed during wetter climatic periods, may last for 10,000 years.
• glaciers may store water for 20-100 years, which may feed lakes that store water for 50-100 years.
• Farming Practices:

  Ploughing breaks up the surface, increasing infiltration

  Arable farming (crops) can increase interception and evapotranspiration

  Pastoral (animal) farming compacts soil, reducing infiltration and increasing runoff
• Land Use Change:

  Deforestation (e.g. for farming) reduces interception, evapotranspiration and but infiltration increases (dead plant material in forests usually prevents infiltration)

  Construction reduces infiltration and evapotranspiration, but increases runoff
• Water Abstraction (water removed from stores for human use):

  This reduces the volume of water in surface stores (e.g. lakes).

  Water abstraction increases in dry seasons (e.g. water is needed for irrigation)

  Human abstraction from aquifers as an output to meet water demands is often greater than inputs to the aquifer, leading to a decline in global long-term water stores
• convectional rainfall

  • south + southerneastern UK in summer
  • intense solar insolation heats up ground > RCCC
• orographic rainfall

  • moist warm air form westerlies/atlantic hits high relied of lake district/pennines = RCCCR = rain on windward side + rainshadow effect on leeward side
• frontal rainfall

  • warm air = less dense than cold air
  • forced over cool air = rcccr
  • low pressure system
  • most of uks rainfall
• drainage basin = local open systems
• throughflow - downhill through soil
• percolation - water > watertable via porous rocks
• ground water flow - H2O below water table = slow
• baseflow - ground water to river
• interflow - H2O above water table, water flows into river
• channel flow - river discharge
• natrual variation to water cycle storm events + seasonal changes

  Seasonal Changes:

  • Less precipitation, more evaporation in summer because of higher temp
  • Reduced flows in winter as water is stored as ice + less interception in winter, when deciduous trees lose their leaves
  • Increased evapotransp in summer; deciduous trees have their leaves/higher temperatures
• storm hydograph

  • river discharge over time in cumecs. m3/s during/after storm event
  • peak discharge - highest point = river d greatest
  • lag time - delay between peak precip + peak disch > water takes time to flow in the river
  • rising + falling limb = increases as h2o flows into river + reduces as less h2o flows in
• why do we use storm hydrographs

  • provides info for planners +managers on circumstance of flood in particular areas
  • assess likelihood of floods
  • see if management schemes are working by comparison of previous flood hydrographs
  • assess impacts of flood use
• hydrosphere

  • 1.4 sextillion tonnes
  • 97% saline
  • 3% fresh water
• fresh water - 3%

  • 69% cryosphere
  • 30% groundwater = lithospshere
  • 0.3% lakes + rivers =
  • 0.04% water vapour in atm