water cycle

• stores

  stocks of water/ places where the water is held

  Example - oceans
• Fluxes

  measurement of the rate of flow between stores
• Processes

  the physical factors which drive the fluxes of water between stores
• the hydrological cycle

  • evaporation
  • evapotranspiration
  • condensation
  • precipitation
  • surface run off
  • infiltration/ percolation
  • through flow
  • ground water flow
• Evaporation

  • the change in state from liquid to gas
• Evaportranspiration

  • the combined effects of evaporation and transpiration
• Condensation

  • the change from a gas to a liquid such as when water vapour changes into water droplets
• Precipitation

  • the movement of water in any form from the atmosphere to the ground
• Surface run-off

  • the movement of water that is unconfined by a channel acroos the surface of the ground
  • also known as overland flow
• Infiltration

  • the movement of water from the ground surface into the soil
• Percolation

  • the transfer of water from the surface or from the soil into the bedrock below
• Through-flow

  • water moving sideways through the soil, downslope under the influence of gravity
• Groundwater flow

  • the slow transfer of percolated water underground through previous or porous rock
• Closed system

  • where inputs and outputs are balanced
• Solar energy

  • energy from the sun heating water causing evaporation/transpiration
• Gravitational potential energy

  • ways in which water accelerates under gravity thus transporting it to rivers and eventually to the sea
• Residence times

  • are the average time a water molecule will spend in the resivoir or store
  • Antarctic ice residence times is over 800,000 years
• Cryosphere locks up 66% of the earths freshwater. As climate warms this is realised into the sea.

  polar regions contribute to global circulation of water and the transfer of heat which drive the thermohaline circulation
• Hydrological cycle

  • it is a closed system where no water is added to the global budget and none is removed
  • the system is driven from solar energy and gravitational potential energy
• drainage basin - area of land drained by a major river and its tributaries. they are open systems within the global hydrological cycle
• features of a drainage system


  • drainage basin- an area of land drained by a river and its tributaries
  • source - the start of the river
  • tributary - a small stream that joins a larger river
  • confluence - where a tributary joins a larger river
  • mouth - the end of a river usually where a river joins the sea
  • water shed - the edge of a river basin
• hydrological cycle is a system of linked processes

  • inputs - precipitation patterns and types of rainfall
  • flows - interception, infiltration, direct run off, saturated overland flow, through flow, percolation and groundwater flow
  • inputs - evaporation, transpiration, and channel flow
• drainage basin inputs


  • precipitation
  • convectional rainfall
  • orographic/ relief
  • frontal rainfall
• human impacts on drainage basins


  • over abstraction - when more water is taken from a source than being inputted
  • deforestation - the removal of forest and trees
  • changing land use - urbanisation - extracting water to meet the growing demand of a cities population
  • reservoirs - man made storage reservoirs interrupt the natural flows of water by delaying flows through a drainage basin and increasing the amount lost to evaporation
• physical impacts on drainage basins


  • climate
  • soil
  • geology
  • relief
  • vegetation
• • water budget - the difference between inputs of water and outputs of water in any given area
  • positive water balance - more than enough water
  • negative water balance - not enough water
• river regime - the annual variation in the discharge of a river there are two main types

  • simple regime - where the river experiences a period of high discharge followed by low discharge
  • complex regime - where larger rivers cross several different relief and climate zones and therefore experience the effects of different seasonal climatic events. human factors can also play a role in their complexity such as damming rivers
• factors that affect river regime


  • width of river
  • river characteristics
  • urbanisation
  • dredging
  • rates of evapotranspiration
  • irrigation
  • geology and overlying soils
  • wildlife
  • dams and reservoirs
  • vegetation type and percentage cover
  • climate variability (temp and precipitation)
• Rhone


  • peak flow - june/july
  • low flow - dec-mar
  • human factors- dams, locks
  • physical factors - shaped by neighbouring mountain systems
• Yukon


  • peak flow - spring and summer
  • low flow - winter
  • human factors - hydroelectric power use for mining
  • physical factors- conditions in Alaska is highly variable with temps going from one extreme to the next
• Murray- Darling

  • peak flow - wet season
  • low flow - dry season
  • human factors - water drawn for Australias major cities
  • physical factors - climate is seasonal sub-tropical
• Amazon


  • peak flow - wetter season
  • low flow- drier season
  • human factors - large dams used by Brazils major cities for irrigation
  • physical factors - the climate is tropical and has relatively consistent high temperature and rate of precipitation but there is some seasonal precipitation that leads to a low river discharge
• • storm hydrograph - shows variations in a rivers discharge at a specific point over a short period of time
  • the shape of a hydrograph changes because of physical and human factors and can be described as either 'flashy' or 'flat/subdued'
  • flashy hydrographs indicate there is a rapid increase in discharge and possibly a risk of flooding
• • peak rainfall - the highest amount of rainfall
  • peak discharge - the highest discharge
  • lag time - the time difference between peak rainfall and peak discharge
  • baseflow - the normal flow of the river due to groundwater seeping into the river channel
  • stormflow - resulting from increased precipitation involving both surface and throughflow
  • rising limb - shows how the flow of the river is rising
  • falling limb - shows the flow of the river decreasing
• sustainable drainage basins


  • tree pits
  • water buts/ water tanks
  • green roofs
  • rain gardens
  • ponds
  • wet land
  • permanent ponds
  • detention basins
  • permeable pavements
• draught - an extended period of deficient rainfall relative to the statistical multi-year average for a region
• types of drought


  • meteorological drought - occurs when long term precipitation trend is below the long term average
  • AGRICULTURAL DROUGHT - DEFICIENCY OF SOIL MOISTURE AND INSUFFICIENT WATER FOR CROPS SO THAT THEY WILL WILT WITHOUT IRRIGATION
  • hydrological drought - this happens the amount of surface and subsurface water is deficient due to lack of precipitation
  • socio-economic drought - this is when water demand exceeds supply. this has an impact on peoples ability to use water and their health
• EL nino- southern oscillation (ENSO) cycles


  • is a large mass of warm water in the equatorial pacific ocean.
  • the El Nino phenomenon occurs quasoperiodically (regular but not predictable