droughts are long periods of time with below average precipitation
meteorological causes
short term precipitation deficits
ENSO cylcles
anticyclones (air does not rise so condensation and cloud formation does not occur)
changes to ITCZ (inter tropical convergence zone)
el nino - reverse of the Walker's cells - high pressure accumulates above australia - causes drought like conditions, S America - low pressure so flooding and intense rainfall
la nina - intensification of walker loop - australia has low pressure and S america has high pressure
Murray Darling Basin - 2006 Australian drought
human activity - adds to drought risks due to over-abstraction of surface water resources and ground water aquifers
deforestation reduces the soils ability to store water - causes land to dry out
construction of dams - restricts water downstream
drought has impact on ecosystem functioning as wetlands
drought can cause loss of wetlands and forest stress - highlighting resilience of ecosytems
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Surpluses within the hydrological cycle
surpluses within the hydrological can lead to flooding
meterological causes of flooding
instense storms
heavy and prolonged rainfall
depressions (low pressure)
extreme monsoonal rainfall
snowmelt
humans exacerbate flooding
urbanisation and deforestation
increase in impermeable surfaces - surface run off
deforestation reduces the amount of water intercepted - increase in surface runoff
changing land use
mismanagement of rivers and inadequate hard engineering
damages economic activity
ruins infrastructure and settlements
environmental impacts - damage the ecosystems
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The role of climate change on the hydrological cyc
climate change effects the inputs and outputs of the hydrological cycle - altering the precipitation and evaporation rates
climate change impacts on:
stores
flows
size of snow and glacier mass
reservoir
lakes
permafrost
soil moisture levels
run off rates
climate change impacts are uncertain
concern over water supplies and efficency of management
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