3.1.1.2 The Water Cycle Flashcards
what are the processes of change (pt 1)?
- groundwater flow (transfer of water through rocks, often below water table after percolation + infiltration
- percolation (water soaking into rocks)
- river flow (water flowing through river)
- infiltration- water enters openings in ground from surface
- sublimation- water from solid to gas
- precipitation- transfer of water from atmosphere to earth’s surface as rain, snow, hail etc
- condensation- conversion water from gas to liquid (clouds)
what are the processes of change (pt 2)?
- interception- water intercepted + stored on leaves of plants
- evapotranspiration- combination of evaporation (liquid to gas due to temp/pressure) + transpiration (moisture carried through plant where it turns to vapour + enters atmosphere)
- overland flow- flow over lands surface
- through flow- water flowing through soil to river channel
- convectional rainfall- land warms= heats air above it= air expands + rises= as rises it cools + condenses= process continues= rain will fall
- trunk + stem flow- flow of water down plant/tree trunks
hydrospheric processes- temporal change
- short-term= runoff, precip + evap
- oceans supply 90% water in water cycle
- THC= influences short term changes in climate especially rainfall in places
hydrospheric processes- spatial change
- since last glaciation= sea levels risen by 120m
- cold glacial periods= lower sea levels as more water locked in cryosphere on land
- where processes are occurring= changing climate across world in diff places
lithospheric processes- temporal change
- store captures water for longest period of time
- water from lithosphere to underground aquifers (slow transfer)
- water stored in rock pores for hundreds of years
lithospheric processes- spatial change
- rivers, lakes= surface freshwater stores
- lake Baikhal (Russia)= 20% of planets surface freshwater
- water stores underground in aquifers
- water exists on crust as terrestrial water- rivers, lakes, aquifers etc
biological processes- temporal change
- evapotranspiration from plants= more water vapour in atmosphere= more condensation
–> this stops as much insolation from sun getting to earth surface= affects water cycle + waters stored in plants
biological processes- spatial change
- plants pump water to air= increase humidity= forms clouds + rain
- less plants= increases arid (dry) climates
atmospheric processes- temporal change
- storms + winds transfer water across planets surface
- little storage, lots of movement
atmospheric processes- spatial change
- water not evenly spread e.g. warm air holds more moisture + air above equator
cryospheric processes- temporal change
- ice= more in summer/’interglacial’ periods
- ice age= lower sea levels as more water locked on land surface as ice
- short-term changes in snowfall
- albedo effect, less sea ice= more evap= less albedo overtime= more warming + absorption
- permafrost stores ice in cold periods but melts in warm
cryospheric processes- spatial change
- 1/3 of earths land is ice sheets (90% of Antarctica)
- ice age= sea levels fell by 100m
60m sea level rise if all ice sheets melt - regions with more precip= more ice
- less albedo + warming in areas with ice
- permafrost is found in polar, high mountain regions
evaporation rates over time + space
over time:
- day- lots of solar radiation= tropics lots of evap
- year- seasonal , hotter months= more evap
- 100 years- climate change, land use change, farming, changes in law can influence it
space:
- near equator= more evap
- poles= less evap
- tropics= high temps, sunlight, frequent rain= high evap
condensation rates
- summer + spring= warmer air can hold moisture so more condensation
- as air rises (over a mountain)= it cools= condensation –> this will stop when air becomes saturated
rainfall rates
over time:
- day= enough moisture= more precip
- year- seasons= changes in rainfall
- 100 years- climate change influences long-term
global distribution of water stores
earths FRESH water:
groundwater (stored in permeable rock in lithosphere) –>30%
surface water (lakes, rivers, etc) –> 0.3%
cryosphere–> 69%
water vapour in atmosphere–> 0.04%
how long does water remain in the different water cycle stores?
- groundwater (deep)= 10,000 years
- groundwater (shallow)= 20-100 years
- glaciers= 100-200 years
- lakes= 50-100 years
- seasonal snow cover= 6 months
freshwater info
- freshwater= only 2.5% of earths water
- only 0.9% of it is accessible to humans
global atmospheric circulation model
see mind map
types of rainfall?
frontal
convectional
relief
frontal rainfall
- area of warm air meets area of cold air
–> warm air is forced over cold air
–> where air meets= warm air’s cooled + water vapour condenses= clouds form
convectional rainfall
- sun heats ground + warm air rises
–> it rises, cools + condenses= clouds form
–> large clouds can form= heavy rain storms
relief rainfall
- warm wet air rises over high land
–> it rises, cools + condenses= clouds form + precip occurs
–> dry air then descends + warms + any moisture in air evaporates
cloud formation
- vapour molecules slow down due to cooling air
–> the can’t maintain vapour form so condense to tiny liquid droplets
–> tiny droplets form + combine to make a cloud –> often clusters of a particle e.g. dust
–> condensation nuclei
water balance + water balance formula
- balance of inputs + outputs (helps us to know how much water is stored in the system + drainage basin behaviour)
- summer (dry seasons)- evapotrans. exceeds precip= negative water balance
- more precip than evapotrans= positive water balance
formula:
P= Q + E +/- S
(precipitation= runoff + evapotrans. +/- change in store
what is discharge
discharge= volume of water flowing through a river in a given time
residence time meaning
period of time water spends in a store
river regime meaning
rivers discharge changes throughout the year
storm hydrograph human influences
urbanisation, agriculture, deforestation, river management, drainage system
storm hydrograph physical influences
excessive/prolonged rainfall, saturated soil, snow melt, frozen soil, impermeable rock, high drainage density, steep gradient, depth of river bed
components of a storm hydrograph
rising limb, peak rainfall, peak discharge, lag time, falling limb, base flow
y- axis= precipitation (mm)
x-axis= time
flash hydrograph vs flat hydrograph
flashy- short lag time + high peak discharge, rising limb steep
flat- low peak discharge, gradual rising + falling limb
evaporation- what does it depend on + spatial + temporal points
- depends on energy from solar radiation, availability of water, humidity, temp of air
–> more evap in warm areas, less windy, less humid, faster evap in area of large surface area, higher altitude= lower atmosphere pressure= more evap
–> more evap in summer, in day, short-term changes in weather patterns, long-term due to climate change, EL Nino/La Nina etc
transpiration what is it affected by
wind speed, temp, humidity etc
condensation when does it occur
occurs when there’s excess water in air:
- when temp of air is reduced to dew point but volume remains constant
- when volume of air increases + there’s no addition of heat –> can occur when air forced over hills as it will expand at lower pressures etc
precipitation what is it affected by (spatial + temporal)?
spatial:
- geography + topography- mountains can block moist air= less rain on one side. Coastal areas often have more rain
- latitude- near equator= more precip due to ITCZ where warm air rises + cools
- vegetation- forests= higher humidity + precip due to transpiration
- proximity to water bodies- nearer oceans= more evap= more humidity + precip
temporal:
- seasonal changes (wet +dry) due to shifting positions of ITCZ
- climate patterns- El Nino (brings wetter conditions to southern US + drier to Australia) + La Nina
- weather systems- storms etc
- climate change- long term precip changes (more intense, frequent etc)
what is the soil water budget
describes the changes of the soil water budget during the course of the year
explain the soil water budget
- see mindmap
humans factors (HF) affecting changes in the water cycle?
farming practices
land use change
deforestation
water abstraction
(HF) farming practices - what does arable + pastoral farming + ploughing do
ploughing= breaks surface= increases infiltration
arable (crops)= increase interception + evapotrans
pastoral (animal)= compacts soil due to trampling= less infiltration + more run off
(HF) farming practices - irrigation
wells= main source of irrigation in plants= lowers groundwater levels + river channel levels
- irrigation= increase run off as not all water can infiltrate
- irrigation= higher in summer
(HF) farming practices - impacts of farming in arid regions
can lead to desertification= soil will have less capacity to store water
(HF) farming practices - fertilisers + farming machinery + overgrazing + more crops
impacts
fertilisers can lead to eutrophication
farming machinery compacts soil= increase runoff
overgrazing= less crops= less interception etc
more crops= more infiltration + interception + evapotranspiration= maybe more rainfall in area etc
(HF) farming practices - Jordan valley (Israel) + low lying land
Jordan valley (Israel)- net bananas to reduce evap
low lying land e.g. somerset- once submerged but dug network of ditches to move water quickly through system= creates farmland BUT downstream flooding in York
(HF)- land use changes
- people living in urban area increasing= construction of roads, buildings etc= more impermeable surfaces= less infiltration + more runoff
- city drainage systems remove water quickly BUT can cause flooding if river channels can’t discharge excess run off quickly
- urbanisation= replacing vegetated ground with impermeable surfaces (concrete etc) –> reduces soil water + groundwater stores
(HF)- deforestation
- vegetation removal for agriculture, urbanisation or firewood for fuel= soil moisture reduced= transpiration declines= less precip
locally dry rivers, desertification etc
BUT
dead plant material on forest floor can hold water= slows infiltration= won’t just runoff - old vegetation has larger root systems that can hold more water + more leaves that will intercept
HF water abstraction- why is it increasing + impacts of excessive abstraction from aquifers
- growing population, irrigation (mainly in summer/dry seasons), drinking water etc= demand for water supplies increase= reduces water on surface stores
- excessive removal of aquifer water= recharge can’t keep up + stores deplete
–> this can allow seawater in if water table drops below sea water/salinisation if water table rises + evap leaves natural salt conc behind
HF water abstraction- middle east + abstraction licences
middle east= water abstracted from underground aquifers that were formed years ago= they’re in severe danger of becoming depleted as rate of recharge= slower than rate of use
- abstraction licenses= being changed
HF water abstraction- what is sea water intrusion
- when groundwater is withdrawn at faster rate than it can be replenished by rainfall= seawater moves into the freshwater aquifers –> groundwater levels too low= they get contaminated with sea water= irreversible water isn’t drinkable/harms crops etc
deforestation- spatial + temporal changes
spatial:
- more likely in poor nations for firewood etc
- urbanisation etc
temporal:
- greatest loss of evapotrans= felt in summer
agriculture- spatial + temporal
spatial- more prominent in LIC’s
temporal- lowering water table= most likely in summer + live stock more likely to roam in summer
abstraction- spatial + temporal
spatial- occur in areas with porous geology
more common in wealthy nations with tech to abstract
high demand in tourist locations
temporal- more likely to occur in summer when surface water= less available
physical factors/variations affecting water cycle- storms + precip
- extreme weather events e.g. severe storms/droughts= significantly impact water cycle
- storms + precip- intense storms= more precip= higher peak discharge than light rain
–> larger input of water= flows increase in size
–> some flows e.g. infiltration can’t occur rapidly= runoff + overland flow
physical factors/variations affecting water cycle- seasonal changes + natural climate change
- variation of inputs, flows + stores with seasons
winter= more precip, snow delays water availability until melted, lower temps= less evap, saturated soils= more overland flow, vegetation dies= less interception + transpiration, higher discharge rates, frozen water
summer= less precip, higher temps= more evap, soil may dry out= less rain infiltrates quick BUT hard, baked soil= impermeable, more veg= more evapotrans= less infiltration= increase lag time, lower discharge rates
natural climate change–> impact of ice ages, interglacial (period of warming) + glacial periods etc
what occurs in a normal year vs el nino?
normal year
- trade winds blow consistently east to west over pacific ocean –> pushes warm water west towards Australia, Philippines etc + cold water from underneath replaces the east water (cold upwelling). due to warm water= low pressure system forms with rising air= creates cycle of warm air falling + dry air falling
El Nino year
- trade winds weaken= warm water not pushed west + stays over most the pacific ocean= less suspending= dry airs falling both east + west= effects whole world
el nino impacts
- S. Africa= droughts, E. Africa= floods
- cold, dry winters in Europe
- western Austrailia had bush fires
- typhoons in china
- argentina= wetter weather
- warmer summers in Belgium + Holland
what is la nina + impacts of it?
- opposite to El Nino where trade winds strengthen= greater upwelling of cold water across Pacific Ocean= opposite affects of El Nino
impacts:
- rainfall increase in Phillipines + austrailia
- E. Africa= have droughts
