3.1.1.2 The Water Cycle Flashcards
What are the five main sub-systems?
Lithosphere Hydrosphere Cryosphere Atmosphere Biosphere
What percentage of global water is stored in oceans?
96.6%
How much of the Earth’s water is fresh water?
3.7%
Of the total amount of fresh water on Earth, what percentage is stored as snow and ice?
69%
Of the total amount of fresh water on Earth, what percentage is groundwater?
30%
Of all fresh water on earth, how much is surface or atmospheric water?
1.2%
What are the five main oceanic stores?
Atlantic, Pacific, Indian, Arctic and Souther
What are the five main stores of cryospheric water?
Sea Ice - Antarctica Ice Caps - Icelandic cap Ice sheets - Greenland Alpine Glaciers - Mer de Glace , France Permafrost - Alaska
How much would sea levels rise by if the Greenland ice sheet melted?
6m
If the Antarctic ice sheet melted, how much would sea levels rise?
60m
What are the main stores of terrestrial water?
Surface
Ground
Soil
Biological/biomass
What are the main processes in the water cycle?
Evaporation, condensation, transpiration, cloud formation, precipitation formation
What are the main processes in the cryosphere?
Accumulation - snow building up
Ablation - melting
How long does water typical remain in rivers?
2-6 months
How long does water typical remain in soil?
1-2 months
How long does water typical remain in ground water?
100-100,000 years
How were water stores different to 18,000 years ago - last ice age?
Thicker/Larger ice sheets and glaciers
Higher extent of permafrost
There would be much less liquid water so oceans would be about 100m lower
Atmospheric water levels would reduce as low temps don’t encourage evaporation
Low temperatures limit plant growth, so smaller stores in the biosphere
Outline global precipitation
precipitation is high around the equator/between the tropics in the low pressure zones
high at mid latitudes
what is low pressure?
rising warm air, moist air cools and condenses to form huge clouds and heavy rain
where is precipitation very low?
at around 30 degrees N and S
Why is precipitation high at mid latitudes?
due to the convergence of warm air from the tropics and cold air from the Arctic creates an active polar front.
Moist tropical air from the south is forced to rise over denser cooler air from the north resulting condensation, cloud formation and rain
what are the main processes in the drainage basin
precipitation, evapotranspiration, surface run off, infiltration, throughflow, stemflow, percolation, ground water flow
what are the main stores in a drainage basin?
from shortest to longest : interception, soil moisture, river channel, surface storage, ground water
what happens to the stores in a drainage basin during winter?
temperatures are lower so there is less plant growth
evapotranspiration is lower infiltration and soil storage will increase until saturation is reached
increase in run off and the risk of flooding
what happens to the stores in a drainage basin during summer?
higher temperatures mean greater evapotranspiration so less water is stored on the surface or is available for infiltration
greater vegetation cover increases infiltration and transpiration so less water reaches ground water stores.
river levels are likely to fall
what is river discharge and how is it calculated?
the volume of water passing a given point in a given time expressed in cumecs
channel cross section area x velocity
what is a river’s regime?
the typical rises and falls in river discharge over the course of a year
for a typical river in the UK, when would river discharge occur during a year and why?
the winter months have greater precipitation than evapotranspiration so soil water stores fill up
for a typical river in the UK, when would soil moisture utilisation occur during a year and why?
spring months as temperatures rise and evapotranspiration exceeds precipitation and the water store is used by plants
or a typical river in the UK, when would a soil moisture deficit occur during a year and why?
summer months as all soil moisture is used up and any precipitation will now go into the soil rather than a river so river levels fall
or a typical river in the UK, when would soil moisture surplus occur during a year and why?
end of winter/early spring as precipitation is greater than evapotranspiration and the soil has already been recharged so their is a surplus
flooding can occur when the soil is saturated
what is a storm hydrograph and why are they important?
a graph of the discharge of a river following a rainstorm event
they are important because they can predict how a river might respond to a rainstorm which can help in river and flood management
what terms label a storm hydrograph?
rising limb, falling limb, peak discharge, lag time, baseflow, peak rainfall
what physical factors could lead to a river having a short lag time?
small, circular drainage basin steep relief of slopes antecedent rainfall impermeable soil or rock limited vegetation intense or prolonged rainfall
what human factors could lead to a river having a short lag time?
deforestation, farming practices, urbanisation
what are some effects of a long period of drought on the water cycle?
initially high rates of evapotranspiration until surface stores dry up
vegetation destroyed by wildfire which removes all processes trees are accountable for
groundwater transfer will continue to feed rivers until the water table drops too far causing some rivers to dry up
what are some effects of a severe storm on the water cycle?
intense rainfall will exceed infiltration capacity of the soil leading to flash flooding
limited amounts of water will reach groundwater stores
why will land use change of urbanisation and deforestation cause change in the water cycle?
catchment areas that are no longer natural are less likely to have permeable surfaces for precipitation to infiltrate to.
increased risk of flooding and flash flooding
soil erosion will occur at a quicker rate due to the removal of trees
why will agricultural change cause change in the water cycle?
some farming practices result in excess drainage of the ground
livestock can compress soil which reduces soil storage capacity
soil is left vulnerable to erosion after ploughing and harvesting of crops
why will water abstraction cause change in the water cycle?
if water is removed faster from aquifers than it is replenished, then the water table will fall and ground stores will reduce over time. this can lead to falling river levels and the intrusion of salt water from the sea in areas near to the coast
