3.1.1.2 water cycle W&C Flashcards
what are the 5 subsystems in the water cycle
hydrosphere, biosphere, cyrosphere, atmosphere and lithosphere
what is the lithosphere
outermost layer of the earth, includes the crust and the upper mantle
what is the hydrosphere
all the water on earth, may in liquid, gas or solid form
what is the atmosphere
the layer of gas between the earths surface and space, held in place by gravity
what is the biosphere
the part of the earths system where living things are found, all living things on earth
what is the cryosphere
includes all parts of the earths system where it is cold enough for water to freeze
what percentage of water is in oceans
96.9%
what percentage of water is in the cryosphere
1.9%
what percentage of water is terrestrial
1.1%
what percentage of water is in the atmosphere
0.001%
what percent of the earths surface is covered by oceans
72%
what is included in the cryosphere
sea ice (Artic ocean), ice shelves (Greenland and Iceland), ice sheets (land ice extending into the water), ice caps and permafrost (1-500m thick)
what is the residence time of cyrospheric water
15,000 years (longest)
what is included in terrestrial water
rivers, lakes, wetlands, ground water and soil water
why is atmospheric water vital
keeps the atmosphere at a temperature that maintains life
what is the residence time of atmospheric water
10 days
what are the three states of water
solid = ice
liquid = water
gas = water vapour
what is latent heat
when water changes state is needs heat or releases heat
what is evaporation
transfer of water from liquid state to gas
what is transpiration
water is lost from surface of vegetation when water vapour is realised through the stomata in leaves
what affects the rate of evaporation
amount of solar energy, humidity, temp of air, availability of water
what is condensation
air cools and holds less water vapour this means it will reach a point of saturation which is called dew point, excess water in the air will then be converted into liquid water
the water will need something to condense on this can be particles such as dust or smoke, or surfaces such as leaves, grass or windows that are below dew point temp
when do clouds form
when evaporated water condenses into a concentration nuclei
what conditions are needed for water to evaporate and rise
high temps, leads to high cloud coverage along the equator
what is precipitation
atmospheric water returning to the terrestrial system
what is the direct cause of all precipitation
condensation
what are the 3 types of rainfall
frontal, relief/orographic and conventional
what is orographic rainfall
when air is forced to rise over hills, cools and condenses and forms rainfall
what is frontal rainfall
warm air meets cold air, warm is less dense air rises and cools, condenses and forms rain
what is conventional rainfall
localised warm surfaces heat air above, this expands comes less dense and rises, forming rainfall
how many glacial and interglacial cycles have there been in the past 740,000 years
8 cycles
what happened in the last major glacial period
sea levels were approx 120m lower than present and continental glaciers covered much of Europe and North America, cause an interruption to the hydrological cycle
what is involved in an interglacial period
more melting than freezing which allows the hydrological cycle to perform as it does today, water can cycle between subsystems as it is not trapped in the cryosphere
what is runoff
atmospheric moisture that is transferred to the oceans on the surface or as groundwater
what is a key process determining how much water runs off
infiltration
when is surface runoff generated
when rainfall intensity is greater than infiltration capacity or when rain falls on soil that is already saturated
what is a drainage basin
the area which all water I’d drained by the same river and it’s tributaries
what factors affect flows in a drainage basin
vegetation density, soil porosity, slope gradient, precipitation intensity and water table depth,
what is watershed
an imaginary line which separates one drainage basin from another
what are human related factors that cause change at a local scale
deforestation, urbanisation and farmers digging drainage ditches
what is the water balance
shows the balance between the inputs and outputs
when does the water balance change
with the change of seasons
what is the water balance like in the winter
precipitation exceeds potential evaporation, leads to water surplus, soils will be saturated, overland flow encouraged and river levels will be high
what will the water balance be like in the summer
potential evapotranspiration will exceed precipitation, soil starts to dry out, at the end of the season there will be a deficit
what is a flood/storm hydrograph
how river discharge changes as a result of heavy rainfall
what is a river regime
the variability in the discharge throughout the course of a year in response to precipitation, temperature, evapotranspiration and drainage basin characteristics
what are the natural changes in the water cycle which cause variation
storm events, drought and seasonal changes
how do storm events cause variation
amounts and intensity of precipitation can affect amount of runoff, heavy storms cause higher discharge
how can drought cause variation
a reduction in water in rivers and lakes, vegetation dies which reduces transpiration, interception etc, soils dries out
what human activities cause change in the water cycle
farming practices, land use change and water abstraction
how do framing practices cause change in the water cycle
ploughing breaks topsoil which allows greater infiltration resulting in less runoff, irrigation adds extra water to the system, drainage systems lead to a more rapid transfer of water to the nearest river system and livestock may compact soil resulting in more runoff
how does land use change cause changes in the water cycle
urbanisation means more impermeable surfaces, water cannot infiltrate increasing overland flow and makes flooding more likely
deforestation is the removal of trees which leads to increased surface runoff and soil erosion, interception rates are reduced, recited infiltration due to less roots in soil
how does water abstraction cause change in the water cycle
the extraction of water from rivers or ground water aquifers, water stores are at danger of becoming depleted as rate of recharge is slower than rate of use
there is also a risk of contamination by inflowing sea water if the water table drops below sea level
