Water cycle theory Flashcards

1
Q

What is the ‘Goldilocks Zone’?

A

The zone in which Earth lies, which is the perfect distance form the Sun for water to appear everywhere on Earth in a liquid state

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2
Q

What % of the Earth’s surface is ocean?

A

71%

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3
Q

How does water moderate temperatures on Earth?

A
  • absorbing heat via oceans
  • clouds - reflect around 1/3 of solar radiation
  • water vapour (greenhouse gas) absorbs long-wave radiation from Earth helping to maintain temperatures by 15 dgrs C higher than they would be otherwise
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4
Q

What are the uses of water in flora?

A
  • photosynthesis - combining CO2, sunlight + water to make glucose + starches
  • respiration of plants = glucose to energy, releasing CO2 + water in process
  • plant cells require water to remain rigid (plant cells must be turgid to prevent wilting)
  • water transports mineral nutrients from soil to plant
  • transpiration for water from leaf surfaces cool plants by evaporation
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5
Q

What kind of system does water flow in at a global scale?

A

water flows in a closed system between the atmosphere, biosphere, oceans and land

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6
Q

What are the three main stores of water at a global scale?

A

atmosphere, oceans and land

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7
Q

what kind of system are smaller scale drainage basins?

A

at a smaller scale, eg drainage basin water cycle, these systems are open w inputs + outputs

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8
Q

What % of global water do oceans store?

A

97%

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9
Q

What % of global water does the atmosphere store and why is it such a small %?

A

0.001% - paradox can be explained by the rapid flux of water into + out of the atmosphere

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10
Q

What are the inputs of water to the atmosphere?

A

inputs of water to the atmosphere include water vapour evaporated from oceans, soils, lakes + rivers, + vapour transpired through leaves of plants. together known as evapotranspiration

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11
Q

how does moisture leave the atmosphere?

A

moisture leaves the atmosphere as precipitation + condensation

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12
Q

how do ice sheets, glaciers + snowfields release water?

A

ice sheets, glaciers + snowfields release water by ablation

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13
Q

how do precipitation + meltwater drain from the land surface and where does the water go?

A

precipitation + meltwater drain from land surface as surface runoff into rivers

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14
Q

a large part of water falling as precipitation on the land reaches rivers only after…

A

infiltrating + flowing through soil

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15
Q

what happens to water under gravity after infiltrating the soil

A

after infiltrating soil, water under gravity may percolate into permeable rocks or aquifers

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16
Q

what is an aquifer?

A

A layer of rock that is sufficiently porous to store water, and permeable enough to allow water to flow through it. for example, sandstone and limestone

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17
Q

what is groundwater?

A

Water stored within permeable rock underground, entering either through gaps between the grains (porous sandstone) or down joints and cracks in the rock (pervious limestone)

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18
Q

what happens to groundwater in the water cycle?

A

groundwater eventually reaches the surface as springs pr seepages + contributes to total surface runoff

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19
Q

what are the water flows?

A

precipitation, transpiration + condensation

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20
Q

how does precipitation occur?

A

forms when water vapour in the atmos. cools to dew point + condenses into water droplets or ice particles to form clouds. eventually, droplets/ice particles aggregate, reach a ‘critical size’ + leave the cloud as precipitation

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21
Q

what does aggregate mean?

A

a whole formed by combining several separate elements

22
Q

what is the dew point

A

the atmospheric temperature at which water droplets begin to condense + dew forms

23
Q

what is transpiration

A

the diffusion of water vapour to the atmosphere through leaf pores

24
Q

what % of moisture in the atmosphere is transpiration responsible for

A

transpiration is responsible for 10% of moisture in the atmosphere

25
Q

what is latent heat

A

the heat required to convert a solid into a liquid or vapour, or a liquid into a vapour, without change of temperature

26
Q

why is heat needed for evaporation

A

heat is needed for evaporation to occur in order to break the molecular bonds in liquid water. this is absorbed as latent heat - no temp change

27
Q

interception

A

when vegetation absorbs a proportion of precipitation, storing it temporarily on branches, leaves or stems. this moisture is evaporated (interception loss)

28
Q

what factors affect interception loss

A
  • interception storage capacity - as vegetation becomes saturated, stemflow + throughfall will increase
  • wind speed - evaporation rates increase w higher wind, leading to greater interception loss
  • vegetation type
  • tree species - evergreens have greater interception loss than deciduous as they have leaves all year round
29
Q

what is throughfall

A

rainwater that is briefly intercepted before dripping to the ground

30
Q

what is stemflow

A

the flow of intercepted rainwater to the ground along branches + stems

31
Q

what is percolation

A

slow movement of water through the pores in soil or permeable rock

32
Q

what is infiltration

A

the process by which water on the ground surface enters the soil

33
Q

what is overland flow

A

transfers water through the basin either as sheetwash, across the surface, or in tiny channels called rills

34
Q

what are the cryospheric processes

A

ablation - when glacial ice melts

meltwater - water released by the melting of snow or ice

35
Q

what is sublimation

A

process of changing directly from a solid to a gas

36
Q

how does urbanisation affect the water cycle

A
  • artificial surfaces (concrete) = impermeable, no infiltration can occur + no groundwater storage, meaning large surface runoff
  • also, urban development on floodplains reduce water storage capacity in drainage basins, increasing river flow + flood risk
37
Q

what human factors affect the water cycle

A
  • forest management
  • urbanisation
  • farming
38
Q

how does farming affect the water cycle

A
  • cropland intercepts significantly less precipitation, meaning less evaporation + transpiration form leaf surfaces
  • surface run-off increases where heavy machinery compacts soils. thus peak flows on streams draining farmland are generally higher than in natural ecosystems
39
Q

how does forestry affect the water cycle

A
  • high rates of rainfall interception in plantations of natural forestry
  • large proportion of intercepted rainfall is stored on leaf surfaces + is evaporated
  • compared to farmland, transpiration rates are increased
  • reduced run-off + stream discharge - high interception + evapotranspiration rates + absorption of water through roots, run-off is reduced
40
Q

what is clear felling

A

a forestry practise in which most or all trees in an area are uniformly cut down

41
Q

how does clear felling affect the local water cycle

A
  • clear felling increases surface run-off, reducing evapotranspiration + increasing stream discharge
  • however if clear felling is carried out sustainably, the changes to the water cycle should only be temporary as a proportionate biomass of forest will grow before next clear felling
42
Q

what has happened to the Artesian Aquifer in London

A
  • groundwater in the chalk aquifer is is trapped between two types of impermeable clay
  • rainwater enters the aquifer on the edge of the basin
  • groundwater flows through the chalk towards the centre of the basin
  • groundwater from the chalk is an important water for London
  • overexploitation in 19th + first half of 20th century caused a drastic fall in the water table
  • in recent years, the demand for water has fallen w the decline in industry + the water table has begun to rise to such an extent that in 1992, Thames Water has been abstracting water to prevent flooding
43
Q

what is a drainage basin

A

A river basin or drainage basin is an area of land drained by a river and its tributaries

44
Q

how has climate change affected the global water cycle?

A
  • global warming has increased evaporation, thus the amount of water vapour in atmos. has increased
  • water vapour is greenhouse gas, so more wv means further raising of global temperatures (positive feedback loop) as well as increased evaporation + precipitation
  • increased precipitation = higher runoff, raising flood risks
  • also accelerating melting of glaciers, ice sheets + permafrost, thus water storage in cryosphere shrinks as water is transferred to oceans + atmosphere - sea level rise
45
Q

what are the three reasons drainage basin planning might take place

A
  • to reduce runoff
  • to improve water storage
  • to maintain groundwater/aquifer levels
46
Q

rapid runoff, such as that caused by urbanisation and farming, is controlled by…

A

reforestation programmes in upland catchments, reducing artificial drainage + extending permeable surfaces in urban areas

47
Q

surface water storage is improved by…

A

conserving and restoring wetlands

48
Q

groundwater levels are maintained by…

A

limiting abstraction + by artificial recharge, where water is injected into aquifers

49
Q

how much water withdrawals and water consumption does agriculture account for globally?

A

agriculture is by far the biggest consumer of water, accounting for 70% of water withdrawals + 90% of water consumption

50
Q

what is waterlogging?

A

land saturated with water