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A Level Environmental Science > The Hydrosphere > Flashcards

The Hydrosphere Flashcards

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1
Q

What are the 7 reservoirs of water in the water cycle?

A

Oceans
Land ice
Groundwater
Atmosphere
Living organisms
Lakes and rivers
Soil moisture

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2
Q

What is residence time (RT)?

A

The average amount of time that a water molecule is present in a reservoir of water

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3
Q

What is transfer rate?

A

The volume of water that is transferred over a period of time (e.g. litres per second)

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4
Q

What is the calculation for residence time?

A

RT = Volume of water in a reservoir / Mean transfer rate

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5
Q

What is the estimated volume of water in Earth’s hydrosphere?

A

1,500,000,000 km3

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6
Q

Which reservoir has the longest RT?

A

Groundwater (5000 years)

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7
Q

Which reservoir has the shortest RT?

A

Living organisms (7 days)

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8
Q

Which reservoir contains the largest volume of water?

A

Oceans (97% of water on Earth)

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9
Q

Which reservoir contains the smallest volume of water?

A

Living organisms (0.00004%)

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10
Q

Where does the energy that drives the water cycle come from?

A

The Sun

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11
Q

What is abstraction?

A

Taking water from a natural reservoir for human use

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12
Q

What are some examples of human activities which affect the water cycle?

A

Urbanisation, agriculture, deforestation, afforestation, global climate change

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13
Q

What are the effects of agriculture on the water cycle?

A
  • Abstraction for irrigation can cause aquifer depletion (over-drafting)
  • Heavy machinery or livestock trampling can cause soil compaction which would increase surface runoff
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14
Q

What is the link between interception and infiltration?

A

Water is more likely to infiltrate when slowed down by interception

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15
Q

What are the 4 factors which cause a change in the demand for water?

A

Change in population
Change in affluence
Change in industry
Change in agriculture

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16
Q

How does population affect demand for water?

A

Increased population leads to increased demand

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17
Q

How does affluence affect demand for water?

A

Increased affluence (wealth) leads to increased demand due to more money and appliances

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18
Q

How does industry affect demand for water?

A

Heavy industry (such as paper production) requires more water than the service industry

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19
Q

How does agriculture affect demand for water?

A

Intensive agriculture requires more water than small-scale or subsistence agriculture

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20
Q

What are the consequences of human impacts on the water cycle?

A
  • Dynamic equilibria in the hydrological cycle are negatively affected as transfer rates are changed
  • Reservoirs of water may become depleted and be unable to recover immediately
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21
Q

What is per capita water use?

A

The mean water use per person within a country (m3/yr)

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22
Q

What is GDP?

A

Gross Domestic Product is a measure of the monetary value of all goods and services produced within a country in a year (used as a measure of affluence)

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23
Q

What is a water footprint?

A

The volume of water needed for the production of goods and services consumed by a person or a group of people (e.g. business, country)

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24
Q

What are some abstractive uses of water?

A

Desalination, HEP, mining, transportation, heavy industry, domestic use

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25
Q

How has unsustainable exploitation affected the Mekong River?

A

Increasing water demand due to population rise and agricultural use has caused pressure on the fishing industry (largest inland fishing industry in the world) as well as water scarcity

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26
Q

What is a reservoir and why are they built?

A

An artificial lake in which water is stored (dams are built to control the volume of water leaving the reservoir)

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27
Q

What are the advantages of reservoirs?

A
  • Water security during droughts
  • Stores for irrigation
  • HEP generation
  • Improves sanitation in urban areas
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28
Q

What are the disadvantages of reservoirs?

A
  • Large land requirement
  • Human displacement and relocation
  • Alters fish migration patterns
  • Micro-climatic changes
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29
Q

How do reservoirs cause habitat change?

A

The area upstream of a reservoir is flooded and becomes a freshwater habitat, whereas the area downstream of a reservoir becomes a dry habitat

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30
Q

How do reservoirs create wildlife barriers?

A

The natural flow of a river is prevented which creates a migration barrier for marine organisms, especially fish which would normally travel upstream to spawning grounds

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31
Q

How do reservoirs cause changes in river flow?

A

Less water arriving downstream may cause the river to reduce in size (impact on water availability)

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32
Q

How do reservoirs cause sedimentation?

A

Suspended material settles and builds up behind the dam as regular river flow is prevented (reduced reservoir capacity and nutrient availability downstream)

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33
Q

How do reservoirs cause micro-climatic changes?

A

Water affects local abiotic factors as it has a high specific heat capacity and retains thermal energy for a long period of time (moderates temperature extremes)

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34
Q

What are the examples of micro-climatic changes caused by a reservoir?

A
  • Warmer than surrounding areas in winter
  • Cooler than surrounding areas in summer
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35
Q

Which factors affect reservoir location?

A

Topography, geology, catchment area, water supply, existing land use, pollution risk, sedimentation, infrastructure

36
Q

What is the ideal topography for a reservoir?

A

A valley with steep sides and a river (or a natural depression in the ground)

37
Q

What is the ideal geology for a reservoir?

A

Impermeable rock base to prevent reservoir drainage (e.g. granite, clay)

38
Q

What is a river’s catchment area?

A

The area where all runoff will flow into a particular river

39
Q

What is the ideal catchment area for a reservoir?

A

A larger catchment area will increase the volume of water which is transferred to the reservoir

40
Q

What is the advantage of a large catchment area?

A

Water will still flow through runoff into the river and reservoir during dry periods with little precipitation

41
Q

What is the ideal water supply for a reservoir?

A

High levels of precipitation

42
Q

What is the ideal existing land use for a reservoir?

A

Not located on or near existing designations, urban areas and agricultural land

43
Q

Why must pollution risk be taken into account when siting a reservoir?

A

Chemical runoff from agriculture may concentrate in the reservoir due to runoff from farmland

44
Q

Why must sedimentation be taken into account when siting a reservoir?

A

The amount of soil erosion within the catchment area should be low in order to reduce sedimentation (increased vegetation reduces soil erosion)

45
Q

What is the ideal infrastructure for a reservoir?

A

Existing roads which would reduce the cost of new access roads to the reservoir

46
Q

What is an estuary barrage?

A

A dam built across the mouth of a river which prevents freshwater reaching the ocean
- Migration barrier
- Prevents maritime transport
- Affects inter-tidal zones which may be legally protected by a designation

47
Q

What is an aquifer?

A

A body of permeable rock which stores and transmits groundwater

48
Q

What are the 3 main features of aquifer formation?

A
  • Porosity
  • Permeability
  • Suitable geological structures
49
Q

Why is porosity required for aquifer formation?

A

It is a measure of the proportion of a rock’s volume that is empty space and could store water

50
Q

Why is permeability required for aquifer formation?

A

It is a measure of the ease of water flow through a rock due to pathways between spaces which allow for the downward movement of water into the aquifer

51
Q

What are the suitable geological structures required for aquifer formation?

A
  • Impermeable rock beneath the aquifer to prevent drainage
  • Syncline basin on which the aquifer sits (curved)
52
Q

What are some examples of porous and permeable rocks?

A

Chalk, limestone, sandstone

53
Q

What are some examples of impermeable rocks on which an aquifer could sit?

A

Clay, granite

54
Q

What are the 2 types of aquifer?

A
  • Confined aquifer - situated between two layers of impermeable rock
  • Unconfined aquifer - exposed to the surface and can be directly recharged
55
Q

What is an artesian well?

A

A well that transports groundwater to the surface using hydrostatic pressure (no pumping required)

56
Q

What is the water table?

A

The upper limit of groundwater within Earth’s surface (the boundary between the saturated zone and the unsaturated zone)

57
Q

What are the 5 main consequences of aquifer overuse?

A
  • Reduced groundwater supplies
  • Subsidence
  • Changes in surface hydrology
  • Ecological impacts
  • Saltwater incursion
58
Q

What are the impacts of reduced groundwater supplies?

A
  • Limited supplies for agriculture, domestic and industrial use
  • Reduced food production and security
  • Negative economic impacts (decreased GDP)
59
Q

What is subsidence?

A

The downward movement of sediment and rocks, caused by the loss of hydrostatic pressure in the aquifer which leads to pores becoming empty and compacting

60
Q

What are changes in surface hydrology?

A

Disappearance of surface water features if the water table drops (loss of lakes, rivers, ponds, wetlands)

61
Q

What are the ecological impacts of aquifer overuse?

A
  • Loss of freshwater habitats due to changes in surface hydrology
  • Extinction of endemic species
  • Species migration
  • Loss of inter-species relationships
62
Q

What is saltwater incursion?

A

Aquifer overuse in coastal areas causes the rock to draw in water from stores of salt-water in the ocean as the water table drops below sea level

63
Q

Why is saltwater incursion particularly damaging?

A
  • Groundwater has the longest RT of any reservoir (5000 years) and therefore salt water incursion may cause long-term contamination
  • Water is unsuitable for irrigation and could kill crops through osmotic dehydration
64
Q

Which 2 methods are used for monitoring aquifer water levels?

A
  • Boreholes - physically monitor the height of the water table and can be compared to previous years
  • GRACE satellites - Gravity Recovery and Climate Experiment
65
Q

How do GRACE satellites work?

A

They carry out gravity surveys
- Increased mass below the surface increases gravitational pull (and vice-versa)
- An increase in mass indicates an increase in volume of water in the aquifer

66
Q

What is a cone of depression?

A

A depression in the water table caused by over-abstraction around an artesian well

67
Q

Which is the most important aquifer in the UK?

A

The London Basin - a confined aquifer in SE England with a reservoir rock of chalk and a base rock of clay

68
Q

What is aquifer recharge?

A

The natural replenishment of groundwater stores in aquifers (mainly due to precipitation)

69
Q

What are 2 examples of over-exploited aquifers?

A
  • North China Plain - large scale irrigation has led to over-exploitation, causing subsidence and loss of surface water features
  • Malta - lack of freshwater resources has led to over-exploitation, causing saltwater incursion and threats to food security
70
Q

What are 3 examples of exploitation of new sources of water?

A
  • Rainwater collection
  • Rivers
  • Seawater
71
Q

What are the advantages of rainwater collection?

A
  • Reduces urban flooding
  • Provides water to rural areas with no public water supply
72
Q

What are the 4 main features which affect the usefulness of a river?

A
  • Total annual river discharge
  • Flow fluctuations
  • Levels of natural contaminants
  • Human activity pollutants
73
Q

What is the disadvantage of seawater?

A

Desalination is very energy-intensive and expensive

74
Q

What are the 6 ways in which water can be sustainably managed?

A
  • Artificial recharge of aquifers
  • River-regulation reservoirs
  • Inter-basin transfers
  • Unexploited aquifers
  • Afforestation
  • Water conservation
75
Q

What is artificial aquifer recharge?

A

The use of surplus water during periods of high rainfall to replenish groundwater stores

76
Q

What are river-regulation reservoirs?

A

Dams can be operated to either decrease or increase the flow of water in a river during periods of high or low levels of precipitation

77
Q

What are inter-basin transfers?

A

Water can be transferred from regions of water surplus to regions in demand (e.g. Wales to England)

78
Q

What effect does afforestation have on the water cycle?

A
  • Reduces soil erosion
  • Increases interception which decreases runoff into rivers (prevents flooding)
79
Q

What are some examples of water conservation?

A
  • Low-water appliances
  • Drip irrigation
  • Use of recycled ‘grey-water’
  • Water meters
80
Q

How is litter removed from contaminated water?

A

Water is passed through screens (metal grids) to remove large items such as plastics

81
Q

How are suspended solids removed from contaminated water?

A
  • Sedimentation (water is stored for a number of days in large tanks to allow suspended particles to settle and then be collected)
  • Flocculation (chemicals are added to neutralise the charge of suspended solids that have not settled such as clay)
82
Q

How are metals removed from contaminated water?

A

An ion exchange resin such as zeolite is added and metals such as lead, mercury and arsenic adsorb onto it

83
Q

How are organic pollutants removed from contaminated water?

A
  • Activated carbon filters (use of fine C particles which have been treated at a high temperature to remove pesticides through adsorption)
  • Aeration (water is bubbled through the water which encourages aerobic bacteria to breakdown organic matter)
84
Q

How is salt removed from contaminated water?

A

Desalination:
- Reverse osmosis (water is forced through a semi-permeable membrane - energy intensive)
- Distillation (Water is heated to allow evaporation and water vapour is condensed and collected)

85
Q

How are pathogens removed from contaminated water?

A

Sterilisation is used to remove pathogens which could cause disease (using either O3, Cl or UV)

A Level Environmental Science (23 decks)

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