1
Q
What does it mean that the water cycle is a closed system?
A
- Inputs and outputs move to and from stores within the system. None crosses the systems boundaries.
- the amount of water in the water cycle is fixed, which means the mass balance does not change
- water is held in stores in, on and above earth
- flows are transfers of water between stores
2
Q
What are the 6 major water stores?
A
- oceanic
- cyrosphere
- groundwater and soil moisture
- terrestrial surface water
- atmosphere
- biosphere flora and fauna
3
Q
What is the cryosphere?
A
Any place on earth where water is frozen.
4
Q
What is permafrost?
A
Ground permanently frozen for over 2 years
5
Q
What is eustatic change?
A
The global change in the volume of water in the oceans
6
Q
What is meant by ‘accumulation’?
A
The build up of snow and ice in the cyrosphere
7
Q
What is meant by ‘ablation’?
A
Change of ice into liquid or water vapour.
8
Q
How can sea level change change the size of water stores?
A
- eustatic change has resulted in sea levels changing significently over geological time
- during glacial periods more water is frozen, decreasing water in the oceans
- climate warming increases ice sheet melting, raising sea levels
9
Q
How has changes in cryosphere processes changed the size of water stores?
A
- short term changes in ice accumulation and ablation occur annually due to seasonal changes in temperature
- climatic changes, resulting in glacial and interglacial periods, cause significant changes in the cryosphere
- human induced global warming may be permanently reducing the cryosphere by increasing ablation
10
Q
What are the processes that control transfers in the water cycle across a range of timescales?
A
- short term storm events increase transfers locally
- seasonal variations in climate impact on transfer rates
-climatic variability due to events lasting years such as El Nino Southern Oscillation impacts on precipitation levels - global warming impacts on precipitation levels and evaporation rates, influencing flows between the land and the atmosphere
- climate change impacts on ablation rates, affecting transfers between the cryosphere and other parts of the system
11
Q
What is a drainage basin?
A
An area of land drained by a river and its tributaries. The boundary of the basin is called the watershed.
12
Q
What is the input component of a drainage basin?
A
Precipitation
13
Q
What is precipitation?
A
Rain, snow, sleet, hail, frost: the type, amount, duration and intensity influence transfers and stores in the system
14
Q
What are the 8 flow components of a drainage basin?
A
Throughfall
Stemflow
Infiltration
Overland flow
Throughflow
Percolation
Groundwater flow
Channel flow
15
Q
What is throughfall?
A
Water dripping from plants to the ground; rate is influenced by leaf cover
16
Q
What is stemflow?
A
Water flowing down stems and trunks
17
Q
What is infiltration?
A
Water soaking into the soil; infiltration rate/capacity is the rate at which water can pass into the soil; affected by soil characters
18
Q
What is overland flow and what are the 2 types?
A
Water flowing over the surface -
- saturation excess overland flow, the soil is saturated, so rainfall cannot infiltrate
- infiltration excess overland flow, rainfall intensity is so great that is exceeds infiltration capacity
19
Q
What is throughflow?
A
Slow, lateral (sideways) movement downslope through the soil
20
Q
What is percolation?
A
Downward movement from soil to underlying rock
21
Q
What is groundwater flow?
A
Slow, downward and lateral movement through bedrock
22
Q
What is channel flow?
A
Flow of water in streams and rivers
23
Q
What are the 5 store components of a drainage basin?
A
Interception store
Vegetation store
Surface store
Channel store
Groundwater store
24
Q
What is interception store?
A
Water held on leaf and plant surfaces
25
What is vegetation store?
Water contained in plants
26
What is surface store?
Water collected in depressions in the ground surface; also includes snow cover
27
\what is channel store?
Volume of water in a river channel
28
What is groundwater store?
Water stored in underground rocks, the water table marks the upper level of saturated rock
29
What are the 3 output components of a drainage basin?
Evaporation
Transpiration
Channel discharge to oceans
30
What is evaporation?
Water changing state from liquid to water vapour, it occurs from any surface store or flow
31
What is transpiration?
The release and evaporation of water from vegetation
32
What is meant by 'channel discharge to oceans'?
The volume of water leaving a drainage basin and flowing into the sea
33
What is a river regime?
Annual variations in a rivers discharge, a line graph showing the changes is called a hydrograph
34
What is baseflow of a river?
Water entering from groundwater creates a normal minimum flow
35
What is stormflow of a river?
Water entering by overland flow and throughflow after precipitation creates storm flow
36
What is a simple river regime?
One high and one low discharge corresponding to seasonal temperature and precipitation changes
37
What is a complex river regime?
Several extremes of discharge in a year
38
What are the physical factors influencing river regimes?
- climate (annual precipitation pattern, seasonal variations in temperature, evaporation rates)
- vegetation
- soil
- geology
39
What are the human factors influencing river regimes?
- land use
- irrigation and use of water
- dam construction, creating reservoirs to store water and even out the flow through the year
40
What is a storm hydrograph?
Shows a rivers response to a precipitation event
41
What are the 5 features of a storm hydrograph?
peak discharge
peak rainfall
lag time
rising limb
recessional (falling) limb
42
What is the peak discharge of a hydrograph?
Maximum rate of flow
43
What is the peak rainfall of a hydrograph?
The time of the maximum rainfall
44
What is the lag time of a hydrograph?
The period between peak rainfall and peak discharge
45
What is the rising limb of a hydrograph?
Part of the graph showing increase in discharge
46
What is the recessional (falling) limb of a hydrograph?
Shows the decreasing discharge
47
What is a flashy hydrograph?
Has a short lag time, high peak discharge, and steep rising and falling limbs
48
What are the 3 climatic factors affecting hydrographs?
Rainfall intensity and duration
Antecedent weather conditions
Temperature
49
How does rainfall intensity and duration affect hydrographs?
Heavy or prolonged rainfall increases overland flow, resulting in a flashy hydrograph
50
How does antecedent weather conditions affect hydrographs?
Previous rainfall may saturate the ground, so overland flow occurs quickly
51
How does temperature affect hydrographs?
Influences evapotranspiration, affecting the amount of water available to reach the channel; frozen grounds prevents infiltration shortening lag times
52
What are the 6 river catchment characteristics affecting hydrographs?
Basin size and shape
Drainage density
Geology and soils
Slope angle
Type and amount of vegetation
Land use
53
How does basin size and shape affect hydrographs?
Larger drainage basins have a longer lag time; circular basins drain more quickly
54
How does drainage density affect hydrographs?
HIgher densities have shorter time lags and higher peak discharge
55
How does geology and soils affect hydrographs?
Permable rocks allow more percolation and ground water, decreasing overland flow and discharge
Soil type and depth influence infiltration and throughflow, affecting overland flow and lag time
56
How does slope angle affect hydrographs?
Steeper slopes reduce infiltration, increase overland flow and shorten lag times
57
How does type and amount of vegetation affect hydrographs?
Influences interception, vegetation store and transpiration rate, affecting overland flow and lag times
58
How does land use affect hydrographs?
Artificial, impermable surfaces increase overland flow, reducing lag times
Agricultural practices, such as compaction of soil by animals or machinary, or leaving land uncultivated, can influence infiltration rates
Construction of dams and reservoirs reduces peak discharge
59
What 3 methods of air uplift result in precipitation?
- orographic
- frontal
- convection
60
What is orographic uplift?
Air is forced to rise over higher land
61
What is frontal uplift?
When air masses of different temperatures meet, the warmer less dense air rises over the cooler air mass
62
What is convection uplift?
Daytime heating of the ground warms air in contact with it, forcing it to rise
63
How are clouds formed?
Rising air expands, resulting in cooling
When it cools to its dew point, water molecules condense around small particles (condensation nuclei) forming clouds
64
What are the 2 theories of precipitation formation?
Collision coalescence process
Bergeron-Findeisen process
65
What is the collision coalescence process?
In warm tropic areas, water condenses around large condensation nuclei
Larger droplets fall to earth, colliding with smaller droplets and absorbing them
66
What is the bergeron findeisen process?
High altitude clouds with temperature below 0* contain ice crystals and super cooled water droplets
The ice crystals grow as water evaporates off the droplets and deposits on the ice
The ice crystals gain weight and fall as snow flakes
Snowflakes melt in warmer air layers, forming rain
67
What are the 5 causes of excess runoff generation?
Prolonged precipitation
Intense storms
Monsoon rainfall
Snowmelt
Human causes
68
How does prolonged precipitation cause excess run off generation?
Results in saturation excess overland flow
69
How does intense storms cause excess runoff generation?
Result in saturation excess and infiltration excess overland flows
70
How does monsoon rainfall cause excess runoff generation?
Similiar impact to prolonged and storm precipitation in areas of monsoon climate
71
How does snowmelt cause excess runoff generation?
Melting of accumulation of snow and ice results in saturation excess of overland flow, especially if the ground is frozen
72
What are the human causes causing excess runoff generation?
- urbanisation makes the surface impermable, reducing infiltration and the soil moisture store. Drainage transports water quickly to rivers, reducing lag time, less vegetation reduces evapotranspiration, increasing runoff
- river basin mismanagement can increase the amount of runoff. As already seen, urbanisation increases runoff. Another example of major mismanagment is large scale deforestation, removal of trees increases runoff
- loss of flood plain storage due to chanelling and the construction of dykes for flood management results in increased runoff, creating potentially bigger floods downstream
- staightening and canalisation of rivers speeds up the flow increasing runoff downstream
73
What are the 3 types of drought?
Meteorological drought
Agricultural drought
Hydrological drought
74
What is meteorological drought?
An extended period of lower than average rainfall for the region
75
What is an agricultural drought?
Insufficient moisture to maintain crop yields
76
What is hydrological drought?
Shortages in water supplies in surface and groundwater stores
77
What are the meteorological causes of deficit in the water cycle?
- seasonal precipitation variations result in soil moisture deficit
- El Nino Oscillation (ENSO) impacts on weather patterns around every 7 years, resulting in meteorological drought in some regions
- climate change results in long term declining precipitation and meteorological drought
78
What are the human causes of water depletion?
Aquifer depletion - water is extracted from groundwater stores for human use faster than it is replenished, which can reduce water levels in rivers and lakes
Surface store depletion - the use of water reduces river discharge and the size of inland bodies of water
79
What are the modern human uses for water?
- domestic water consumption
- irrigation of crops
- industrial use
80
How can aquifers be recharged?
Natural recharge - reducing extraction allows recharge by the percolation of precipitation and surface water to the aquifer
Artificial recharge - water is added to the ground surface, or pits and basins are flooded, increasing percolation rate, injection wells where water is pumped into the aquifers via a well
81
What is the carbon cycle?
Biochemical cycle in which carbon moves between the lithosphere, oceans and the atmosphere
82
What are carbon fluxes and residence time?
A flow between stores is also known as a flux
The residence time is the time carbon is held in a store
83
What are the 5 carbon stores?
Lithosphere and sedimentary rocks
Oceans
Fossil fuels
Biosphere
Atmosphere
84
What are the 4 carbon processes between the land and the atmosphere?
Fossil fuel combustion
Carbon sequestration and photosynthesis
Respiration
Decomposition
85
What is a fossil fuel combustion?
Burning coal, oil and gas releases carbon dioxide into the environment
86
What is carbon sequestration and photosynthesis?
Sequestration - carbon dioxide is removed from the atmosphere and held in solid or liquid form
Photosynthesis- plants use light, water and carbon dioxide to produce glucose and oxygen
87
What is respiration?
Living organisms produce energy through glucose and oxygen reacting together , resulting in carbon dioxide being released into the atmosphere
88
What is decomposition?
When organic matter dies it breaks down by physical, chemical and biological processes, which releases carbon dioxide into the atmosphere
89
What are the 2 carbon pathways between the ocean and the atmosphere?
Absorption by biota
Diffusion into and out of oceans
90
How does absorption by biota result in a carbon pathway between the ocean and the atmosphere?
Phytoplankton absorbs carbon dioxide by photosynthesis, which passes through the marine food chain when the phytoplankton is eaten. Some carbon end ups in sediments when dead organisms settle on the seabed.
91
How does carbon diffuse in and out of oceans?
Where the ocean is in contact with the atmosphere, carbon dioxide is absorbed by the water
Cold water sinking transfers the carbon to the deep ocean. Water moving to the surface and warming loses carbon dioxide to the atmosphere
92
What are the 4 carbon pathways between the land and oceans?
Weathering
River transport and indirect movement by the water cycle
Carbon sequestration
Earth movements
93
How does weathering act as a carbon pathway?
Particles of rock are carried to the oceans and deposited. The chemical weathering process of carbonation dissolves the calcium carbonate in rocks, changing minerals containing lime into soluable bicarbonates that are carried by water to the oceans. There it is used by organisms to create shells, which forms deposits when the organisms die, eventually creating a rock carbon pool storing carbon for millions of years
94
How does river transport act as a carbon pathway?
Channel flow, through flow and groundwater flow move dissolved calcium carbonate into oceans
95
How does carbon sequestration act as a carbon pathway?
Deposited sediments build up over time, forming new carbon pools of sedimentary rocks
96
How does earth movements act as a carbon pathway?
Sediments are uplifted above sea level, where the weathering process starts again
97
What is a biome?
A major community of plants and animals adapted to the characteristics of the environment, especially climate
98
What is Net Primary Productivity?
NPP is the dry weight of biomass added per unit area per year
99
Where can carbon be stored in biomes?
- the biomass above and below ground
- dead organic matter on the surface (leaf litter)
- the soil
100
What are the 4 factors influencing carbon storage?
Temperature
Precipitation
Light
Influence on the carbon stores
101
Compare the temperature in a tropical rainforest and temperate grassland.
Tropical rainforest - average annual temperature is 25*/30*, minimal seasonal variation
Temperate grassland - high temperature range during the year; +40* to -30* are possible
102
Compare the precipitation in a tropical rainforest and temperate grassland.
TR - high average annual rainfall, over 2000mm, no dry season; convectional rainfall most days
TG - low average annual rainfall, 500mm or less, spread throughout the year; snow in winter
103
Compare the light in a tropical rainforest and temperate grassland.
TR - suns rays concentrated; little seasonal variation
TG - seasonal variation in solar radiation
104
Compare the influence on the carbon stores in a tropical rainforrest and temperate grassland.
TR - year round plant growth and high levels of biomass, atmospheric carbon sequestration is high all year, decomposition is rapid, returning carbon quickly to the soil, high rainfall leaches the soil removing carbon
TG - atmospheric carbon sequestration varies with seasonal plant growth, humid conditions in autumn allow rapid decomposition and return of carbon to the soil, lower rainfall prevents leaching, allowing a larger soil carbon pool
105
What human acitivities can cause changes in the size of carbon stores due to human activity?
Deforestation
Afforestation
Agricultural acitvity
106
How does deforestation affect the size of carbon stores?
- removes biomass carbon store
- crops replacing trees have less biomass, reducing store size
- decomposition is reduced, lessening input to the soil store
- unprotected soil is vulnerable to erosion, reducing soil store capacity
- burning biomass increases carbon dioxide transfer to the atmosphere
107
How does afforestation affect the size of carbon stores?
- increases carbon sequestration and biomass store
- reduces soil erosion, maintaining the soil pool
108
How does agricultural activity affect the size of carbon stores?
- clearing areas for agriculture reduces carbon storage
- soil degradation from poor practice causes soil erosion, reducing storage capacity
- harvesting removes biomass store
- over irrigation leaches soil, removing carbon
- fertiliser and manure increase carbon in the soil store
- machinary increases carbon dioxide emissions
109
What is meant by 'anaerobic' conditions?
occur in areas with little or no oxygen, such as water logged soils
110
What is peat?
Accumulation of partly decomposed organic matter, forming a deposit on boggy, acidic ground. It forms in low relief areas at both high and low altitudes (the former due to high orographic precipitation; the latter due to soil water movements)
111
How is peat formed?
- dead wetland plants do not fully decay in wet, anaerobic conditions, which prevent bacteria from decomposing dead material, allowing it accumulate
- organic matter is compressed into a peat layer that can be many metres thick
- accumulation is 1mm/yr, many bogs are thousands of years old
- peatlands globally store double the amount of carbon stored in forests
- the organic matter is 50% carbon
- UK peatlands hold the equivalent of 3 years of UK carbon emissions
112
What is peat burning and drainage?
Burning - peat is dried and used as fuel in some rural areas and power sections. This releases carbon dioxide into the atmosphere store
Drainage - allows use of peatlands for agriculture, increases the decomposition rate, releasing more carbon dioxide. it increases flow of carbon to rivers. Drained areas may be afforested, changing the biomass carbon store
113
How is peatland restored?
Blocking drainage channels - increases infiltration and raises the water table, increasing water logging and anaerobic conditions
Creating berms - prevents drainage
Clearing invasive vegetation and re-establishing wetlands plants
Adopting the 'peatland code' - encourages investment in restoration of UK peatlands
114
Why have carbon emissions almost doubled since 1750?
- increasing fossil fuel use resulting from population growth and increasing economic growth
- deforestation (carbon dioxide)
- increased livestock (methane)
- decomposition from increasing landfill (methane)
115
What is the energy budget?
The balance between energy received from the sun and energy radiated back into space
116
What is the greenhouse effect?
- 70% of solar energy reaching earth is re-radiated back as long wave radiation, much of this is absorbed by the atmosphere
- increasing carbon dioxide and methane in the atmospheric store retains more heat, creating the greenhouse effect
- increasing temperature raises water vapour levels, which further increases temperature
117
How does increases in carbon stores affect precipitation and extreme weather?
- higher temperatures increase evaporation, potentially increasing precipitation
- increasing temperatures could lead to more heavy convectional rainfall
- in europe, precipitation may become more seasonal
- evidence suggests an increase in extreme precipitation events, heat waves and droughts, wetter regions may experience increased precipitation
- hurricanes and tornados could increase in intensity
- the IPCC has projected that global surface temperatures will rise by more than 1.5* by the end of the 21st century, causing the global water cycle to change, with increasing differences between wet and dry regions
118
How does increases in carbon store affect river discharge?
- intense rainfall causes infiltration excess overland flow, rapidly increasing discharge and flooding potential
- the river regime adjusts to precipitation changes
119
How does increases in carbon store affect sea levels?
- warmer climate increases ice sheet melting, producing eustatic sea level rise
- warming of oceans expands the volume of water
- sea level is rising by 3.5mm/yr
120
How does increases in carbon stores affect acidification of the oceans?
- increase in atmospheric carbon allows more carbon to diffuse into the oceans, creating carbonic acid
- shell building animals have thinner shells
121
What are the links between the water and carbon cycles at the local scale?
- the cycles link where the carbon is transported (dissolved or as sediment) in water
- changing biomass store impacts on movement in the water cycle (eg deforestation)
- irrigation alters water cycle flows and NPP; influencing carbon sequestration
- overgrazing and land degration allow soil erosion , lowering infiltration rates and soil moisture stores, meaning lower carbon sequestration and storage
122
What is steady-state equilibrium?
Long term average state of balance, despite changes occuring within it
123
What is positive feeback?
The initial change causes further damage
124
What is negative feedback?
The change is reduced, restoring equilibrium
125
Give positive and negative feedback for increased carbon in the cryosphere.
Increased temperatures, sea ice and ice caps melt, land and sea have lower albedo and absorb more heat
+ atmospheric temperatures rise, melting more ice
- increased evaporation and cloud cover reflect solar energy, sea temperature drops, cooling air in contact with it and decreases melting
126
Give positive and negative feedback for increased carbon in terrestrial settings.
Global temperatures rise
+ warming tundra areas, increasing decomposition, increasing co2 in the atmosphere raising temperatures
- coniferous forest biome migrates northwards and expands, biomass co2 store expands
127
What is marine carbon feedback?
- warmer oceans releasing more carbon dioxide contribute further to climate warming
- acidification impacts on the health of marine ecosystems, which reduces carbon sequestration and can impact on the biological ocean pump
128
What is methane feedback?
- large amounts of methane are stored in permafrost. This is released when climate change causes melting
- increased methane raises the atmospheric temperature, melting more permafrost
- the impact could take earths climate past its threshold point
129
What are the implications of feedback within and between the two systems for life on earth?
- climate change impacts on vegetation patterns, influencing food production
- melting ice caps cause eustatic sea-level change, leading to the flooding of low-lying coastal areas, where major cities are located
- reduction in ice reduces annual meltwater supply, which decreases water supplies for some major cities
- extreme weather events cause more damage and loss of life
- climate change causes diseases to spread to new areas
- ocean temperature changes affect circulation patterns, thereby influencing climates
- new areas become suitable for cultivation
130
A2 Geography
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