Physical - Water and carbon cycles Flashcards
What is a system?
A set of interrelated components working together
What are inputs (in systems)?
Material or energy entering a system
What are outputs (in systems)?
Material or energy moving out of a system
What are stores in systems?
A part of a system where energy/mass is stored or transformed
What are flows and transfers?
Links or relationships between components in a system
What are elements/components (in terms of systems)?
Parts of a system
What are attributes in systems?
Characteristics of elements in system (eg volume, temp, colour etc)
What are relationships in systems?
Links between the elements and attributes of systems (cause and effect)
What is an open system?
A system whereby inputs and outputs move through a system
What is a closed system?
A system whereby energy is transferred, but not matter
What is an example of a closed system?
Earth (mostly) - energy from sun or radioactive decay of earths core is transferred but mass is conserved
What is an isolated system?
A system which has no interactions with anything outside the system boundary
Give 2 examples of inputs of the global water cycle
- Precipitation
2. Interbasin transfer
Give 2 examples of outputs of the global water cycle
- Transpiration
2. Interbasin transfers (again)
What is dynamic equilibrium?
The balanced state of a system, when inputs and outputs are equal.
What is positive feedback?
Where the effects of a change in a system are amplified by changes to inputs/outputs/processes.
The state of the system moves away from dynamic equilibrium.
What is negative feedback?
Where the effects of a change in a system are nullified by changes to inputs/outputs/processes.
The system moves closer to a state of dynamic equilibrium.
What are the 4 (6) subsystems on earth?
- Lithosphere (includes pedosphere)
- Hydrosphere (includes cryosphere)
- Atmosphere
- Biosphere
Where is permafrost found?
In areas of tundra in N. America and Euroasia
Compared to CO2, how much methane is there stored in the permafrost?
Double the amount of CO2 currently in the atmosphere
By how much have temperatures in northern Alaska increased each year since 2005?
By 0.1C each year
Why is Climate Change a concern for Western Europe?
Upsets the dynamic equilibrium of the North Atlantic Thermohaline Circulation system because of more cold fresh water entering the north Atlantic. This could stop the gulf stream
What % albedo does sea ice have?
80% albedo, very high
How much of the water on Earth is in the oceans?
97%
How much of the water on Earth is in the glaciers?
2%
How many times has the water we drink been drunk before?
7 times!
How much water on Earth is freshwater?
2.5%
How much freshwater on Earth is accessible?
1.2% (not ice)
How many valley glaciers are there in the Himalayas?
15,000
Why is the melting of sea ice not a concern? But why is it useful?
Sea ice consists of sea water, so it does not contribute to sea level rise. However, the melting of sea ice is a very good indicator of climate change at the poles.
What are ice shelves?
Platforms of ice that form where freshwater ice sheets or glaciers move into the ocean
What are ice sheets?
A mass of glacial land extending over 50,000 km2
How much volume does the Antarctic ice sheet make up?
30 million km3
What is the slow water cycle?
Water percolates/infiltrates deep into the lithosphere (bedrock) and is stored for >1000 years
What is the fast water cycle?
The familiar version of the water cycle. Water evaporates and precipitates
Why are some of the largest Aquifers found beneath the Sahara?
They as “fossil” aquifers - remnants of previous, cooler climates
How much of the surface of the Earth is covered by oceans?
72%
What are the 4 types of terrestrial water?
- Bio water
- Soil water
- Surface water
- Groundwater
How many lakes there there in Canada?
3 million
How much of the Arctic is classified as wetland?
60%
Name a plant which unusually uses water for strength, not storage.
The Baobab tree
How much of La Paz’ water supply comes from glaciers?
15% (up to 30% during dry season)
How much electricity in Columbia relies upon the melting of glaciers?
70% (hydropower)
What are aerosols?
Small particles of salt and dust (condensation nuclei)
What happens when the air becomes saturated with water?
Clouds form (cannot hold any more water vapour)
What is the condensation level?
The height at which DEW POINT is reached and clouds form
What is orographic (relief) rainfall?
Air mass containing water rises over higher terrain and condenses. Rain clouds form above orographic clouds and rain drops fall and get larger as they combine.
How does frontal rain occur?
At a cold front, cold air advances beneath a warm front, causing the warm air to rise and cool.
Leads to heavy rainfall and thunderstorms in summer
What is the definition of Albedo?
The reflection coefficient - a measure of how reflective a surface is
For how long is water stored in shallow groundwater stores?
100-200 years. 10,000 years for deep aquafers
For how long is water stored in glacial stores?
20-100 years
What is accumulation?
The build up of ice mass following persistent snowfall
What is ablation?
The loss of ice mass through melting
Why do phytoplankton accumulate behind icebergs?
Icebergs carry nutrients needed for organisms, such as iron.
How do icebergs get nutrients needed for phytoplankton growth?
Glacial erosion, picking up rocks
How much land did ice cover 18,000 years ago?
1/3 land in the last ice age
How much lower was sea level during the last glacial period?
100 metres lower
At the peak of previous intergalcial periods, how much higher were sea levels worldwide?
Up to 50 metres high
What is channel flow?
The flow of water through a drainage basin system in rivers
What is stem flow?
The flow of water through a drainage basin system in plant stems/ xylems
What is a drainage basin?
The total area drained by a river and its tributaries, bordered by the watershed.
What is a watershed?
Either:
A shed full of water
OR
The edge of a drainage basin (highest land normally)
How much of the world’s water is stored in the Greenland ice sheet?
8% of the global freshwater
How deep is the Greenland ice sheet?
2km deep
If all of the Greenland ice sheet melted by how much would sea levels rise?
By 7.2 metres
When did an early ice melting event occur in Greenland?
In mid-April 2016 and 2012
Why is snowfall important in the water cycle?
Fresh(er) snow cover has an albedo of 90% whereas older snow cover contains darker sediment, accelerating melting of ice sheets
How much of the worlds population live in a coastal zone?
1/3 global population
How long is the River Wye?
215km
What factors of the river Wye drainage basin increase river discharge?
- Steep upland slopes
- No woodlands in upper course
- Ditches have been dug
- Impermeable mudstones in upper course
What is water transfer?
The movement of water through a drainage basin system along tributaries or even man-made ditches and drains
When does the RIver Wye have surplus storage?
In the winter months (highest in January)
What is soil moisture depletion?
When a water store is used by plants
What is a soil moisture deficit?
When there is insufficient water for plants
What is soil moisture recharge?
When soil water begins to increase (but still a deficit) following rainfall
What is the equation for calculating water balance?
P = O + E + S Precipitation = Runoff + Evapotranspiration + Storage
Give an example of a flood event on the River Wye?
Herefordshire floods 2007
When did a drought occur on the River Wye?
In 2012 and 2018
How low did water levels on the river Wye get in July 2018? Why?
‘Lowest levels in 30 years’. Leisure and tourism, close proximity to Hereford and Birmingham where there is more demand for water, thus more extraction
How much of the water stored in the Atmosphere was transferred by evapotranspiration?
10%
What is discharge?
The volume and speed of water at a give point on a river
What is important to note about discharge?
It is NOT the same at all points on a river - only a SNAPSHOT
Why does discharge increase downstream on rivers?
There is greater volume due to water being inputted into the river systems from surrounding tributaries. This also increases the velocity of the water
Why is studying discharge important?
Gives insight into:
- Flash flood warnings
- ‘Slow’ flooding
- Erosion rates
- Stresses on infrastructure along rivers (mills, bridges etc)
What is a river regime?
The variability of river discharge throughout a year (a graph showing discharge over a year)
Where is discharge in rivers consistently measured in the UK?
At 1,500 drainage basin network stations
Why is discharge measured at so many locations in the UK?
The UK has a very variable climate, topography, geology and land use
How much rainfall does some parts of Scotland receive in a year?
5 metres. This highlights the importance of multiple drainage basin network stations in the UK because some parts of Essex receive very little rainfall.
What are the 6 components of a storm hydrograph?
- Peak rainfall
- Lag time
- Rising limb
- Peak discharge
- Falling limb
- Normal/base flow
What is “peak rainfall” on storm hydrographs?
The hour with the greatest rainfall during a strom
What is “lag time” on a storm hydrograph?
The period of time between peak rainfall and discharge - the amount of time taken for water to travel into a river from across a drainage basin
What are the “rising” and “falling” limbs on a storm hydrograph?
The period of time when discharge rises and falls respectively
What is base/normal flow on storm hydrographs?
The discharge/flow along a river under normal conditions
What is a soil moisture graph?
A graph to show variation in soil moisture over a year depending on rates of precipitation and evapotranspiration as inputs and outputs respectively of the system
Name some physical factors which affect storm hydrographs?
- Size and shape of drainage basins
- Drainage density
- Relief
- Duration and intensity of rainfall
- Type of precipitation
- Permeability of rocks
- Vegetation cover
- Soil texture
[all regarding drainage basins]
Name some human factors which affect storm hydrographs
- Deforestation
- Growth of urban areas
- Dams
- Ploughing
- Other agricultural practices
How does a large drainage basin affect storm hydrographs?
More precipitation “captured” so peak discharge is higher
What shape of drainage basin causes the flashiest storm hydrographs?
Circular drainage basins - shorter “radius” to a river
What is meant by drainage density?
The number of tributaries in a drainage basin (more rivers = higher drainage density)
How can the length of rainfall affect storm hydrographs?
Long-duration rainfall causes a more flashy flood hydrograph with a higher peak discharge
How can the type of precipitation affect storm hydrographs?
Rain = short lag time.
Snow = long lag time because snow takes time (days-months) to melt.
If the same volume of water is inputted into the system the peak flow will be the same.
How has the growth of urban areas affected storm hydrographs?
- More impervious and impermeable surfaces
- Less green areas and vegetation to intercept rainfall
Interception and infiltration decreases, runoff increases
How many hectares of Garden have been converted into impermeable areas in London between 1998 and 2006?
300 ha/year
How can a closed dam affect a flood hydrograph?
Flow is regulated so only normal flow occurs when closed
If a dam is opened what happens to a storm hydrograph?
Becomes flashy because water quickly enters the river
How do agricultural practices affect storm hydrographs?
- Cattle trample on fields which can compact the soil so infiltration is reduced and runoff increases
- Ploughing can loosen the soil, increasing rates of infiltration, however grooves channel water, increasing runoff and water transfer dramatically
What is the name of the flood management project being undertaken at Pickering, Yorkshire?
“Slowing the flow at Pickering”
What are the aims of the ‘slowing the flow at Pickering’ project?
To demonstrate how better land management can help manage flooding using soft engineering strategies
How many times in the last 20 years has Pickering been flooded?
4 times
1999, 2000, 2002, 2007
How much £ damage did the 2007 Pickering flood cause?
£7 million
Why is the management at Pickering easy to do?
A third of the land in the drainage basin is public owned so it is easy to implement strategies and investigate how effective they are.
By how much has the chances of a flood occurring in Pickering fallen following ‘slowing the flow project’?
From 25% chance of a flood in a given year to a 4% chance
How have locals responded to the ‘slowing the flow at Pickering’ project?
The response has generally been positive and local landowners and farmers have embraced the concept of working with natural processes
Where is Pickering located?
The southern boundary of the North York Moors National park, 17km away from the water shed of the river Derwent drainage basin
Where is the source of the River Wye?
In the Welsh mountains
Where is the mouth of the RIver Wye?
Chepstow in Gloucestershire
What two rivers meet at a confluence in Pickering?
The Pickering Beck and Gundale Beck (greatly increases discharge and flood risk)
What is the land use of the drainage basin upstream of Pickering?
- Mostly arable farmland at Oak Tree Farm
- Some sheep-grazed land
- Moorland at the watershed
What is the total area of the drainage basin upstream of Pickering?
20 sq. km
When, on average does Pickering beck experience highest rates of discharge, according the river regime?
In December (an average of 25 cumecs)
What was the average discharge on Pickering Beck between 1973 and 2007?
14.4 cumecs (gradually been increasing)
What is the all-time highest discharge on Pickering Beck? When did it occur?
40 cumecs, 2002 - caused flooding in Pickering
What 3 techniques did the ‘slowing the flow at Pickering project’ adopt?
- Construction of low-level bunds
- Creation (reestablishment) of riparian and floodplain woodland
- Restoring large, woody debris dams
What is a bund? (A technique used in Pickering)
A ‘bund’ is a stone/earth embankment used to hold back water during times of excess rainfall
Where have bunds been used in Pickering?
At Newtondale, on the Pickering beck
What is the flood storage capacity of the bunds used in Pickering?
120,000m3
What was taken into account when choosing which type of tree to plant in the Pickering drainage basin?
The soil quality was very poor so trees which intercepted water and had roots which increased the permeability of the soil were chosen
How much riparian woodland has been planted at Pickering?
30 hectares
(Pickering)
Why have large, woody dams (LWDs) been removed from rivers in the last century?
Landowners feared that LWDs could affect fish populations or human infrastructure
Why are large woody dams being used in Pickering?
- Increase flood storage
- Reconnect streams in the floodplain
How many large woody dams are there being used at Pickering?
160 LWDs being used
Has the ‘slowing the flow’ project at Pickering worked?
+ Oxford Uni assessment and storm hydrograph shows a reduction in flooding
- The project has not been proven to withstand flooding of the same magnitude as previous events (eg 2007)
What are some major benefits of the ‘slowing the flow at Pickering’ project?
- Peak discharge decreased by 20%
- Museum on ‘Beck Isle’ saved
- Lag times increased
- Homes saved from future flood events
Name 6 factors which affect the water cycle
- Seasonal changes
- Land-use change
- Deforestation
- Water abstraction
- Desertification
- Soil Drainage
How much rainforest in SA has been converted to cattle pasture?
10%
Why is water abstracted by humans?
For use in agriculture, industry or domestic purposes
What 3 effects can occur if large amounts of water is extracted from aquifers?
- Sinking water tables (leading to more dry rivers)
- Empty wells
- Intrusion of salt water
Give an example of a country which can no longer use groundwater for domestic purposes because of salt water intrusion
Malta
How low did water in the London aquifer get in the 1960s?
88 metres below sea level - lowest levels ever
By how much has the London Aquifer recovered since the 1960s? Why?
Recovered at a rate of 3m/year because brewery industry closed down in the capital
What has been set up in London to control water levels?
GARDIT
General Aquifer Research, Development and Investigation Team
By how many metres have water levels in the London Aquifer fallen in East London? Why is this of concern?
Fallen by 7 metres since 2000. The area is at risk from saline intrusion, especially with eustatic changes + sea level rise
What factors indirectly cause desertification?
- Population pressures
- Policies
- International trade
What is desertification?
- A type of land degradation that can occur in dryland ecosystems
- Initiated by humans, then accelerated by natural processes
How much land in Brazil is threatened by desertification?
200,000 sq. miles
What is the economic cost of desertification in Brazil?
$300 million/year lost
What percentage of land in Mexico is vulnerable to desertification?
70%
How much lowland forest will remain in Borneo by 2030?
33% - the rest has been lost through deforestation
Why does deforestation have global consequences in the water cycle?
- Rainforests control global precipitation patterns
- Also release Volatile Organic Compounds (VOCs) which cool the planet.
Thus deforestation causes positive feedback loops
Why is transpiration in rainforests important?
- Maintains localised humidity
- Maintains cooler temperatures
- 100 litres of water transpired is equivalent to 2 air cons worth of cooling
What are the impacts of water abstraction?
- Alters river regimes
- Lowers water tables
- Saltwater intrusion
All make water sources unsustainable
What is the largest store of carbon?
Marine sediments and rocks
How much carbon is there stored in marine sediments?
100,000 GtC
What does GtC stand for?
Gigatonnes of carbon
How much carbon is there stored in oceans?
40,000 GtC, second largest carbon store
What is the longest store of carbon?
Marine sediments - takes millions of years to form
How much carbon is there stored in the atmosphere?
750 GtC
What is a carbon sink?
A carbon store which absorbs more carbon than it releases
What is a carbon source?
A carbon store which releases more carbon than it absorbs
What is carbon sequestration?
The capture of CO2 from the atmosphere before shortly being released or stored in the long term
Why is less carbon stored in the southern hemisphere?
Droughts are more common so there is less vegetation present to sequestrate carbon dioxide.
Causes the Keeling Curve to fluctuate
Where is the majority of ‘forest carbon’ stored?
25% in Russian forests
20% in The Amazon
How much carbon is there stored in peat?
250 GtC
Where does the majority of ocean carbon accumulate? Why?
In the deep layers of the ocean because there is less penetration from sunlight which would otherwise cause photosynthesis
What are ‘fluxes’ in the carbon cycle?
Measurements of the rate of flow of Carbon between stores. Measured in g/year
What is the fast organic carbon cycle?
The cycle of carbon which lasts months-centuries involving living components
What is an example of a fast NON-organic carbon cycle?
Ocean to atmosphere exchanges
How slow is the slow carbon cycle?
Very slow. Takes millions of years
What are the 3 general scales of the carbon cycle?
- Plant
- Sere
- Continental
What is a sere?
An ecological succession which sequesters carbon oer time