Topic 5 - Water EQ2 Flashcards
1
Q
Explain briefly what a drought is ?
A
Droughts exist when there is a water deficit in a particular place over a period of time, compared to the average rainfall for that same period - 3 main types
- described has having a slow onset, as they develop gradually
2
Q
What are the three types for droughts?
A
- agricultural
- hydrological
- meteorological
3
Q
What are meteorological droughts, what’s are the 5 features?
A
Caused by a rainfall deficit - features include:
- low precipitation
- high temperatures
- strong winds
- increased solar radiation
- reduced snow cover
4
Q
What are the impacts of meteorological droughts - give 3?
A
-loss of soil moisture
- irrigation supply drops
- reduction in water available for consumption
5
Q
What are hydrological droughts, what’s are the 5 features?
A
Caused by stream flow deficit - features include:
- reduced infiltration
- low soil moisture
- little percolation and groundwater recharge
6
Q
What are the impacts of hydrological droughts - give 3?
A
- reduced storage in lakes and resevoirs
- less water for urban supply
- threats to wetlands and habitats
7
Q
What are agricultural droughts, what’s are the 3 features?
A
Caused by soil moisture deficit - features include:
- low evapotranspiration
- reduced biomass
- fall in groundwater level
8
Q
What are the impacts of agricultural droughts - give 4?
A
- poor yield from rainfed crops
- failing irrigation systems
- rural industries affect
- government aid may be required
9
Q
What are socio-economic droughts, what’s are the 4 features?
A
Caused by a food deficit - features include:
- loss of vegetation
- increased risk of wildfires
- soil erosion
- desertification
10
Q
What are the impacts of socio-economic droughts - give 4?
A
- rural economy collapses
- rural to urban migration
- international aid required
- humanitarian crisis
11
Q
Give the full definition of a drought
A
A drought is an extended period (season, year, several years) of deficient rainfall relative to the statistical multi year average for a region
12
Q
Briefly explain the global atmospheric circulation - include steps 1,2 and 3?
A
1) intense solar radiation at the equator (ITCZ) warms air - air rises,cools and forms clouds and rain
2) subtropical high-pressure zone is created where air that had risen at the equator cools and sinks
3)air returns to ground at the equator, creating trade winds (caused by Coriolis effect)
13
Q
Briefly explain the global atmospheric circulation - include steps 4,5 and 6?
A
4) trade winds meet at the intertropical convergence zone where warm air rises - position of ITCZ moves with the seasons
5)warm air moving from the subtropics to mid-lattitudes meets cold polar air - warm less dense air rises, causing rainfall
6)warmer air rises into polar front jet stream - transferred to poles where it cools,sinks and moves back to the equator
14
Q
Explain what the intertropical convergence zone (ITCZ) is?
A
A belt of low atmospheric pressure located around the equator (moves north or south seasonally) - evaporation form oceans and air rising at the ITCZ due to heating from sun causes an alternating wet season (when it arrives) and dry season (when it moves away) in some world regions
15
Q
Explain why the ITCZ alternates seasonally?
A
Moves north of south of the equator seasonally - for example its further north during the northern hemisphere summer
16
Q
Explain how the ITCZ can be modified?
A
Subtropical high-pressure zones (associated with descending convection cells, Hadley cells) block the high humidity, rain-bearing air masses associated with the ITCZ modifying the pattern
17
Q
Explain how a severe drought could occur in Sahel?
A
Over continental areas such as Africa there may be lower humidity levels because less water evaporates, if high pressure zones block the arrival of the wet season, a severe drought can occur
18
Q
Explain what occurs during low pressure (depression) and any weather associated with it?
A
air rises cools and the water vapour condenses to form clouds and possibly precipitation - weather is often unsettled with various weather fronts associated with depression
19
Q
Explain what occurs during high pressure (anticyclone) and any weather associated with it?
A
air is descending, which reduces the formation of clouds and leads to light winds and settled weather conditions
20
Q
Give 3 physical causes of droughts?
A
- global atmospheric circulation
- ITCZ being blocked by high pressure
- mid latitude blocking anticyclones (high pressure)
21
Q
Explain what happens in an anticyclone?
A
Large-scale circulation of high pressure - the centre has very high pressure which makes it heavier causing the air to sink to the surface and become drier - when its at the surface it moves away from the centre in a clockwise rotation in the NH and counterclockwise in the SH
- dry and fair weather
22
Q
What weather conditions come with anticyclones?
A
Anticyclones typically result in stable,fine weather,with clear skies
- little precipitation
23
Q
Explain the main difference between cyclones and anticyclones?
A
- Cyclones are areas of low pressure where the air moves counterclockwise in the Northern Hemisphere, and clockwise in the Southern Hemisphere
- An anticyclone is associated with high pressure and its winds move clockwise in the Northern Hemisphere, and counterclockwise in the Southern Hemisphere.
24
Q
Explain how droughts are caused in mid-latitude countries referencing anticyclones and depressions?
A
Depressions move from west to east in the mad-latitudes due to coriolis effect, their path is directed by the polar front jet stream - the loops of the jet stream occasionally break up, allowing anticyclones from the subtropics to move northwards bringing with them low precipitation and heat waves
- rain bearing depressions are forced around them - usually to north but occasionally south - causing droughts in mid latitude counties (eg UK)
25
Explain why anticyclones are able to block weather systems for relatively long periods?
The stability of anticyclones with their sinking air and calm conditions means they can persist and block weather system from the west for up to two weeks
- if the situation is repeated over the space of a few months normal precipitation levels are greatly reduced and may lead to droughts
26
Give an example of blocking anticyclones disruption mid-latitude regions?
Met office reported that from 2010 to 2012 much of central,eastern and southern England and Wales expirenced a prolonged period of below-average rainfall due to blocking anticyclones
27
Explain what the El Niño-southern oscillations is (ENSO)?
The ENSO cycle is the movement of warm water mass in the equatorial Pacific Ocean, it occurs due to the changes in the trade winds,atmospheric circulation and ocean currents
- there are two phases: El Niño and La Niña
28
Explain what El Niño is, what are the conditions?
Warming of sea surface temperatures with occurs every 2-7 years (concentrated in the central-east equatorial pacific) peak is usually December
- El Niño is declared when sea temperate in the tropical eastern pacific rise 0.5 degrees above the long term average leading to warmer weather in that region
29
What does El Niño result in, give the expected weather?
The warmer waters can cause the pacific jet stream to move south from its neutral position resulting in dryer and warmer than usual conditions in northern Us and Canada
- the warmer water results in more precipitation
30
Explain El Niños effect on the western pacific?
El Niño reduces evaporation in the western pacific as water is cooler- so the affected countries experience droughts, for example Australia and Indonesia
31
Causes of El Niño - give 2?
- In a non-El Niño year there is descending air over eastern pacific and rising warm moist air over the western pacific
- in an El Niño year the trade winds are reduced or reverse (going west to east) leading to a reversal of the conditions and rising air over the eastern pacific and descending over the western pacific
32
What is La Niña?
Occurs when sea temperatures fall below average which brings cooler and drier than average weather in the eastern pacific
- occurs every 3-5 years
33
Explain a cause of La Niña?
Stronger than usual eastward trade winds and ocean currents which bring cold water to the surface through upwelling
34
Explain the conditions and what occurs in the normal ENSO cycle, reference regions and weather experienced?
Trade winds move warm surface water from east to west (resulting in precipitation around the west pacific, eg Australia)
There is some upwelling of deep cold water in the east pacific (reducing evaporation and resulting in little precipitation and droughts, in South America)
35
Explain the conditions and what occurs in the El Niño phase, reference regions and weather experienced?
Trade winds reverse direction and move warm surface water from west to east towards South America (resulting in warm rising air and precipitation around the east pacific, eg South America)
There is some upwelling of deep cold water in the west pacific (reducing evaporation and resulting in little precipitation and droughts, Australia)
36
Explain the 3 main impacts of El Niño?
- increased rainfall and flooding in South America,Africa and the south of the US
- droughts in Australia and Southeast Asia
- higher is of colder winters in the UK
37
Explain teh 3 things La Niña leads to?
- increased rainfall in Australia and Southeast Asia
- drought conditions in the south of the US
- increases the risk of tropical storms in the Alantic
38
Explain an exmaple of La Niña affecting global weather conditions?
The severe East African drought of 2011 was attributed to a strong La Niña
39
Explain how humans may have indirectly affected the development of droughts, explain actions which have caused this?
Research suggest humans have indirectly affected the development of droughts by changing land uses and altering hydrological processes - for example deforestation and overgrazing reduces vegetation cover and evapotranspiration rates thereby reducing precipitation
40
Explain how humans changing land uses may have directly affected the development of droughts, explain actions which have caused this?
Research suggests abstraction of water from rivers and groundwater and by reducing the downstream supply of water by building reservoirs and water transfer has directly affected the development of droughts
41
Explain how the removal of vegetation may lead to changes or cause droughts?
The removal of vegetation also changes soil conditions through compaction and reduced organic matter and moisture retention (soil cants store as much water) - reduces infiltration and increases surface runoff (less water storage)
42
Define resilience in regard to droughts?
is the capacity of an ecosystem to drought. It is the ecosystem’s ability to persist in its present state despite having a deficit of water.
43
Explain what the Sahel is - case study?
The Sahel is a vast semi-arid region across Africa at the southern edge of the Sahara desert it occasionally experiences severe droughts
- has been a decline in annual rainfall since 1960s
44
Explain a possible cause of the decreased precipitation in the Sahel region, referencing disruption to ITCZ - case study?
A 2002 study suggested that the Sahel droughts were caused by air pollution (sulphur-based aerosols) generated in Europe and North America which cause atmospheric cooling changing the global heat budget and atmospheric circulation - so the rain associated with the ITCZ did not arrive
45
Explain another possible cause of the decreased precipitation in the Sahel region, referencing winds failing - case study?
Study suggested that the Sahel drought could be the result of high sea-surface temperatures caused by climate warming - the rain-bearing winds that move over the Sahel appear to fail when the sea-surface temperatures in the tropical Atlantic Ocean are warmer then average
46
Explain why the Sahel region is suffering, mention both human and physical factors - case study?
The region is experiencing some of the highest population growth rates in the world which has increased demand for food and fuel (wood) this results in more deforestation and conversion of land into farmland which is being overly used and overgrazed causing desertification (fertile areas become arid, loss of vegetation)
47
Explain a problem with desertification causing droughts in the Sahel region - case study?
Reduced vegetation cover and soil moisture - means the water holding capacity of soil is minimised and the water infiltration rate is reduced - less water in the ground
- exact relationship between drought and desertification remains unclear - desertification increases human vunerability to the drought hazard
48
Explain a possible solution to the Sahel droughts, give a benefit - case study?
Re-greening - which is a technique that involves planting trees and bushes alongside other sustainable land management schemes, benefits include - natural regeneration of water retaining shrubs and trees and low cost reforesting
49
Explain the impacts of drought on ecosystems?
Ecosystems are important for human well-being as they provide us with important and invaluable services such as clean air,water,food and fuel as well as physiological benefits such as aesthetic
50
Define ecosystem functioning?
Refers to the biological,chemical and physical processes that take place within the ecosystem - all ecosystem components and processes are dependent on supplies of water
- ecosystems are vulnerable to drought (desert and semi-arid ecosystems are most resilient)
51
Explain what wetlands are?
Land saturated with water, either permanently of seasonally - they include marshes,swamps bogs and fens, they cover 6% of the earth surface
- the Everglades in Florida are an example of a large wetlands
52
Give two main ways human activities increase the risk of drought - explain why this happens?
- over-abstraction of surface water resources
- over-abstraction of groundwater aquifers
Overabstration occurs due to population grow (increasing demand for food and water) and over cultivation (over use of farmland)
53
Explain why wetlands are important for water control and prevention of flooding mention the role of both soil and plants?
Wetland soil absorbs excess water from rainfall,snow melt and agricultural runoff - it releases it slowly back into the waterways controlling flooding in the surrounding areas
- wetland plant species also slow the flow of water in channels (preventing flooding downstream) and erosion as the roots anchor the soil
54
Explain the significance of coastal wetlands in preventing flooding?
Coastal wetlands are important buffer zones which reduce tidal erosion and help absorb storm surges, reducing flooding caused by cyclones
55
Why are wetlands important for proving water?
Wetland ecosystems function as natural water purification systems - their plant species absorb excess nitrogen and other pollutants, preventing them from entering the waterways
56
Explain the economical importance of wetlands for humans?
their economic value has only recently been fully understood - Wetland ecosystems are the breeding grounds for many of the aquatic animals that provide us with food. In addition, several food plant species are dependent
on wetlands
- also provide recreational activities
57
Explain the effects of droughts on wetlands?
With limited precipitation vegetation will deteriorate so there will be less interception and less infiltration and percolation into groundwater storms (water table falls)
- evaporation continues and may increase due to less-protected surfaces
58
Explain human causes to wetland loss - give 3 examples?
- agriculture - 2.5 million square km destroyed for large agriculture and urban development - eg Florida
- water transfer schemes - eg Jonglei canal project which diverted the white Nile away from sudd swamp
- exploring fuel resources like peat
59
Explain how resilient wetlands are to droughts?
Wetlands are not resilient to droughts owing to their reliance on their submergence of water for prolonged periods of time.
60
Explain the importance of forest ecosystems - 2 examples?
- goods such as timbers,food,fuel and bio products
- geological functions such as carbon storage,water and air purification and maintenance of wildlife habitats
61
Explain the effects of droughts on forests - give 3 points?
- younger tress die reducing tree cover
- transpiration is reduced, decreasing precipitation - leading to more trees dying
- long term damage to tress - particularly the vascular tissues which affects water transport
62
Explain what happens when forests becomes less resilient?
- trees become more susceptible to pests and disease
- wildfire is more common as dry vegetation and litter covers the forest floor
63
Explain the effect of climate change on forest fires - explain in depth?
Many experts point out that climate change has made things worse, leading to higher
temperatures, lower humidity and changes in wind and rainfall patterns - this is why 9 out of 10 biggest fires have taken place in the past two decades in California
- dryer conditions means vegetation becomes more flammable and the drying of soil means the water table is lower reducing the natural protection
64
Explain the main causes of flooding in the UK?
Much of the flooding is the result of mid-latitude depressions - which bring two bands of rain, whilst in initially the ground absorbs some rainfall when through flow and groundwater flow cannot transfer the water away quick enough it becomes saturated - rain falling on saturated ground runs off into river channels increasing discharge and filling them up until they spill over onto the floods;Ian
65
Explain what a monsoon is?
Monsoon is a seasonal change in the direction of prevailing winds of a world region - involves wet and dry seasons throughout subtropical areas of the world (especially those near oceans)
66
Explain the significance of monsoons in the south East Asian region, explain why they form there?
In south east Asia and India the summer monsoon is associated with very heavy rainfall it happens when warm,moist air from the Indian Ocean blows towards India bringing a humid climate and torrential rain this is due to the ITCZ moving northwards and the warm moist air following behind
67
Explain how snowmelt leads to flooding - give an exmaple?
Flooding can arise after winter snowfall when a sudden rise in air temperature in spring causes rapid snowmelt (especially in mountain environments) results in increased surface runoff and flash floods
- Siberian snow melt in spring causes extensive flooding across inheritors of Asia
68
Explain how jet stream and low pressure weather causes flooding?
Mid-latitudes are the boundary zones between polar and tropical air masses - the jet streams is formed which brings low pressure weather (frontal rain) formed by the meeting of warm and cold air and condensation - some high pressure blocks the jet stream and continually delivers low pressure to one area as their is high pressure either side
69
Give three meteorological causes of flooding?
- snowmelt/ice melt
- monsoon
- jet stream and low pressure weather
70
Explain the human actions that increase flooding - explain land use?
Increasing population pressure which encourages vegetation removal for agricultural development and living space - these land se changes increase runoff
- mismanagement of drainage basins and floodplains also increases vulnerability
-
71
Explain the human actions that increase flooding - explain deforestation and crop growing?
Deforestation reduces interception and evapotranspiration, resulting in greater volumes and rates of surface runoff - ensures that precipitation reaches river channels faster
- Deforestation and extensive crop growing expose soil to greater rates of erosion which increases river sediment load and deposition which can reduce a rivers capacity to carry water (so more flooding)
72
Explain the human actions that increase flooding - explain urbanisation?
Urbanisation results in more impermeable surfaces which increases the rates of surface runoff into rivers via urban drainage systems (shorter lag time)
- underground channels designed to divert river water under infrastructure - often reduce river capacity
73
Explain the impact of storm Desmond on the UK - case study?
Brought severe gales and heavy rain which caused localised flooding, with Cumbria being the worst-hit county receiving more then a months rainfall in one day
- received highest discharge ever recorded
74
Explain a few features why there was so much rain with storm despond - case study?
- very low pressure
- fronts brought exceptionally prolonged and heavy rain as the air was forced. To rise across the high ground of the lake district (combination of convectional and orographic precipitation)
- existing flood defences unable to cope with the water levels
75
Explain the impacts of storm Desmond - case study?
- caused heavy rain and flooding of homes and infrastructure (5200 homes affected)
- distruption to travel (railway lines closed)
- 40 schools closed
- routine NHS appointments cancelled
76
Explain the main precipitation type involved in Storm despond, why was this the case - case study?
Orographic rainfall is common in mountainous regions (eg Lake District) - involves hot humid air from the sea reaching mountains, causing the air to rise - as it rises it cools forming clouds it then rains on the windward side of the mountain (the side which receives receives the ocean air)
- steep slopes of the Cumbria mountains meant water runoff into channels was very quick
77
Explain 3 factors which helped cause the Cumbria flooding - case study?
- rivers decent and cocker were already swollen from previous rainfall
- impermeable rock type of Lake District impeded infiltration
- cockermouth is built on the confluence of two rivers - already susceptible to flooding
78
Explain secondary human factors which contributed to the Cumbria flooding - case study?
- increase in city’s car ownership has meant more people are paving over their front gardens - an area 22 times the size of Hyde park, this has put immense pressure on drains which overflow causing the content to be discharged into rivers
- 2/3 of front gardens are completely or partially covered by paving blocks or concrete (impermeable surfaces)
79
Explain 3 other factors which increased flood risk - case study?
- deforestation - woodlands intercept rain and transpire moisture (roots give good soil structure)
- natural grasslands allow water to sink in, replaced by farmland, ploughing compacts soil
- sewers feed water into channel
80
Explain the key findings on precipitation input regarding trends in water cycle components?
- Mode may be more important than the mean precipitation in determining hydrologic impacts
- widespread increase in intense rainfall events have occurred although overall amounts remained steady of even decreased - precipitation increased in the tropics and high latitudes at the same time length,frequency and intensity of heat waves has increased widely especially in southern Europe and Africa
Precipitation mainly falling as rain not snow in northern regions
81
Explain the key findings on evaporation and evapotranspiration regarding trends in water cycle components?
In large areas of Asian and North American actual evaporation is increasing - however increased cloud cover from increased water vapour may work against this
- transpiration is linked to any vegetation changes,which are linked to any changes in soil moisture and precipitation
82
Explain the key findings on permafrost regarding trends in water cycle components?
Changes in the physical climate at high altitudes, primarily increasing air and ocean temperatures are leading to permafrost degradation in northern areas - with the deepening of the active layer this has an impact on ground water supplies and also releases methane from thaw lakes - leads to positive feedback and accelerating change
83
Explain how droughts are affecting California?
40 million Californians are facing problems due variations in the sates rainfall - Sierra Nevada region experienced three times the normal number of wildfires due to dry ground from increased evaporation rates and steep decrease in precipitation
- forecast of a 50% chance of mega-droughts hitting southwest California
84
Explain how there is already evidence of problems within the Californian regions - give 3?
- surface runoff and soil moisture levels have declined (groundwater fallen by 30m)
- forested areas have reverted to shrubs and grassland
- permanent snow levels are at record lows - crucial as its meltwater provides 1/3 of California’s water used by cities and farms
