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Geography Topic 5 - Water > EQ2 - What Factors Influence The Hydrological System Over Short And Long Term Timescales > Flashcards

EQ2 - What Factors Influence The Hydrological System Over Short And Long Term Timescales Flashcards

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1
Q

Define Drought

A

An extended period of deficient rainfall relative to how much precipitation a region would expect.

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2
Q

Define water deficit

A

When water demand exceeds supply

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3
Q

What are the 4 types of drought

Rank them least to most serious

A 
Meteorological drought (Rainfall deficit)
Hydrological drought (Stream flow deficit)
Agricultural drought (Soil moisture deficit)
Famine drought (Food deficit)
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4
Q

What happens during a meteorological drought

A

Low precipitation
High temperatures
Loss of soil moisture
Increased evapotranspiration

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5
Q

What happens during a hydrological drought

A

Reduced infiltration
Reduced storage in lakes and reservoirs
Low soil moisture
Poorer water quality

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6
Q

What is agricultural drought

A

Low evapotranspiration
Reduced biomass
Livestock productivity declines
Some government aid required

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7
Q

What is famine drought

A

Loss of natural vegetation
Food shortages on a seasonal scale
Increased malnutrition and mortality
International aid required

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8
Q

Explain how global atmospheric circulation is a physical cause of drought

A

At the ITCZ there is low pressure
In the subtropics there is a high pressure zone with hot and dry conditions due to cool air sinking
At the poles warm air rises, cools and sinks to create high pressure and a lack of precipitation
The cells which transfer heat means the subtropics and poles receive no precipitation, causing drought

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9
Q

Explain how the failing of the ITCZ is a physical factor which can cause drought

A

The ITCZ is a belt of low atmospheric pressure which moves north and south of the equator seasonally
The ITCZ causes an alternating wet season when it arrives and a dry season when it moves away.
Some subtropical high pressure zones block the high humidity rain masses of the ITCZ , causing a lack of precipitation and drought

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10
Q

Explain how blocking high pressures are a physical cause of drought

A

Frontal precipitation is created in low pressure along the polar front which moves west to east due to the Coriolis force
The low pressure stream occasionally stabilises, allowing high pressure areas to move in and block low pressure areas, leading to very little precipitation causing drought

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11
Q

What is the ENSO

A

El Nino Southern Oscillation

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12
Q

Describe how a normal year in the Pacific ocean works

A

Trade winds blow warm water eastwards
There is an upwelling of cold water in the eastern pacific
There are lower temperatures in the east and higher temperatures in the west

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13
Q

Describe the effect of an El Niño year in the pacific

A

Trade winds in the east weaken and die, it the moves west into the middle of the ocean
The west has flooding due lower pressure, rising and cooling of warm air
The east has drought due to high pressure, from colder water rising and sinking

An el Nino occurs approximately every 2-7 years

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14
Q

Describe the effect of a La Niña year in the pacific

A

There are extremely strong trade winds which push warm water east
In the east low pressure develops with thick clouds, heavy rainfall and flooding due to warm air rising and cooling
In the west there is drought due to high pressure from cold air sinking

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15
Q

What is the Sahel region (area of drought)

A

The sahal region is in the tropic of cancer in a high pressure zone

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16
Q

What is the are examples of human factors which caused drought in the Sahel

A

Human factors are socio-economic conditions due to overgrazing , deforestation for fuelwood and high levels of poverty.
Population outstripped food production
Agriculture was rain fed making it vulnerable to drought

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17
Q

What is the impact of human factors on causes of drought

A

Human factors do not cause droughts but they act like a positive feedback loop in enhancing its impacts.

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18
Q

Define Resilience

A

Is the capacity of an ecosystem to drought. Its the ecosystems ability to persist in its state despite having a water deficit

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19
Q

Define a wetland

A

An area of marsh with water permanent or seasonally

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20
Q

What is the value of the wetlands in florida

A

Habitats for plants and animals
Absorbs excess water which helps control flooding
Control erosion as plants anchor soil
Helps absorb storm surges
Natural water purification system
Provides us with food and recreational activites

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21
Q

Describe wetlands resilience

A

Are not resilient to drought due to their reliance on the submergence of water for a long period of time

22
Q

What impacts does Drought have on Wetlands in Florida

A

Limited precipitation means less interception
Less infiltration, percolation and groundwater storage causing the water table to fall
High rates pf evaporation
Low rates of transpiration making wetlands less functional

23
Q

What is the value of forests in california

A

Goods such as timber, food, fuel and bio products
Ecological functions like carbon storage , nutrient cycling, water and air purification and maintenance of wildlife habitats
Social and cultural benefits like recreation and spiritually

24
Q

What are the reasons for drought and wildfires in the california forests

A

Wildfires have been getting worse in terms of power and size
Drier and warm conditions lead to vegetation drying out and becoming more flammable
Drying out of soil and lowering of the water table reduces the natural protection
Winter seasons where precipitation occurs is getting shorter

25
Q

What are the 3 meteorological causes of floods

Give and example of where

A

Jet stream and low pressure weather - UK

Monsoon - India

Ice melt - Siberia

26
Q

Explain how the jet stream and low pressure weather causes flooding

A

The jet stream is a ribbon pf very strong winds that moves weather systems
Drastic temperature differences between the cold artic air and the warm tropical air causes a stronger jet stream
Brings low pressure cyclonic rainfall formed by the warm and cold front meeting , causes high rainfall and flooding

27
Q

Explain how the Monsoon causes flooding in India

A

A monsoon climate is a dramatic seasonal change in the direction of prevailing winds
A dry season is followed by a wet season due to low pressure systems from the Indian Ocean.
Convectional rainfall is caused by the rising of warm air, cyclonic rainfall then occurs as the warm and cold front meet and orographic rainfall occurs due to the cold front rising at the Himalayas.
There is extremely high rainfall and flooding

28
Q

Explain how Ice melt in Siberia causes flooding

A

Snowmelt occurs causing meltwater, increasing the river discharge and causing flooding, happens in summer
In winter river level returns to normal and the gulf begins to shortly refreeze.

29
Q

Explain how the position of the jet stream (warm conveyor belt) caused flooding in Cumbria in 2015

A

A jet stream was tracked from the Caribbean and built up due to unusually high sea temperatures
Brings Laden depressions of heavy rainfall to Cumbria
Storm Desmond was an atmospheric river

30
Q

Explain how the low pressure system caused flooding in Cumbria in 2015

A

The low pressure system is developed from the jet stream where strong troughs of low pressure are formed
The LP system builds up and cyclones of heavy rainfall and strong winds were brought to Cumbria on the west coast.

31
Q

Explain how Orographic rainfall caused flooding in Cumbria in 2015

A

Rainfall which forms due to air having to rise over mountainous regions
Hot humid air from the ocean reaches the mountains in Cumbria, the air rises and cools causing clouds to form and heavy rainfall occurs

32
Q

Explain how antecedent conditions and rainfall intensity causes flooding in Cumbria in 2015

A

Past rainfall in November ,where rainfall was high, meant the ground was fully saturated, surface run off occurred causing flooding
High amounts of precipitation fell in a short amount of time , the intensity was too high

33
Q

Explain how geology caused flooding in Cumbria in 2015

A

The steep slopes of cumbria increased the flow of surface run off into the river
The river eden is a drainage basin for the Lake District and Pennies which are impermeable , high amounts of discharge
Cockermouth is built on the confluence of two rivers meaning its susceptible to flooding

34
Q

How is population growth a human cause of flooding in Cumbria 2015

A

An increased population means floodplains are built on, areas are susceptible to flooding
Increased population causes increased food demand. More agriculture is needed, leading to increased ploughing and grazing, increased surface run off
Increased population leads to increased water demand. Dams are built , increasing river flow downstream.

35
Q

Explain how urbanisation is a human cause of flooding in Cumbria 2015

A

Gardens are being replaced by impermeable concrete (In London this is 22x the size of Hyde Park) . Leads to increased surface run off and pressure on the drainage basin
Speeding up the drainage of water through sewers and drains leads to increased flow
Urbanisation in Carlisle leads to increased surface run off

36
Q

Explain how Land Use Changes cause flooding in Cumbria

A

Causes Deforestation which leads to increased levels of surface run off and river discharge
Draining wetlands increases run off and increases levels of sediment (block drainage basin)

37
Q

Explain how Poor river management was a human cause of flooding in Cumbria

A

Straightening channels increases the river flow and causes flooding downstream
There was no dredging of the gravel which raised the river level considerably.

38
Q

Explain how Economics and Politics was a human cause of flooding in Cumbria

A

Budget cuts in the amount of money spent on flood defences
Flood defences were designed for a 1 in a 100 year event , overtopped easily
The drains and sewers were inadequate for the high levels of rainwater

39
Q

What impact does climate change have on inputs in the hydrological cycle locally and globally
(What type of input)

A

Precipitation input : causes increase in drought occurrence and decreased frequency and length of rainfall

Snow : Snow cover has decreased and spring melt has occurred earlier

40
Q

What impact does climate change have on the flows in the hydrological cycle locally and globally
(Name the flows)

A

Run off and stream flow : intense rainfall increases surface run off and decreases percolation.

Groundwater flow : No definitive link between groundwater amounts and climate change, influenced by human activities.

41
Q

What impact does climate change have on stores in the global hydrological cycle
(Name the store)

A

Soil moisture : where precipitation increases soil moisture will also increase

Reservoir, lake and wetland storage : decreases water volumes and higher temperatures

Permafrost : causes permafrost degradation, deepening of the active layer, methane released in thawing lakes and positive feedback.

Ice : glaciers have retreated due to temperature increases and changes in precipitation type

Oceans : ocean warming causes increased evaporation

42
Q

What impact does climate change have on the outputs in the global hydrological cycle
(Name the outputs)

A

Evapotranspiration : increased cloud cover (from water vapour) effects evaporation. Increased transpiration makes vegetation more productive

43
Q

What impact does climate change in the Sahel have on inputs into the hydrological cycle

A

If the tropical regions warm up the ITCZ will not migrate as far north, causing rain bearing masses to fail

Climate change makes the precipitation less predictable and causes long periods of drought

44
Q

What impact does climate change have on stores and flows in the Sahel

A

A lack of precipitation is leading to : declining reservoirs, lack of surface run off and low soil moisture levels

45
Q

Explain the process of regreening in the Sahel

What are the benefits of it

A

Is the conversion of dry landscapes to productive farmland
Several wet years in the Sahel has provided the opportunity for regreening

Its benefits include:
Natural regeneration of water holding shrubs and trees
Low cost of reforesting
Use of water harvesting for farmers

46
Q

What are the uncertainties over the projections of climate change and its effect in the Sahel

A

One possible future projection is that climate change will lead to warmer tropics, causing low rainfall and a dry Sahel

Another possible projection is that climate change will lead to warmer polar areas, leading to higher rainfall and a wetter Sahel

47
Q

What are the possible effects of climate change in California

A

There have been projections of mega droughts
Rising temperatures will lead to increased evaporation rates and less stored water
There will be a fall in precipitation

48
Q

What is the evidence of climate change in California

A

Surface run off and soil moisture levels have declined
Forested areas have become dry grasslands
Groundwater levels have declined
Reservoir levels have declined
Permafrost levels have declined due to higher temperatures

49
Q

What is the effect of climate change on flooding and droughts

A

More varied precipitation, temperature and evapotranspiration will cause the occurrence and severity of droughts and floods
to increase

More intense droughts and floods will effect more areas have a wider effect on the world

50
Q

What are the sources of uncertainty with climate change projections

A

The complexity of climate systems
Natural short term oscillations (ENSO)
Incomplete projection data

Geography Topic 5 - Water (3 decks)

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