Water EQ2 - Variations in the hydrological cycle Flashcards

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1
Q

What are the four types of drought?

A

Meteorological, hydrological, agricultural, famine

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2
Q

What is meteorological drought and what are it’s main impacts?

A

Shortfalls in precipitation as a result of short term variability within the longer term average overall.
MAJOR IMPACTS - loss of soil moisture, supply of irrigation water declines

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3
Q

What is hydrological drought and what are it’s main impacts?

A

Associated with reduced stream flow and groundwater levels, which decrease because of reduced precipitation inputs and continued high evaporation rates
MAJOR IMPACTS - reduced storage in lakes and reservoirs, poorer water quality

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4
Q

What is agricultural drought and what are its major impacts?

A

The rainfall deficiency from meteorological drought leads to deficiency of soil moisture and soil water availability which reduces biomass
MAJOR IMPACTS - poor crop yields, failure of irrigation systems, rural industries affected

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5
Q

What is famine drought and what are its major impacts?

A

A humanitarian crisis in which the widespread failure of agricultural systems leads to food shortages and famines with severe social, economic and environmental impacts
MAJOR IMPACTS - rural to urban migration as rural economy collapses, aid required, increased malnutrition

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6
Q

Why are droughts known as creeping hazards?

A

They typically have a long period of onset, sometimes several years (it is difficult to determine whether it is a drought or dry period initially)

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7
Q

What are some of the measurements of drought?

A
  • Palmer Drought severity index
  • Crop moisture Index
  • Palmer Hydrological drought index
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8
Q

How does the Palmer Drought Severity Index measure drought?

A

Focuses on monitoring duration and intensity of large scale, long term drought inducing atmospheric circulation

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9
Q

How does the Crop Moisture Index measure drought?

A

Measures short term drought on a weekly scale, is useful for farmers to monitor water availability during the growing season

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10
Q

How does the Palmer Hydrological Drought Index measure drought?

A

Uses different models to monitor hydrological systems responses to drought - both reacting and recovering to it

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11
Q

What is El Nino?

A

El Nino refers to the increase in sea-surface temperatures that periodically develop across the east-central equatorial Pacific.

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12
Q

What happens during an El Nino year?

A
  • trade winds in western Pacific weaken and die, reversing the air circulation loop
  • this causes a reversal of the warm water which piles up in the eastern Pacific
  • conditions become calmer across the whole of the Pacific
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13
Q

What is La Nina?

A

La Nina refers to the periodic cooling of sea-surface temperatures across the east-central equatorial Pacific.

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14
Q

What happens during a La Nina event?

A

This is an exaggerated version of a normal year
- trade winds become more strong
- warm water is pushed westwards, leading to heavy rain in southeast Asia due to low pressure conditions
- high pressure develops on the Eastern pacific, leading to drought

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15
Q

What is desertification?

A

Land degradation in arid, semi-arid and dry sub-humid regions resulting from various factors including climatic variations and human activities

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16
Q

Do human factors cause drought?

A

No, but they act like a positive feedback loop in enhancing its impact

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17
Q

What are the human and physical causes of desertification?

A

HUMAN - overgrazing, overcultivation and deforestation (due to increase in animals and population)
PHYSICAL - less rainfall and global warming
These factors lead to a removal of vegetation and therefore an increase in evaporation from the soil, leading to increased risk of soil erosion

18
Q

What is a wetland?

A

A distinct ecosystem that is flooded or saturated by water, either permanently or seasonally, acting as a temporary store in the water cycle

19
Q

What are the key functions of wetlands?

A
  • temporary water stores in the hydrological cycle (recharge aquifers)
  • act like giant water filters by trapping and recycling nutrients and pollutants
  • high biological productivity by supporting very diverse food web
  • provide resources and services within water and carbon cycle
20
Q

What are the ecosystems services of wetlands?

A

Supporting - primary production, nutrient cycling, food chain, carbon cycle
Regulating - flood control, water purification
Provisioning - fuelwood, peat, fisheries
Cultural - aesthetic value, recreational use, cultural heritage

21
Q

Why has there been wetland habitat loss?

A

Agriculture and urban development
Also water transfer schemes and the exploit of fuel resources such as peat

22
Q

How can drought impact on wetlands?

A

Limited precipitation = less interception as vegetation deteriorates, transpiration decreases and wetlands become less functional. Desiccation can also accelerate destruction by wildfires.

23
Q

What is flooding?

A

Flooding occurs when discharge is of a sufficient enough quantity to cause a body of water to overflow it’s channel and submerge the surrounding land

24
Q

What is groundwater flooding?

A

Flooding that occurs when the level of water in rock or soil rises above the ground (water table rises)

25
Q

What is surface water flooding?

A

Flooding that occurs when intense rainfall has insufficient time to infiltrate the soil, so flows overland

26
Q

What is flash flooding?

A

A flood with an exceptionally short lag time, often minutes or hours

27
Q

What are the physical causes of flooding?

A
  • Prolonged and heavy rain associated with the passage of low pressure systems or depressions
  • Seasonal monsoonal rainfall in Asia
  • Tropical storms or cyclones
  • Snow/ice melt and jokulhlaups
28
Q

What are the human actions exacerbating flood risk?

A

Urbanisation is the main one - creation of impermeable surfaces, artificial conduits speeding up the drainage of water, impeding channel flow
Also changing land use associated with agricultural development - DEFORESTATION

29
Q

What are the socio economic impacts of flooding?

A
  • mortality
  • post flood morbidity due to spread of water borne diseases
  • destruction of property and infrastructure
  • livelihoods affected
  • crops, livestock and agricultural infrastructure suffer damage
  • loss of food supplies leading to famine
30
Q

What are the environmental impacts of flooding?

A

Some positives - floods play an important role in maintaining key ecosystem functions and biodiversity by linking river with land surroundings
- recharge groundwater systems
- trigger breeding, migration, dispersal
However intense flooding can lead to eutrophication, polluted waters and erosion

31
Q

What is eutrophication?

A

Excessive richness of nutrients in a lake or other body of water, leading to a dense growth of plant life and death of animals from a lack of oxygen

32
Q

What will the impact of climate change be on the hydrological cycle?

A

Most scientists agree that climate change (global warming and oscillations such as ENSO) will result in an intensification, acceleration or enhancement of the global hydrological cycle

33
Q

Why is modelling climate change trends complex?

A
  • climate dynamics: interaction of the spheres only partially understood
  • as a results of teleconnections, it is difficult to distinguish between impacts of oscillations like ENSO and climate warming
  • global records are very incomplete, making it hard to make predictions
34
Q

How can climate warming modify the hydrological cycle?

A

Surface heating → increase in evaporation (drought?) → increase in moisture content of atmosphere due to increases in temp → enhanced precip rates → enhanced latent heating and therefore storm intensity → changes in precip amount, distribution, increased flooding

35
Q

What is the impact of climate change on hydrological cycle inputs/outputs?

A
  • higher temp = more evaporation
  • decreasing rainfall in some areas of the world
  • more intense precip in many areas due to enhanced moisture holding capacity
36
Q

What is the impact of climate change on hydrological cycle stores/flows?

A
  • loss of snow and glaciers as cryosphere stores
  • depleted aquifers
  • change in wetland capacity
  • increased evaporation from oceans
37
Q

How has the moisture holding capacity of the atmosphere been changing?

A

Increasing by a rate of about 7% per degree Celsius of climate warming, therefore creating the potential for heavier precipitation

38
Q

How has flooding changed with climate change?

A

Despite hydrological cycle intensifying, documented flood figures show no clear evidence of trends in increasing freq or magnitude of flood events globally

39
Q

How have droughts changed with climate change?

A

Climate change influences precip, temp and EVT rates - and therefore occurrence and severity of droughts
In past 30 years, droughts have become more widespread, more intense and more persistent: but it is hard to disentangle impacts of climate change from human influences

40
Q

What are the impacts of short term climate change on water supply?

A
  • increase in annual temp leads to great evaporation from surface water and reservoirs
  • greater EVT rates, desiccation of forests store
  • unreliable rainfall patterns due to oscillations like ENSO
  • depleted aquifers leads to problems with groundwater
  • decreasing rainfall
  • loss of snow and glaciers
  • increased intensity and freq of droughts