Water EQ2 - Variations in the hydrological cycle

Question 1

What are the four types of drought?

Answer 1

Meteorological, hydrological, agricultural, famine

Question 2

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

Answer 2

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

Question 3

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

Answer 3

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

Question 4

What is agricultural drought and what are its major impacts?

Answer 4

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

Question 5

What is famine drought and what are its major impacts?

Answer 5

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

Question 6

Why are droughts known as creeping hazards?

Answer 6

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)

Question 7

How does the Crop Moisture Index measure drought?

Answer 7

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

Question 8

What happens during an El Nino year?

Answer 8

• trade winds weaken, water sloshes towards south america
• low air pressure in south america, rises and cools leading to intense rain events
• high air pressure in south east asia/australia lead to drought and wild fires
• becoming more intense due to climate change

Question 9

What happens during a La Nina event?

Answer 9

This is an exaggerated version of a normal year
- trade winds become more strong
- warm water is pushed west, leading to heavy rain/cyclones in southeast Asia due to low pressure conditions
- high pressure develops in south america, leading to drought

Question 10

What is desertification?

Answer 10

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

Question 11

Do human factors cause drought?

Answer 11

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

Question 12

What are the human and physical causes of desertification?

Answer 12

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

Question 13

What is a wetland?

Answer 13

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

Question 14

What are the key functions of wetlands?

Answer 14

• 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

Question 15

What are the ecosystems services of wetlands?

Answer 15

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

Question 16

Why has there been wetland habitat loss?

Answer 16

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

Question 17

What is flooding?

Answer 17

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

Question 18

What is groundwater flooding?

Answer 18

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

Question 19

What is surface water flooding?

Answer 19

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

Question 20

What is flash flooding?

Answer 20

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

Question 21

What are the physical causes of flooding?

Answer 21

• 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

Question 22

What are the human actions exacerbating flood risk?

Answer 22

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

Question 23

What are the socio economic impacts of flooding?

Answer 23

• 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

Question 24

What are the environmental impacts of flooding?

Answer 24

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

Question 25

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

Answer 25

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

Question 26

Why is modelling climate change trends complex?

Answer 26

- 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

Question 27

How can climate warming modify the hydrological cycle?

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

- loss of snow and glaciers as cryosphere stores - depleted aquifers - change in wetland capacity - increased evaporation from oceans

Question 30

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

Answer 30

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

Question 31

How has flooding changed with climate change?

Answer 31

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

Question 32

How have droughts changed with climate change?

Answer 32

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

Question 33

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

Answer 33

- 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

Question 34

australian drought 2019

Answer 34

-hottest and driest year in australia ever recorded due to el nino conditions -crop failues, livestock deaths, water insecurity -commodity prices increased- farmers struggling -cost economy over $100b AUD- provided millions in drought relief -farmers adopted drought resistant crops

Question 35

storm eva

Answer 35

4,000+ homes flooded (notably in Leeds, York, and Greater Manchester) Disruption to Christmas holidays, evacuations, and stress for residents 1.3 bil in damages destroying of businesses reasons Urbanisation: High percentage of impermeable surfaces in towns (e.g., Leeds) increased surface runoff. River Management Failures: Some flood defenses (e.g. in Mytholmroyd) were overwhelmed or breached. already saturated ground after storm desmond The jet stream was unusually strong and positioned directly over the UK. It steered low-pressure systems like Storm Eva and Storm Desmond toward the UK. This led to persistent frontal rainfall flood defences were improved after

Question 36

sahel region

Answer 36

-1.5 degrees temperature increase since 1970s -40% decrease in rainfall -increased desertification -increased food insecurity

Question 37

drought resistant crops in the sahel region

Answer 37

Some farmers increased yields by up to 30% even during dry seasons. Helped reduce migration from rural to urban areas. Boosted household incomes and reduced reliance on food aid. however seeds can be expensive

Question 38

how can ITCZ movement cause drought

Answer 38

inter-tropical convergence zone The ITCZ shifts north in the Northern Hemisphere summer and south in the Southern Hemisphere summer, Regions depend on this movement to bring their wet season like the sahel. the the ITCZ doesn't move far enough, this leads to drought conditions in the sahel and water insecurity. climate change can lead to erratic movement and can change el nino and la nina which interact

Question 39

palmers drought severity index

Answer 39

It helps measure how severe a drought is by looking at how much water is in the soil. australia - -3 /-4 severe, extreme drought