EQ2 - Factors influencing the Hydrological cycle Flashcards
What is meteorological drought?
A deficiency of water over an extended period
What is hydrological drought?
Where there is reduced stream flow, lowered groundwater levels and reduced water stores
What is agricultural drought?
When soil moisture is reduced, affecting agriculture
What is a deficit (when input is less than output) in the hydrological system, better known as?
A drought
What are the 4 main characteristics of Meteorological Drought?
- Low Precipitation
- High temperatures
- Strong winds
- Increased solar radiation
What are the 3 main impacts of meteorological drought?
- Loss of soil moisture
- Less water for irrigation (agriculture)
- Less water for consumption (domestic)
What are the 3 main characteristics of hydrological drought?
- Reduced infiltration
- Low soil moisture
- Little percolation and groundwater recharge
What are the 4 main impacts of hydrological drought?
- Reduced storage in lakes/reservoirs
- Less water for urban supply
- Poor water quality
- Wetland habitats threatened
What are the 3 main characteristics of agricultural drought?
- Low evapotranspiration
- Reduced biomass
- Fall in groundwater level
What are the 5 main impacts of agricultural drought?
- Poor yields for rainfed crops
- Failing irrigation systems
- Government aid may be needed to support rural industries
What are the 4 main socio-economic impacts associated with drought?
- Food shortages (due to agriculture failure)
- Rural economy collapse
- Rural-urban migration
- Wildfires
What process can begin to occur during extended periods of drought?
Desertification
What is El Niño? (ENSO)
The slackening/reversal of trade wind patterns
Typically (in a non ENSO period) where are cool/warm waters found?
(in the pacific)
Cold water along Peruvian Coast
Typically warm water around Australia
How does the pattern of cold water (Peru) and warmer water (Australia) switch during El Niño?
Complete reversal - Australia cold, Peru Warm
How often, and for how long, do ENSO cycles typically last?
Occur every 3-7 years
Last around 18 months
The harvest of which fish in Peru is usually indicative of ENSO occurrence?
Anchovies
- They prefer cold waters
- When ENSO warms water in Peru, Anchovy harvest usually falls
How does ENSO affect areas such as South East Asia, East Australia and North-East Brazil?
Causes extremely dry conditions
In a non El Niño Year, what direction do trade winds blow?
East to West (along the equator)
What seasonal storms in India and South East Asia often fail in El Niño periods?
Monsoons
What events can sometimes (but not always) follow an El Niño event?
La Nina
Explain the La Niña process
The build-up of cooler-than-usual subsurface water in the central/eastern Pacific
What function do Wetlands serve within the Hydrological system?
Act as temporary water stores, helping to mitigate river floods
Chemically, how do Wetlands help to maintain river quality?
Act as Water Filters
- Trap and recycle nutrients and pollutants
Wetlands have a low biological productivity and support a limited food web
True or False?
False
- they support a diverse food web, home to fish and migrating birds
How does Meteorological drought impact wetlands?
Less precipitation causes vegetation to die
- affects soil nutrients
- disrupts complex food web
Define Desertification
Once-productive land gradually becomes unable to support plant/animal life
Desertification is not irreversible
True or False?
True - in some cases it can be reversed
Explain the first stage of desertification
- Less reliable rainfall, both seasonally and annually
- Drought can now sometimes extend into multi-year periods
Explain the second stage of desertification
- Vegetation death
- this leaves soil exposed and vulnerable
Explain the third stage of desertification
- Soil Erosion
- without protection from vegetation, bare soil is eroded by wind
Explain the fourth (final) stage of desertification
- Rain intensity issues
- When rain eventually does fall, it is in short bursts
- Decertified soil struggles to absorb/store the water
How much less rainfall, compared to historical averages, is the Northern Sahel currently experienced?
30-40% less rainfall than usual
Whilst the Northern Sahel is getting 30-40% less rainfall than usual, the central/southern Sahel is mostly unaffected
True or False?
False - issues are widespread
- Central Sahel 25-30% less
- Southern Sahel 20-25% less
How is population growth in vulnerable areas enhancing desertification?
Greater demand for food, water and resources places additional stress on the land
How is the intensification of cattle farming enhancing desertification/drought?
- Large areas of forest cleared for grazing land, exposing soils
- Overgrazing kills vegetation and reduced the ability for the land to recover
How is the intensification of crop farming enhancing desertification/drought?
- Time between harvests reduced to keep up with food demand
- Shorter ‘fallow’ periods prevents the soil from regenerating, reducing fertility
How is deforestation enhancing desertification/drought?
Removes the root systems that stabilises soil
- soil more vulnerable to erosion and becomes infertile
Desertification is an example of what type of feedback loop?
Positive feedback loop - initial change triggers processes that amplify impacts
In the case of the Sahel, what other human factor has contributed to desertification/land degradation?
Frequent civil war
- crops, livestock and homes have been deliberately destroyed in conflict
What % of Australia is affected by severe rainfall deficiency (drought) annually?
30% of the country
What drought event in Australia 2006 has been the most severe?
The ‘Big Dry’
The ‘Big Dry’ in 2006 is considered a 1 in 1000 year event
True or False?
True - thought to be associated with longer-term climate change
What natural process is responsible for some degree of drought in Australia?
El Niño
What 3 management methods have Australia used to avoid the desertification cycle seen in the Sahel?
- Management of scarce water resources
- Balancing irrigation and urban water demands
- Water conservation strategies
What is grey water recycling?
Using waste water from baths, sinks etc. for irrigation and industrial purposes
How is grey-water recycling effective in managing drought in Australia?
Reduces pressure on freshwater sources by reusing waste water
What is desalination, as a drought management method?
Converting seawater into freshwater
How is desalination effective in managing drought in Australia?
Reduces dependence on unreliable rain patterns
- sustainable alternative
- ensures urban areas remain water secure in times of low rainfall
What 4 water conservation strategies have been promoted in Australia?
- Public campaigns - to encourage water-saving habits
- Use of water-efficient devices (e.g low-flow shower heads)
- Rainwater harvesting systems (capture/store rainwater)
- New water-efficient farming techniques (e.g drip irrigation)
How does Australia’s governance support drought management?
Strong governmental support/funding for climate resilience measures
How does Australia’s technology support drought management?
- Weather monitoring tech for early warnings/prediction
- Lots of R&D in sustainable water use
What are the 3 keys differences in water management approaches in Australia vs the Sahel?
- Australia can afford technology (e.g desalination)
- Australian people more educated on water conservation
- Australia has a stable government which funds drought mitigation
What % of the earth’s land surface is covered by Wetlands?
10%
What are surpluses within the Hydrological cycle more often known as?
Floods
What are the 3 meteorological causes of flooding?
1.Intense short storms (flash flooding)
- Prolonged heavy rain (Monsoon)
- Rapid snowmelt
What is the flood-prone country with major rivers including the Ganges, Padma and Meghan?
Bangladesh
What 2 meteorological process cause rivers in Bangladesh (e.g the Ganges) to swell twice a year?
- Meltwater from the Himalayas
- Summer Monsoon
What area in Bangladesh is most vulnerable to flash floods?
The hilly areas of Chittagong, located between the major rivers
Define ‘Tidal flooding’
The temporary submergence of land areas due to the rise/fall of tides
When does Tidal flooding most commonly occur?
When high spring tides combine with storm surges
What causes a ‘storm surge’?
Very low air pressure
Why are ‘storm surges’ often the cause of tidal flooding?
Low air pressure raises the height of the sea - coastal defences become ineffective
How does low lying land with impervious surfaces increase the likelihood of flooding?
As water cannot infiltrate the ground
- more surface run-off which overwhelms drainage systems
How does ground underlain by impermeable rocks increase the likelihood of flooding?
Water cannot seep into soil
- more surface run off, water cannot be drained
How does the sudden melting of ice dams and release of waters in glacial lakes increase the likelihood of flooding?
Water trapped behind ice dams is rapidly released
- sudden release overwhelms the natural flow of rivers
- causes flooding downstream
How does volcanic activity generating meltwater (jokulhlaups) increase the likelihood of flooding?
Sudden surge of meltwater (jokulhlaups) causes flash floods
- especially in areas of weak infrastructure
How does an earthquake increase the likelihood of flooding?
Cause dams to collapse or landslides to block rivers
What are 3 examples of river mismanagement?
- Channelisation
- Dams
- River embankments
Why is channelisation an ineffective management strategy?
It simply displaces the river - downstream locations may be overwhelmed by increased discharge
Why are dams an ineffective management strategy?
Block the flow of sediment downstream
- this leads to increased riverbed erosion (more vulnerable to flooding)
Why are river enbankments an ineffective management strategy?
They can fail if floods are of a certain magnitude
- when this happens, the scale of flooding is much greater
What is the best example of soft-engineering method to reduce flood risk?
Leaving floodplains as natural buffers (land-use zoning)
- floodplains reserved for recreational and agricultural activity, rather than large-scale development
What are 3 most common causes of death and injury due to flooding?
- Drowning
- Collapsing buildings
- Debris
- During UK 2007 there were several deaths directly attributed to the floods
How is the spread of water-borne diseases a socio-economic impact of flooding?
Can lead to breakouts such as cholera in extreme cases
- more common in developing countries
How is Trauma a socio-economic impact of flooding?
Victims can experience psychological issues (e.g PTSD) due to the sudden loss of homes and livelihoods associated with flooding
How many homes and businesses were impacted in the 2007 UK floods?
Over 48,000
During the UK floods in 2007, what was the name of the Water Treatment works which became submerged, cutting over drinking water for 140k people?
Mythe Water Treatment, Gloucester
List some socio-economic impacts of flooding
- Death and injury
- Water borne diseases
- Trauma
- Damage to property
- Transport and communication disruption
- Water and energy disruption
- Crop destruction
- Disruption to work
Why do the environmental impacts of flooding receive much less publicity?
There are some positives of flooding for the environment
What are 3 positive impacts of flooding for the environment?
- Recharged groundwater stores
- Soil replenishment
- more connectivity between aquatic habitats
What is ecological resilience, in relation to flooding?
An ecosystems ability to withstand and recover from moderate flooding
What fundamentally reduces ecological resilience?
Human activities make the impacts of flooding harder for ecosystems to cope with
- e.g deforestation, soil degradation
Define eutrophication
Process by which a water body becomes excessively enriched with nutrients (e.g nitrogen and phosphorous)
- this causes algal blooms that deplete oxygen and harm aquatic life
How can flooding contribute to eutrophication in water bodies?
Floodwaters remove soil and sediment, which carry nutrients into water bodies (eutrophication)
What effect can pollutants carried by floodwaters have on ecosystems?
Can poison aquatic life, disrupt ecosystems, and contaminate drinking water
How can diseases carried by floodwater impact trees and wildlife?
They infect and weaken/kill trees and wildlife
- this reduces biodiversity and disrupts ecological balance
What year was some of the UKs most recent severe floods?
2007 and 2016
During the 2016 floods how much more rainfall did some areas receive?
2x
- Carlisle and Cockermouth were two of the worst-hit places
During the UK floods, what was blamed for the ineffectiveness of flood protection.
- Budget cuts on flood defences
- EU conservation put environmental conservation ahead of dredging of rivers
- Poor land-use management
- Global warming
What is often overlooked in post-flood enquiries
Flood-protection is designed to handle events of a specific magnitude.
- rare, extreme events can exceed these limits, regardless of how much is spent
Why can even the best flood protection measures fail during extreme events?
No amount of money/engineering can fully protect against very rare, extreme flood cases
- those that surpass the capacity of flood protection systems
Define ‘Anthropogenic Global Warming’
Warming due to increased greenhouse gases in the atmosphere
If global warming continues, and land and sea temperatures continue to rise, how may ENSO cycles be affected?
The period between ENSO cycles (currently 2-3 years) will decrease
What 2 possibilities may occur in different parts of the world if global temperatures rise?
- increased evaporation (output) - causing drought
or
- more convectional rainfall - causing intense tropical cyclones and flooding
Climate Change will increase outputs, increase stores but may decrease outputs
True or False?
False - outputs likely to increase
What 2 examples of depleted stores may occur with climate change?
- Reduced snow/glacial mass
- Reduced capacity of groundwater store (water table drops)
What 2 unpredictable factors mean that managing future change to the hydrological cycle is almost impossible?
- Climate Change
- ENSO cycles
