Water EQ2 Flashcards
What is a meteorological drought
Shortfall or deficiency of water over an extended period, usually at least a season
Increased EVT, decreased precipitation
High temperature and sunshine
What are the 4 types of drought
Hydrological
Meteorological
Agricultural
Socio-economic
What is a hydrological drought
Reduced stream flow, lowered groundwater levels and reduced water stores
Water use restrictions in place as water supply decreases
What is agricultural drought
Low rainfall leads to low soil moisture
So plant growth affected, yield falls, irrigation fails
Rural economy decline
What is socio economic drought
Agricultural drought less or food shortage, famine and starvation
Humanitarian crisis
Can also be caused by war, poor agricultural practice and population explosion
What happens in a normal , non El Niño year
- trade winds blow over west Pacific Ocean towards Australia and SE Asia
- winds push warm water west, sea levels and temp increase (low pressure)
- Peru experiences high pressure with little rain
What happens in a La Niña year
- extremely strong Trade winds blow west over the pacific towards warm water
- sea level rises 1m in Indonesia
-low pressure develops as warm water heats atmosphere, convectional uplift means heavy rain in Southeast Asia - strong upwelling of cold water in Peru leads to high pressure and extreme drought
What happens in an El Niño year
- trade winds in west pacific weaken and die, reverse direction of flow
- piled up water in west moves east - 30cm rise in sea level in Peru (low pressure and rainfall)
- food chain breaks as eastern pacific warms and currents disrupted - poor fishing conditions
- calm conditions across whole pacific
What is the Sahel region
Vast semi arid region on the southern edge of the Sahara
Stretches across African continent
How many people needed food assistance in the Ethiopian-Eritrean drought 1999-2000
10 million
What socio economic factors exacerbated the 1999 Ethiopian Eritrean drought
- degradation from overgrazing
- deforestation for fuelwood
- high levels of rural poverty
- rain fed agriculture
- population explosion
What physical reasons make Australia drought prone
-low and variable rainfall
- droughts vary in length and size
- close link to El Niño events
- less rainfall each year in the east
- long term climate change
How much of australia’s agricultural output is in the Murray darling basin
50%
Why is Adelaide so vulnerable to drought
Relied on river Murray for 40% drinking water supply
River Murray so overextracted that no water flowed to the mouth
What are the key functions of wetlands
- Temporary water stores which mitigate floods and recharge aquifers
- trap and recycle nutrients and pollutants which maintains water quality
- high biodiversity
What is the impact of drought on wetlands
Limited precipitation leads to deterioration of vegetation, so less interception, infiltration and percolation to groundwater stores
Evaporation increased from lack of protection of surface, transpiration will decrease
How much wetland has been destroyed in Europe and the USA for agriculture
2.5milion km2
What schemes have led to wetland drainage
Jonglei canal project directed white Nile from Sudd swamp to dry South Sudan
How are wetlands being protected now?
1991 Ramsay convention listed 1800 wetlands of national importance to promote conservation
What is a wetland
An area of rash, fen, peak and or water
Area can be natural or artificial, permenant or temporary
Water can be static or flowing, brackish, salty or fresh
How much of earths surface is covered by wetlands
10%
What was the wettest month since records began
Fenruary 2020
What are floods caused by
When discharge is high enough to cause the river channel to overflow and submerge surrounding land
What land is more likely to flood and what type to they experience
Low lying land and small river basins - Both river flooding and groundwater flooding when saturated
Urban areas experience surface water flooding
What is the difference between primary and secondary causes of flooding
Primary - climatological and meteorological
Secondary - more specific factors eg steepness of slopes
Name some primary causes of flooding
- Prolonged heavy rainfall
- seasonal monsoon rainfall
- sinuous jet stream (brings many depressions in one go) eg UK autumn 2015
- snow melt
- glacier melt
- tropical cyclones
Name some secondary causes of flooding
- basins lacking vegetation
- steep slopes
- impermeable rock
- shallow soil depth
- smaller drainage basins experience more rapid drainage
What factors exacerbate flood risk
- farming
- dam building
- urbanisation
- deforestation
How does farming exacerbate flood risk
Compacts soil by ploughing, grazing animals trampling soil, irrigating soil
How does urbanisation exacerbate flood risk
Tarmac, sewers, channel realignment, bridge supports impede channel flow
Why is urbanisation the most significant factor in flood risk
Most cities and towns built on low lying land / flood plains
Combines physical and human factors
How many flood disasters were recorded between 1990 and 2010, what was the main impact?
3000 disasters
200000 deaths
How many people live in flood prone areas
900million
Where do most flood deaths occur
90% deaths in Asia - China, Bangladesh, India, Vietnam
What was the economic damage of flooding to the Uk in December 2015
£1.3Bn
What are annual flood losses worth in Australia
$372million
Name some social impacts of flooding
- death
-disease - property damage
- inspfrastructyre damage
- businesses flooded
- crops fail
Give an example of infrastructure damage from flooding
Cockermouth Cumbrian key bridge connecting the town damaged
Give an example of an impact of businesses flooding
Carlisle mcVities biscuit factory flooded
Temporary loss of 1000+ jobs
What are some positive environmental impacts of flooding
- groundwater recharged
- wetlands filled
- aquatic habitats connectivity increased
- sediment and nutrients redistributed
- breeding triggered
What are negative environmental impacts of flooding
-eutrophication
- pollution from nitrates, chemicals and heavy metals
How does climate change impact the hydrological cycle
Intensification, Acceleration, Enhancement of global hydrological cycle
Differential temperature increases, rainfall pattern changes, alteration to drainage basin cycles
How does climate change impact soil moisture
More linked to precipitation- as precipitation increases then soil moisture increases
How does climate change impact evaporation
Evaporation increasing in Asia and North America
Increased cloud cover could work against this
How does climate change impact the ocean
Where oceans warmer, more evaporation
Limited evidence that more cyclones will appear
How does climate change impact permafrost
Permafrost degradation in northern areas
Releases methane from thaw lakes which accelerates change through a positive feedback loop
How does climate change impact precipitation
Intense rainfall events increased
At the same time - length, frequency and intensity of heatwaves have increased widely, increasing drought
- less precipitation falls as snow, more as rain
How does climate change impact snow
Length of snow cover season decreased
Spring melt occurs earlier- changes river regimes
How does climate change impact surface runoff
Increased hydrological extremes
Both extremes increase runoff rate and reduce infiltration
How does climate change impact glaciers
Glaciers retreating significantly
Dwindling cryosphere water supply
Why is there uncertainty about climate change
- only a partially understood science
- global records incomplete
- tekeconmections make it difficult to distinguish between climate events or ENSO cycles
What is teleconmection
Atmospheric science which refers to climate anomalies being related to each other at large distances
What are emerging patterns of climate extremes?
- more common
- Likely heavier precipitation
- moisture holding capacity of atmosphere increasing
- disaster losses grown more rapidly than precipitation rates or economic growth
What impact will evaporation have on drought
- Increased EVT leads to drought
- droughts becoming more widespread, intense and persistent
- eg in Sahel, southern Europe and south west USA
What factors can affect drought occurrence other than climate change ?
- sea temp changing air circulation and precipitation
- decreasing snow melts and therefore lower soil moisture
- enso impacts
What is water security
The capacity of a population to safeguard sustainable access to adequate quantities of acceptable quality for sustaining livelihoods, human well-being and socio- economic development for ensuring protection against water borne pollution and water related disasters
How does climate change lead to water insecurity
- Loss of stores such as snow, glaciers, aquifers
- increased temp leading to greater EVT - degrades surface water stores and biosphere
- increased intensity and frequency of drought
- more frequent extreme storm events (monsoon, cyclones)
Why could climate change be good for the Sahel
-small increase in precipitation predicted (use in agriculture, industry and domestic )
Why will climate change be bad for Australia
water shortage
Floods and drought
Extinctions
