Water EQ2 Flashcards
(41 cards)
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 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
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
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
Name some social impacts of flooding
- death
-disease - property damage
- inspfrastructyre damage
- businesses flooded
- crops fail
What are some positive environmental impacts of flooding
- groundwater recharged
- wetlands filled
- aquatic habitats connectivity increased
- sediment and nutrients redistributed
- breeding triggered
