Water Flashcards
5.2 - Why does it rain?
1) Air rises (containing water vapour)
2) Air cools as it rises
3) Condensation occurs - turns into water droplets
4) If cooling continues it may rain
5.4 - What is meteorological drought?
- a significant deviation from the long term mean precipitation
5.4 - What are the physical causes of drought?
- short term rainfall deficit or by longer term trend-like climate change
- El Nino (short term) - causes drought in Australia
- La Nina - causes drought in South America
5.4 - Describe how the processes of El Nino and La Nina can lead to drought
El Nino
- Trade wind change direction - cold water heads to Australia - high pressure - air descends causing droughts as less rain - warm water heads to south America - low pressure - air rises cools condenses rains - storms
La Nina
- trade winds blow strongly normal direction - excessive low pressure causing storms and floods in Australia - cold water returns to south America - very high pressure - very dry - droughts
5.4 - How do humans cause/contribute to droughts?
- Can’t cause them but can make worse
- Acts as a feedback loop that encourages:
- Population growth
- Overgrazing
- Overcultivation
- Deforestation
5.4 - What is desertification and what is the cycle of desertification?
Desertification - key feature of famine drought
- land degradation in arid and dry sub-humid regions
Cycle
- Natural veg decreases
- Soil left exposed
- sun bakes surface so cracks
- rainwater runs over surface rather than soaking in
- soil can often wash away
- soil degraded losing fertility
- soil worn out - harder to grow crops
5.4 - What are the impacts of drought + judgements on them?
- Famine
- Poverty
- Impact on energy supplies
- Conflict
- Water quality and amount
- Wildfires
J - social impacts often worse in poorer countries, in richer countries more economic
5.4 - case study - The Sahel - how human activity and physcial causes has contributed to drought in the Sahel
The Sahel is a vast semi arid region to the southern edge of the Sahara
Human:
- Over use of aquifers due to increased livestock
- deforestation - wood cut for fuel and building homes - pop growing due to migrants from surrounding civil wars and droughts
- one year out of every 5 brings drought, crop failure and livestock loss to Sudan
Physical
- mean annual rainfall low - nearly all falls in summer
- higher sea surface temp reduces difference in temp between land and sea - weakness monsoon
- El nino triggers dry conditions
5.4 - What is the impact of drought on ecosystem functioning?
Wetlands
- eventual dry out
- soil moisture reduced - soil erosion
- decline in quality of water
- soils oxidise and add carbon to enviro
- loss of species
- increased flooding due to loss of water stores
- extreme dryness = wildfires
5.4 - What does Ramsar do to protect wetlands?
Half of the worlds wetlands have already been destroyed
Ramsar:
- The Ramsar Convention on wetlands was set up in 1991 and protects 1800 wetland areas around the world
- Brings people together to manage wetlands and protect them
- Workers focus on wiser use of water
- Net worker of international cooperation
5.5 - What are the 4 meteorological causes of flooding
1) Intense storms
2) Heavy or prolonged rainfall
3) Extreme monsoon
4) Snowmelt
5.5 - Example of a place that is highly at risk of flooding
Bangladesh - can experience all 4 meteorological causes of flooding
- But also has lots of secondary factors - Lots of large rivers - Meghna, Ganges and Padma - Flat land - 50% is 12.5m or below above sea level - Highly populated - 80% of population vulnerable to flooding
5.5 - Explain the meteorological reasons for flooding on a global scale
4 causes of flooding, storms, prolonged rainfall, monsoons and snowmelt
- storms - particularly tropical ones - 5-30degrees north and south of equator - cause flooding due to heavy rainfall or storm surges
- prolonged rainfall - low pressure systems - common in UK - ground saturated - surface run off quicker large amounts of water in rivers
- monsoons - common in asia - large amount of rainfall in short amount of time
- snowmelt - rapid snow melt frozen ground no infiltration - all goes to river
5.5 - What are the two main causes of flooding by humans?
Urbanisation
Deforestation
Hard engineering mismanagement of rivers
5.5 - What are the socio-economic and environmental impacts of flooding?
Envrio:
- Destruction of aquatic plants and introduction of pollution from nitrates
- Recharge groundwater - Especially good for countries that rely on groundwater supplies
- Soil replenishment
- Wildlife can be poisoned by polluted waters eg hedgehogs and moles
Socio-eco:
- Post - flood morbidity worse in LIC’s - water borne diseases
- Direct structural damage to property - hits all stage of development counties
- 90% of all flood deaths occur in Asia
- Crops, livestock and agricultural infrastructure suffer major damage - rural regions hit worse - Subsistence farming - direct loss of food
- worse if water polluted
- Ec impacts worse if no insurance
- Worse in cities - more infrastructure damaged
- Deaths higher in poorer regions
