Water Cycle Flashcards
What are the human causes of drought?
DEBBIE DOCTOR IS PRETTY HOT
- Deforestation
- Dam construction
- Irrigation
- Population growth & over extraction
- Human induced climate change
Why does Australia suffer from drought?
- Anthropogenic factors: climate change and deforestation
2. Physical factors: El Nino
Australia CO2 per capita in 2013?
25 metric tonnes of CO2 per capita in 2013!
Australian deforestation?
5000 sqkm of bushland cleared annaully
Has lost 25% of rainforest and 45% of open forest in last 250 years!
Major last ENSO event?
2014-16
What is a wetland?
An area of marsh, fen, peatland or water
Whether natural or artificial
Permanent or temporary
With water that is static/flowing/ fresh/ brackish/ salty
How much do wetlands cover?
Wetlands cover 10% of the Earth’s surface
What are the functions of wetlands?
TGHP (Thank God He Phit)
- Act as temporary water stores (mitigate, protect)
- mitigates river floods downstream
- protect land from destructive erosion - Giant water filters (traprec and maintain)
- trapping and recycling nutrients
- maintaining water quality - High biological productivity
- support diverse food web - Providers
- resources e.g. fish
- services e.g. hydrology
What is the impact of drought on wetlands?
- Less precip = less interception of veg = decline
2. Less infil & percolation = water table levels fall (water for wetland = groundwater = cannot be replenished :(
Resilience of wetlands?
During Saddam Hussein’s dictatorship, the marshlands in Southern Iraq turned to deserts
BUT after his overthrow in 2003 - marshes restored to being super healthy! :) SUPER RESILIENT
When does flooding occur?
If the discharge is of sufficient quantity to cause a body of water to overflow its channel and submerge the surrounding land
Where are the areas most at risk from flooding?
- Low lying parts of flood plains
- Low lying areas partially urbanised with impermeable surfaces
- Small basins - flash flooding
Types of flooding?
- Groundwater flooding
- due to saturation from prolonged heavy rainfall - Surface water flooding
- insufficient time to infiltrate soil, so flows on surface - Flash flooding
- short lag times
- v. intense convectional storms
What is the recurrence interval?
The estimate of the likelihood of an event
Physical causes of flooding?
- Intense storms over a short period of time
- flash flooding
- usually ground is baked with no prior rainfall
- cannot infilitrate
- surface run off - Unusually excessive precipitation over a long period of time
- causes saturation of the soil
- increased overland run off
- usually associated with low pressure systems e.g. UK
- UK = usually autumn - early winter
- areas of flood risk in UK = Cardiff & London - Extreme monsoonal rainfall
- e.g. Asia = Bangladesh, India
- ITCZ = June - August
- Around 70% of annual rainfall in 100 days!
- Half of the country is less than 12.5 metres above sea level! - Snowmelt
- most common flooding is when subsoil is still frozen, cannot infiltrate, surface run offffff
- late spring, early summer
- Ob and Yenisei = annual flooding in Siberia
- glacial outburst floods/jokulhlaups too!
ITCZ movement?
December-January: NORTH
June - August: SOUTH
ITCZ movement?
December-January: NORTH
June - August: SOUTH
Why do floods frequently flood esturine areas?
High river flows interact with high tidal conditions @ coast
What are the physical factors affecting flood levels?
- Slope
- steeper gradient = more run off = more flood risk - Vegetation
- more veg = higher interception = more infilitration etc = reduces lag time = less flood risk - Soil type
- permeable soils e.g. Sandy (3-12mm/hr) = greater infilitration = less surface run off = less flood risk (but Clay = 0.4mm/hr = flood!)
Human causes of flooding?
DUC
don’t u cock
- deforestation
- urbanisation
- anthropogenic climate change (melting glaciers & snowmelt & more intense weather events)
Human factors on DB?
Don’t u dare fuck off DUD
- dam construction
- urbanisation
- deforestation
- farmland and irrigation
- overextraction
When was Cape Town Water Crisis?
2017-18
Physical factors on DB?
Catherine steals girlfriend really vigourously
- climate
- soils
- geology
- relief
- vegetation
Urbanisation of UK?
82% of pop live in towns and cities