EQ2 Flashcards
what are the meteorological causes of drought?
short term precipitation
longer trends
ENSO cycles
what is the UN’s general definition of drought?
an extended period-a season, year, or several years-of deficient rainfall relative to the statistical multi-year average for a region.
what is meteorological drought?
occurs when long term precipitation is much lower than normal. it is region specific since the atmospheric conditions that result in deficiencies of precipitation are highly variable between climate types.
what is agricultural drought?
occurs when there’s insufficient soil moisture to meet the needs of a particular crop at a particular time.
when does agricultural drought usually happen?
after a meteorological drought but before a hydrological drought
what is agricultural drought caused by?
precipitation shortages
differences between actual and potential evapotranspiration
soil water deficits
reduced groundwater and reservoir levels
what is hydrological drought?
occurs when there are deficiencies in surface and subsurface water supplies as measured in rivers, lakes, reservoirs, groundwater etc
what is socio-economic drought?
occurs when water demand for social and economic purposes exceed water availability.
what percent of the world experience some form of drought?
38
what are some examples of places with high drought?
LA, Myanmar, Somalia, Spain, UAE
what are the 3 kinds of atmospheric cell (from equator to pole)
Hadley
ferrel
polar
what is the ITCZ?
belt of low pressure which circles earth generally near the equator, where trade winds of the northern and southern hemispheres come together
what is a trade wind?
a wind blowing steadily towards the equator from the north-east in the northern hemisphere and south-east in the southern hemisphere.
where is the ITCZ in the northern hemisphere summer?
further north
what does the ITCZ cause when it arrives?
wet season
what does the ITCZ cause when it leaves?
dry season
what happens to the Sahel in drought years?
the ITCZ doesn’t move as far north as usual, due to an anticyclone in the north preventing the southwesterly winds from bringing the usual rain.
what happens in the pacific during an el nino year?
warm water moves to west coast of south America.
what happens to Australia during an el nino year?
sinking air causes dry conditions and drought
what happens to the west coast of south America in an el nino year?
warmer waters cause increased rainfall and floods
what happens in the pacific during a la nina year?
v strong trade winds move warm water westwards towards east coast of Australia.
what happens to the east coast of Australia during a la nina year?
increased heat causes air to rise rapidly forming thick clouds, heavy rain, and floods.
what happens to the west coast of south Australia during a la nina year?
there’s a strong swelling of deep cold water. unusually high pressure due to sinking air causes v high dry weather and drought.
what’s causing the aral sea to shrink?
cotton production
what happened to the rivers supplying the aral sea?
were diverted to provide water for cotton farms in Uzbekistan.
how did the shrinkage of the aral sea affect climate?
the aral sea used to keep the climate temperate, now it’s v v hot and dry.
less vegetation-sandstorms, dust storms.
why were jobs lost at the aral sea?
main income used to be fishing.
how did the aral sea shrinking affect public health?
the sand and dust storms blow pesticides from the cotton farms into the city, poisoning people and the environment- TB, stroke, blood pressure. no jobs and hard to get food or water- poverty related illnesses.
what have the Kazakh government done about the aral sea?
built a dam- north aral sea has started to return.
what aquifer did coca cola take and where + when?
Plachimada aquifer in Kerala, 2000
how did coca cola cause water shortages?
dug 6 wells tapping into groundwater in aquifer, by 2004 wells used by villagers had dried up.
what did coca cola do about the water shortages they caused?
drove tankers of fresh water to village.
what are the human causes of drought?
deforestation
overabstraction
overgrazing
overcultivation
what is positive feedback?
a cyclical sequence of events that amplifies or increases change.
what is negative feedback?
a cyclical sequence of events that decreases or neutralises the effect of change on a system.
what is tipping point?
when a system changes from one state to another and is unable to ‘bounce back’.
what is resilience?
the ability of a community to ‘bounce back’ and survive.
what are the physical causes of flooding?
amount+type of rain rock type relief temperature previous weather conditions snowmelt
what is lag time?
difference between peak rainfall and peak discharge.
what factors increase lag time?
permeable rock
flatter ground
afforestation
natural area
what factors decrease lag time?
impermeable rock
steep relief
deforestation
urbanisation
what is surface water flooding?
flooding that occurs when intense rainfall has insufficient time to infiltrate the soil so flows overland.
what is groundwater flooding?
flooding that occurs after the ground has become saturated from prolonged heavy rainfall.
what is flash flooding?
a flood with an exceptionally short lag time.
what is jokulhaup?
a type of glacial outburst flood that occurs when the dam containing a glacial lake fails.
what environments are especially at risk from floods??
low lying parts of flood plains and river estuaries
urbanised areas
small basins
why are river estuaries at risk from floods?
not just prone to river flooding but also groundwater flooding due to ground being saturated.
why are urbanised areas at risk from floods?
more impermeable surfaces-surface water floods+flash floods.
bridges and culverts often reduce river capacity.
why are small basins at risk from floods?
v short lag times.
what are the human causes of floods?
urbanisation
flood plain drainage
deforestation
flood mismanagement
why are flood plains drained?
agriculture
expanding urban areas
how does flood plain drainage increase floods?
reduces natural storage capacity of floodplain, especially where natural wetlands are lost.
land may shrink as it dries, getting glower so more susceptible to flooding.
how might levees increase flood risk?
built to increase channel capacity-may transfer discharge to unprotected areas like choke points downstream.
what were the boscastle floods of 2004 an example of ?
prolonged rainfall floods
what were the physical factors contributing to the boscastle floods?
v small drainage basin (30km2)
ground already saturated
steep relief
at junction of 3 rivers (valency, Jordan, paradise)
what were the human factors exacerbating the boscastle floods?
village car park lies at top: cars were 1st objects to get washed down-caught more material and built up causing huge surges of water when they gave way
how tall was the water surge at boscastle?
10ft
how many people were rescued by helicopters in boscastle?
120
what are the benefits of regular floods in Bangladesh?
replenish groundwater provides nutrient rich sediment aquaculture flushes out pollutants micro-climate control
why is aquaculture important in Bangladesh?
fish export 10% earnings
fish 75% protein
what were the causes of the Bangladesh floods of 2010?
snowmelt from Himalayas monsoon deforestation+conversion of forest hurricanes+cyclones drainage congestion embankments
what was the flood action plan implemented in Bangladesh?
embankments along lengths of major rivers
what were the criticisms of the flood action plan of Bangladesh?
- flooding more sudden and harmful (sudden breaches of water over embankments)
- no research on effect of embankments in nitrogen fixation
- areas of stagnant water created behind embankments
- reduces aquaculture
- displaces people
in 2010 how much of Pakistan was underwater due to flooding?
1/5
what were the physical causes of the Pakistan floods 2010-2011?
global la nina event started around the time of the 2010 monsoon. La Niña warms both water and air masses, increasing the amount of moisture that can be carried in the atmosphere. blocking anticyclone (high pressure) in Russia caused torrential rains in Pakistan as well as unusual Jetstream pattern
what human factors contributed to the Pakistan floods of 2010-2011?
deforestation
illegal logging on steeply sloped areas
Pakistan usually has drought so it has loads of infrastructure built to hold water.
how many people were affected by the Pakistan floods of 2010-2011?
over 20 million
how many people died in the Pakistan floods of 2010-2011?
1600
how many houses were destroyed in the Pakistan floods of 2010-2011?
1.2million
how many schools closed in the Pakistan floods of 2010-2011?
11,000
what were the agricultural sector costs of the Pakistan floods of 2010-2011?
1billion USD
what was a global impact of the Pakistan floods of 2010-2011?
cotton prices rose because the cotton crop failed and Pakistan is the world’s 4th biggest cotton producer
what will climate change do to seasonal snowmelt?
make snowmelt peaks earlier due to the earlier arrival of spring like conditions
what percent of the world’s land mass is now severely affected by drought?
30
