EQ2-deficits in hydrological system Flashcards
deficit
refers to when input is less than output.
can be caused by natural or human factors
drought
-an extended period a season/years of defiecient rainfall relative to the statistical multiyear average of a region- eg a desert cant be
meteorological drought:
features:
rainfall deficit
-Low precipitation
-High temperatures
-Strong winds
-Increased solar radiation
-Reduced snow cover
meteorological drought:
impacts:
rainfall deficit
-Loss of soil moisture
-Irrigation supply drops
-Reduction in water available for consumption.
hydrological drought:
features:
stream flow deficit
-Reduced infiltration
-Low soil moisture
-Little percolation and groundwater recharge
hydrological drought:
impacts:
Stream flow deficit
-Reduced storage in lakes and reservoirs
-Less water for urban supply
-Poorer water quality
-Threats to wetlands and habitats
agriculture drought:
impacts:
Soil moisture deficit
-Low evapotranspiration
-Reduced biomass
-Fall in groundwater level
agriculture drought:
impacts:
Soil moisture deficit
-Poor yields from rainfed crops
-Failing irrigation systems
-Livestock productivity falls
-Rural industries affected
-Government aid may be required
socio economic drought
features:
food deficit
- loss of natural veg
- increase risk of wild fires
- wind blown soil erosion
- deserfication
agricultural drought
impacts:
food deficit
-Widespread failure of agricultural systems
-Food shortages
-Rural economy collapses
-Rural to urban migration
-International aid required
-Humanitarian crisis
the intertropical convergence zone
(ITCZ)
-band of low pressure around Earth which lies near to the equator
-moves n/s seasonally
- air rises as a result of heat by suns energy, also high evapoartion-causing alternating wet n dry seasons
-the subtropical high pressure zones associated w descending part of convection cell block the high humidity, rain bearing air masses asscoaited w the itcz so pattern is modified.
-EG africa low humdity + if pressure blocks arrival of wet season= drought in sahel
el nino southern oscillation
-change in water body patterns within s hemisphere leading to unusual weather conditions
OR..
-periodic fluctuation in sea surface temp (El Niño) + air pressure of overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean.
-cool water found along peru coast + warm waters found around australia, ENSO causes this to switch (usually occurs every 3-7yrs n last 18months)
-peruvians determine enso occurence based on their anchovy harvest- they prefer cold waters so when it warms the anchovies migrate away
-it can also trigger dry conditions in s+ s e asia, e austarlia + n e brazil
-can weaken annual monsoon in s asia
el nino
la nina vs el nino
-The ENSO pattern in the east-central/tropical Pacific can be in one of three states: El Niño, Neutral, or La Niña
-El Niño =the warm phase 3-7 years (climate change cause more)
-La Niña =the cool phase (droughts)
causes :
drought in brazil
2014-15
normally…
-moist air moves in w direction from s atlantic across amazon basin+ at the andes it turns southwards
in the drought…
-high pressure systems diverted rain bearing winds N away from amazon+prevented them from diverting s from the andes
-heavy rains accured in bolivia, paraguay whilst dry air remained over brazil
impacts:
drought in brazil
2014-15
-water rationing for 4 mill ppl, water supplies cut off for 3 days a week in some towns
-the halting of hep preoduction, which led to power cuts
-the depletion of brazils 17 largest reservoirs to dangerously low levels- some down to 1% capacity
-increase groundwater abstraction, led aquifers to become dangerously low
-reduced crop of arabica coffee beans which pushed up global coffee prices by 50%
climate chnage
drought in california
causes
-annual rain is between 200-500mm-so mainly arid
- la nina droughts
- rainfall shadow from mountains
-
drought in cali
imapcts
-wildfires burned 7 milll acres in 2012
-1 mill ppl lack access to safe water
-reduce soil strength
-high pressure systems
-deplete groundwater supply
-increase in illness
-high demand: grown 37 milliion in 1900-2021: spatial imbalance + agriculture
-colorado river: dams supply 60% of water
- drought happened:2006-2010, 2011-2017, 2020-2022
causes :
drought in sahel
-air pollution made in europe + north america
-lower humidity in africa
-blocking highs + ITCZ
-desertification-land degration + biological productivity
climate change
impacts:
drought in sahel
-6 mill hectares of farmland lost each yr to desertification
-most severe in 2011-12
-rise in annual rain by 16mm by 2080
-temps predicted to rise between 2.5 DC + 4.3 DC by 2080
-sea level rise by 38 cm on atlantic ocean
-crop + livestock die
-unemployement
-soil erosion + less fertile
-vegetation die
human actvity+drought
desertification
-process by which once-productive land gradually changes into a desert-like landscape.
-It usually takes place in semi-arid land on the edges of existing deserts.
-It’s not necessarily irreversible.
-eg sahel
human activity+drought
desertfication in sahel
-CAUSE:water hungry crops like ground nuts were grown + cattle herd sizes ^ as more wells were dug. so grounwater levels fell=drought in 1970s+2005. also drop in rainfall bc of failure of ITCZ
-sistuation made worse by civil wars as Crops, livestock + homes have been deliberately destroyed.
-also pop increase: 3% growth a year
other human causes of drought
- Population growth: rapid pop ^ puts pressure on land to grow more food. Migrants fleeing from one disaster area help to make another.
- Overgrazing: too many goats, sheep + cattle destroy veg cover
- Overcultivation: intense use of marginal land exhausts soil + crops wont grow
- Deforestation: trees r cut down for fuel, fencing + housing. roots no longer bind the soil, + erosion ensues.
- dam developments: colarado dams=mexico drought, and turkey dam
natural causes of destertfication
set in downward spiral by humans
- Changing rainfall patterns w rainfall becoming less reliable, seasonally + annually. occasional drought year sometimes extends to several years.
- vegetation cover becomes stressed + dies, leaving bare soil.
- bare soil is eroded by wind + occasional intense shower.
- When rain does fall, it is often only for short, intense periods. This makes it difficult for the remaining soil to capture + store it.
