Water Cycle eq2 Flashcards
define drought
extended period of deficient rainfall relative to the statistical average for a region measured iver a very long period of time
What are the causes of drought?
- dams
- deforestation
- ENSO cycles
- changes in precipitation patterns
- irrigation (65%)
4 types of drought
- agricultural drought
- socioeconomic drought
- hydrological drought
- meteorlogical drought
what makes an area more vulnerable?
- if they are directly dependant on the land
- poverty
- lack of preparedness
What are the economic impacts of drought?
- reduced water levles
- decreased agricultural productivity
What are the environmental impacts of drought?
- fire hazard
- soil erosion
What are the social impacts of drought?
food shortages
4 key causes of meterorlogical drought
- natural variations in the atmosphere
- El Nino events
- Changing land use
- Climate change creating regional and local effects
3 atmospheric circulation cells
- polar
- ferrel
- hadley
intertropical covergence zone
Sometimes the subtropical high pressure zones, associated with the descending parts of the convection cell (Hadley cell) block the high humidity, rain bearing air masses associated with the ITC2, so that the pattern is modified
mid-latitudes blocking anticyclones
meterological drought
- low air pressure affected by jett streams
- high pressure areas from tropics move northwards
- stable weather conditions with little precipitation
- block weather systems for up to 2 weeks
- normal precipitation greatly reduced
normal conditions in the pacific
- warm water
- Australia
- low pressure
- risk of flooding
- cold water
- south america
- high pressure
- risk of drought
El Nino conditions in the pacific
- warm water
- south america
- low pressure
- risk of flooding
- cold water
- australia
- high pressure
- risk of drought
El Nina conditions in the pacific
- warm water
- Australia
- low pressure
- risk of flooding
- cold water
- south america
- high pressure
- risk of drought
(enhanced normal conditions)
direct human causes of drought
taking water direclt from a store (abstractation)
indirect human causes of drought
altering hydrological processes (deforestation)
Brazil
- over abstractation of surface-water resources and groundwater aquifers
- drought particularly affected Sao Paulo as groundwater ran low
- people began to drill illegal wels due to high fees
- drought caused stress to amazon
The Sahel, Africa
- droughts of the 20th century were cased by air pollution which caused atmospheric cooling
- could have been casued by higher sea level by anthropogenic climate change
- dry areas being converted into farmland to feed high population
what are wetlands?
areas of land which is saturated with water either permenantly or seasonallt eg swamps, bogs and fens
what are forests?
dense community of trees, highly valuable for goods and services eg carbon sequestation and food
droughts impact on wetlands
water supply reduces, leads to habitiat loss
Soil moisture reduced, leads to soil erosion and reduced ability to store water
droughts impact on forests
die back of species, regulation of climate change due to carbon sequestation, pine bark beetles attack trees
droughts impact on animals in wetlands
birds and bugs show varying responses, can eliminate species, disrupt food webs
droughts impact on forest animals
forest fires can lead to death of species eg nearly 3 billion animals habve dies or been dispalced
4 types of flooding
- monsoons
- prolonged rainfall
- flash flooding
- snowmelt
monsoons
Occurs across Southeast Asia between May and September. Larger than normal low-pressure systems.
The monsoon climate results in high annual rainfall totals exceeding 1.5 m (5 ft) in many places
prolonged rainfall
- ground has become saturated from prolonged heavy rainfall
- leads to more water entering the river channel, increasing the likelihood of flooding.
- Days of intense and prolonged rainfall are likely to increase with global warming.
- The 2014 Somerset floods resulted from 350mm of rainfall in one month.
flash flooding
- A flood with an exceptionally short lag time - often minutes or hours
- Flash floods can carry large debris such as boulders. This combination can cause heavy structural damage to homes making them uninhabitable and can carry away large pieces of property such as vehicles.
- Boscastle floods in 2004 - The village of Boscastle in Cornwall experienced flash flooding on 16 August 2004 when an exceptional amount of rain fell over eight hours.
snowmelt
- A type of glacial outburst flood that occurs when the dam containing a glacial lake fails.
- Rapid snowmelt can trigger landslides and debris flows.
- Increased water runoff due to snowmelt was a cause of many famous floods. One well-known example is the Red River Flood of 1997, when the Red River of the North in the Red River Valley of the United States and Canada flooded.
urbanisation
anthropogenic causes of flooding
- impermeable surfacees decrease infiltration rates
- increase surface runoff into rivers
- shortens lag time as water is directed at river
- eg by bridges
deforestation
anthropogenic causes of flooding
- reduces interception and evapotranspiration
- increases surface runoff
- exposes soil to erosion
- increases river sediment load and deposition
- reduces rivers capacity to hold water
- eg Tibet deforestation caused flooding in Bangladesh
floodplain drainage
anthropogenic causes of flooding
- provides agricultural areas in developed countries
- reduces natural capacity of floodplain
- land shrinks as it dries out
- more susceptible to flooding
flooding mis-management
anthropogenic causes of flooding
- alterations at one point of a drainage basin can cause consequences downstream
- hard engineering designed to reduce frequency of floods eg channel straightening and embacnkments
India
- seasonal monsoons are vital for half the populatio who work in agriculture
- major 2017 flood event caused 1200 deaths
- long term vulnerability increasedd
japan
- 5m deep floods in area already recovering from earthquake
- 225 deaths from landslides
- trains cancelled left people stranded
general impacts of flooding
- lack of productivity
- displacemement of people
- loss of life
- spread of waterborn diseases
- strain on emergency servicfes
- homelessness
- transportation cancelled
- damaged infrastructure
UKs climate change by 2050
- wetter winters due to low pressure
- dryer summers
- high water levels due to thermal expansion and melting glaciets
snow
UKs climate change by 2050
reduce
river flow
UKs climate change by 2050
high and flooding
climate models predict tht climate change could cause
- precipitation to become more variable
- increased risks of droughts and floods
- create uncertain water supply
