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
5.4 - What is a hydrological drought?
major deficit in supply and availability of surface water
5.4 - What is an agricultural drought?
major deficit in soil moisture as a result of climate change and hydrological deficits
5.4 - What is a famine drought? Also called a socioeconomic drought
During a meteorological drought using groundwater is an adaptive approach but can lead to aquifer depletion during extended droughts
5.4 - What is a famine drought? Also called a socioeconomic drought
During a meteorological drought using groundwater is an adaptive approach but can lead to aquifer depletion during extended droughts
5.4 - What are wetlands and some examples of wetlands?
Areas where water covers the soil for all or most of the year
Examples
- Inland - lakes, rivers
- Coastal - mangroves, coral reefs
- Human made - ricer paddy, fish pond
5.4 What are the functions of wetlands/why are the important?
- purify water + improve water quality
- flood water storage - acts like a sponge
- coastal buffer - prevents erosion
- carbon store
- agriculture relies on it on irrigation
5.4 - How does drought cause forest stress?
- less water intake - due to less water
- less carbon intake due to less photosynthesis cause of less water
- increased susceptibly of tress (pine) to fungal diseases
- increase drought = little time to recover = tree die-back
5.4 - What is resilience in species like?
- varies depending on range of tolerance of species
- many can quickly recover from seasonal drought
- however long term = permanent loss of some wetlands
5.5 - What is heavy or prolonged rainfall caused by?
- low pressure systems moving across a country
- depressions in UK - autumn early winter
- unusual position of jet stream - high pressure systems blocked so low pressure ones stay in one place
5.5. - What are intense storms caused by?
- caused by low pressure
- often but not always convectional rainfall
- common in mountain areas and semi arid areas
- can lead to flash flooding - short lag time (mins/hours)
- Boscastle UK Aug 2004
5.5 - What causes extreme monsoons?
- causes flooding
- usually brings 70% of country’s rainfall in 100 days July-sept
- India received 10% more rain than usual in Sept 2019
5.5 - What are the causes of snowmelt?
- caused by increase in temp - melts snow - adds to river as ground often still frozen - so limited infiltration
- spring - Siberia - Himalayan region
5.5 - What are secondary physcial factors of flooding?
DO NOT CAUSE FLOODING BUT CAN MAKE IT WORSE
- River basin characteristics
- Geology
- Soil
- Vegetation
- Topography
5.5 - How does Urbanisation and deforestation cause flooding?
- impermeable surfaces - less water infiltrates - surface run off quicker
- Drains and sewage system speed up the movement of water to rivers
- Bridges - some designs cause obstacles for flood flow by reducing the cross-sectional area of the river and can be obstructions to debris that then create a barrier so water builds up and overflows
- Deforestation - when cities are built - trees are often cut down so more water gets to the river as less is intercepted by trees and it reaches the river more quickly
5.5 - How does Urbanisation and deforestation cause flooding?
- impermeable surfaces - less water infiltrates - surface run off quicker
- Drains and sewage system speed up the movement of water to rivers
- Bridges - some designs cause obstacles for flood flow by reducing the cross-sectional area of the river and can be obstructions to debris that then create a barrier so water builds up and overflows
- Deforestation - when cities are built - trees are often cut down so more water gets to the river as less is intercepted by trees and it reaches the river more quickly
5.5 - How does hard engineering mismanagement of rivers cause flooding?
Hard engineering mismanagement
- Dams - sediment is trapped behind in reservoir - means less water can be stored in reservoir - can lead to flooding if not regularly removed
- River embankments or Levees - make the river capacity bigger so flooding is less likely but if they fail then the flooding will be even worse - Hurricane Katrina
- Channelisation - straightening the channel means water moves quickly so less likely to flood but can cause flooding further downstream. Concreating the sides of a river will speed up the flow but again can cause problems further downstream - York 2019
5.6a+b - What are the possible changes to global hydrological cycles?
- increasing anthropogenic (human) greenhouse gas emissions
- increasing heat trapped in atmosphere
- increasing avergae air and sea surface temp
Increase - evaporation - condensation + cloud cover - precipitation in low pressure regions (tropics) - flood risk there too - intense high pressure systems - incidence and severity of drought Decrease - snow and permafrost, ice cover - humidity and precipitation in subtropics/high pressure regions
5.61+b - What are some key findings relative to trends in water cycle componenets?
precipitation input - increase in tropics and higher latitudes - decrease 10-30 degrees north and south of equator - more fall as rain not snow in northern regions
Evapo/transpiration - actual increase in large areas of Asia + North America
Soil moisture - ambiguous
Runoff and stream flow - evidence suggest increase in hydrologic events - more intense rainfall = increase of both
Groundwater - evidence limited
Wetland storage - changes occurring but cannot be conclusively linked to climate change - regional variations have been linked to regional changes in climate eg Lake Chad
Snow - length of snow cover decreasing - last 50-100yrs spring melt occurred earlier
ice - strong evidence glaciers have retreated globally since end of Little Ice Age
5.6a+b - What are some key findings relative to trends in water cycle components?
precipitation input - increase in tropics and higher latitudes - decrease 10-30 degrees north and south of equator - more fall as rain not snow in northern regions
Evapo/transpiration - actual increase in large areas of Asia + North America
Soil moisture - ambiguous
Runoff and stream flow - evidence suggest increase in hydrologic events - more intense rainfall = increase of both
Groundwater - evidence limited
Wetland storage - changes occurring but cannot be conclusively linked to climate change - regional variations have been linked to regional changes in climate eg Lake Chad
Snow - length of snow cover decreasing - last 50-100yrs spring melt occurred earlier
ice - strong evidence glaciers have retreated globally since end of Little Ice Age
5.6a+b - What might happen in the UK due to climate change?
- temps will increase especially in summer
- more intense rainfall - increase surface run off - more flash floods in urban
- sea levels rise - increase of coastal flooding
- Decrease in infilitration 0 increase flooding and high flows
- decrease in groundwater - water scarcity may increase
- fewer days of snow and lying snow - impact on skiing industry
5.6a+b - What might happen in the UK due to climate change?
- temps will increase especially in summer
- more intense rainfall - increase surface run off - more flash floods in urban
- sea levels rise - increase of coastal flooding
- Decrease in infilitration 0 increase flooding and high flows
- decrease in groundwater - water scarcity may increase
- fewer days of snow and lying snow - impact on skiing industry
5.6a+b - what are the impacts of climate change on the Ganges river (India)?
Impact on hydrological cycle - worse tropical storms = increase precipitation
- less snowfall + more melt - short term higher river flow - long term no ice stores
- increased winter droughts
Social - 70% of rural pop relies on Ganges for irrigation = reduction in food supply - reduction in water security - water pollution - 400mil depend on water
Econ- fall in GDP as trade in crops declines - water needed for industry, coca cola may leave = lower FDI - opportunity cost of investment in flood management
enviro - more landslides, polluted ecosystems due to metals in floods - recharge groundwater stores + enrich soil with nutrients if not polluted
5.6a+b - what are the impacts of climate change on the Colorado river (USA)?
Impact on hydro cycle - precipitation levels will decrease - 37 degrees north of equator - transpiration decrease less veg - wetlands (lake storage) decrease so will river flow - decreased by 20% compared to last century
Social - high unemployment in agric sector - rising inequalities - over 4mil people rely on river for water
Econ - food prices will rise, personal wealth decrease + job losses in agri sector - may reduce GDP of certain states - around 1tril of econ activity each yr comes from rivers
Enviro - increase use of groundwater = depletion - droughts cause PH of soil turn more acidic - wetlands dry up - veg may die out therefore decrease in biodiversity
5.6a+b - what are the impacts of climate change on the Amazon?
Impact on hydro cycle - increase precipitation in wet season = increased river flow - drought more of a problem major ones in 2005/10/15 - deforestation high 1/5 of amazon rainforest cur down since 1950 - lack of trees = less evapotransp - less precipitation - exposed soil = fast erosion
Social - indigenous people inhabiting may leave as food security and water security decreases - loss of homes and culture - loss of land to farm
Econ - increase risk of fires - reduce tourism + damaging crops + infrastructure - increase soil may lead to lower crop yield so reduced GDP
Enviro - increased droughts = forest dieback - 200 bil tons of carbon stored - would cause feedback loop of increase temps further leading to a loss of trees that store carbon - loss of biodiversity - 30 mil species - many endemic species
