EQ2 Flashcards
define drought
a ‘shortfall’ or deficiency of water over an extended period, usually at least a season
define meterological drought
shortfalls in PPT as a result of short term variability within the longer-term average overall
define agricultural drought
the rainfall deficiency from meteorological drought leads to deficiency of soil moisture and soil water availability, which has knock on effect on plant growth and reduces biomass
define hydrological drought
associated with reduced stream flow and groundwater levels, which decreases because of reduced inputs of PPT and continued high rates of EVP, it results in reduced storage in lakes and reservoirs, often marked with salination and poorer water quality
what does PPT stand for (important)
PRECIPITATION
what does EVP stand for (important)
EVAPOURATION
what are the major features of meteorological drought
Rainfall deficit
-low precipitation
-high temperatures
-strong winds
-increased solar radiation
-reduced snow cover (rivers will not get snowmelt input – rivers drop)
what are the major features of hydrological drought
Stream flow deficit
-reduced infiltration (ground is so hard water can’t infiltrate)
-low soil moisture
-little percolation and groundwater recharge decreases
what are the major features of agricultural drought
Soil moisture deficit
-low evapotranspiration
-plant water stress
-reduced biomass
-fall in groundwater levels
what are the major features of famine drought
Food deficit
-loss of natural vegetation
-increased risk of wildfires
-wind-blown soil erosion
-desertification
what are the major impacts of meteorological drought
-loss of soil moisture
-supply of irrigation water declines
what are the major impacts of hydrological drought
-reduced storage in lakes and reservoirs
-less water for urban supply and power generation - restrictions
-poorer water quality
-threats to wetlands and wildlife habitats
what are the major impacts of agricultural drought
-poor yields from rain-fed crops
-irrigation systems start to fail
-pasture and livestock productivity declines
-rural industries affected
-some government aid required
what are the major impacts of famine drought
-widespread failure of agricultural systems
-food shortages on seasonal scale
-rural economy collapses
-rural-urban migration
-increased malnutrition and related morality
-humanitarian crisis
-international aid required
what are the physical causes of meteorological drought
-Natural variations in atmospheric condition
-El nino
what are the physical causes of agricultural drought
-reduction ppt and increased evaporation
what are the physical causes of hydrological drought
-reduction in ppt and increased evaporation
what are the human causes of meteorological drought
-deforestation
-global warming
what are the human causes of agricultural drought
-overgrazing
what are the human causes of hydrological drought
-diversion of water for irrigation or dams
-over abstraction of rivers, lakes and aquifers
what are el nino and la nina
El Niño and La Niña are changes in this circulation, linked with changes in atmospheric processes
what does a normal year look like compared to an el nino year
Strong trade winds
Pushes water to australia (warm)
Upwelling of cold water towards south america
Upwelling is important for fish stocks in Peru
what does an el nino year look like
Weak trade winds
It goes the other way pushing warm water to south america
Warm water over whole pacific ocean
The normal east to west trade winds over pacific are disrupted and warm water goes eastwards
No upwelling on South American coast (affects fishing industry)
Air pressure over West coast of S. America becomes low and air over west Australia high pressure
what does an la nina year look like
Exaggerated normal
Very strong trade winds
Pushes large amounts of warm water to Australia (west)
As warm water is pushed westwards sea levels rise by up to 1m around Indonesia and Philippines. Strong uplift of air leads to heavy rain!
Air pressure is unusually high over the west coast of S.America and low over eastern Australia
A La Niña episode may, but does not always, follow an El Niño event
define positive feedback
a cyclical sequence of events that amplifies or increases changes
define negative feedback
a cyclical sequence of events that damps down or neutralises the effect of a system
define tipping point
when a system changes from one state to another
define resilience in terms of systems
the ability of a system to ‘bounce back’
how does drought affect rainforests
hint: use words like pos feedback, resilient etc
Rainforests recycle half of their rainfall, but the positive feedback loop of deforestation + less rainfall is reducing the ability of the rainforests to regenerate → making the rainforest ecosystem less resilient
what is the affect of thinning forests
Reduced soil water storage
Reduced evapotranspiration
Changing weather patterns
Lower precipitation
what does the combined risk of climate change, el nino and deforestation leads to?
drought occurring more frequently
what does drought occuring more frequently lead to?
The amazon rainforests capacity to absorb carbon will decline
Regional water cycles will change and soil temperatures will increase
The amazon rainforest will be replaced with savannah-like grasslands
More wildfires will increase the level of carbon in the atmosphere
Reduced rainfall will threaten dependency on HEP (which generates 70% of its electricity)
The world will lose a major carbon sink and source of moisture
what are the impacts of drought on wetland areas
vegetation will deteriorate due to decreased interception
less infiltration and percolation to the ground water stores, causing the water table to fall
Evapouration will continue and may increase due to less vegetation cover while transpiration rates will decrease, making wetlands less functional
Dedication (the process of extreme drying) can also lead to wildfires
define groundwater flooding
flooding that occurs after the ground has become saturated from prolonged heavy rainfall
define surface water flooding
flooding that occurs when intense rainfall has insufficient time to infiltrate the soil, so flows overland
define flash flood
a flood with an exceptionally short lag time - often minutes or hours
what environments are more susceptible to flooding
Especially in urban areas where ground is impermeable
Small basins , especially in semi-arid/arid areas. Associated with very intense convectional storms Infiltration is limited with steep unvegetated slopes allowing overland flow to develop very quickly
what are the meteorological causes of flooding
Unusually heavy or prolonged rainfall
Intense storms leading to flash flooding
Extreme monsoonal rainfall
Snow melt
what is the meteorological causes of unusually heavy or prolonged rainfall
The position of the jet stream causes flooding. Jet streams are the driving force which determine the direction of depressions and their high speeds.
what is the meteorological causes of intense storms leading to flash flooding
Occasionally, dramatic floods occur following intense torrential storms. The intensity of the rainfall exceeds the capacity of the river to cope with amount of water → flooding occurs
what is extreme monsoonal rainfall
Monsoon rains are often heavy, but in this case are larger low pressure systems brought heavier rain than usual.
Occurs across south and southeast asia between May - Sept.
how does snowmelt lead to
Flooding can occur when snow melts and the resulting water cannot infiltrate into the soil or ground surface.
how does human exacerbate (make things worse) flood risk
A combination of economic growth and population movements have caused many floodplains to be built on and many natural landscapes to be modified for agricultural, industrial and urban purposes
examples of human causes that increase flood risk
Creation of impermeable surfaces – roofs, pavements, roads and car parking space. It has been estimated that in London, the land taken up by car parks is around 25 km^2 as around 60% of residents have paved over their front gardens for parking.
Speeding up the drainage of water in built up areas via artificial conduits e.g drains and sewers
Impeding channel flow by building alongside the river e.g building bridge supports and carrying out structural engineering by building levees
Straightening channels (realignment) to increase the flow, which results in flooding downstream – this could be regarded as mismanagement in some ways. Resectioning by dredging involves widening and deepening the channel to increase efficiency by increasing capacity and moving water away at a faster rate – but at considerable environmental cost
Changing land associated with agricultural development.
Deforestation, overgrazing, ploughing or drowning wetlands usually occurs upstream from urbanised flood plains, which has a knock on effect downstream with increased run-off and increased levels of sediment (which are washed into rivers and block river channels)
what are the socioeconomic impacts of flooding
Socioeconomic impacts:
Floods cause death due to drowning or in certain countries poisonous snakes
Water borne diseases, psychological stress can lead to post flood morbidity
Direct structural damage to property in countries of all levels of development
Post flood concerns over reduced property value when flood prone properties are resold
Crops, livestock and agricultural infrastructure suffer major damage in rural areas
Direct loss of food supplies = potential famine and also lead to rising food prices due to scarcity as crop shortages occur
Loss of livelihoods as businesses due to flooding
Areas reliant on tourism will suffer as people cancel holidays
what are environmental impacts of flooding
Intense flooding caused by excessive overland flow can oversupply sediment and nutrients with possible eutrophication and the destruction of aquatic plants as wella s introducing pollution degrading aquatic habitats as wildlife is poisoned
Environmental impacts
There are some positives as natural ecosystems flood play an important role in maintaining biodiversity within ecosystems.
Floods recharge groundwater systems, fill wetlands, increase connectivity between aquatic habitats, move sediment and nutrients
→ for some species floods trigger breeding, migration and dispersal
what evidence is there that climate change causes flooding
A consistent result across climate model projections is high precipitation extremes in warmer climates
As temperatures rise so does the likelihood of precipitation falling as rain rather than snow increases
A 4 inch sea level rise could double flooding frequency in many parts of globe
- Catastrophic for communities and ecosystems
- Eroding coastline worsens impacts
E.g Hampshire village of Hambledon, underwater 6 weeks insurers estimated costs at £1bn
Researchers found that the emissions increase odds of floods occurring
future impacts of flooding
As precipitation intensity increases almost everywhere, especially mid to high latitudes, increases risk of flash and urban flooding → adapt storm drainage systems to accommodate inc rain intensity due to climate change
Rapid melting of glaciers can lead to flooding of rivers + formation of glacial melt water lakes creating outburst flood
The regions most at risk to increased flooding frequency is northern Europe
evidence of climate change causing drought
Climate change is likely to influence precipitation, temperature and potential evapotranspiration and through their combined effect, the occurrence and severity of drought
In the past 30 years droughts have become more widespread, more intense and persistent – could it be due to human factors
Research studies have proved inconclusive globally but southern Europe, south western America and the Sahel seem to have higher incidence and intensity of drought
The occurrence of droughts seems to be determined largely by changes in sea surface temperatures, especially the tropics through changes in atmospheric circulation and precipitation amount
Droughts can persist through a positive feedback where very dry soils and diminished plant cover can further suppress rainfall in an already dry area
future impacts of climate change effects on drought
Future Impacts:
Rise in overseas risks for the UK as there’s a rising need for military intervention → climate related migration and potential violent inter-state conflict over scarce resources
Increased temperatures can amplify the impacts of drought, increased evaporation from soil → makes periodic droughts worse than what it would be under cooler conditions
Early snow melt due to increased temperature can lead to water supply being increasingly out of phase with water demand
Southwest america is considered one of the most sensitive regions in the world for increased risk of drought caused by climate change
