me water cycle

• types of drought -

  • meteorological - degree of dryness compared to what is considered to be normal precipitation levels for that area, climate and season
  • agricultural - insufficient water for crops, leading to wilting or loss of crops without irrigation
  • hydrological - when drainage basin suffers shortfalls such as reduced streamflow or an increase of river flow into the reservoirs
  • socio-economic - when there's demand for water to be used for social and economic purposes such as crop irrigation or when HEP exceeds water availability
• physical causes of drought: ENSO: el nino -

  • events happen every 3-5 years where winds weaken across the South Pacific Ocean and reverse direction
  • warm water moves to the South American coastline where lower air pressure causes large increases in rainfall, promoting the potential for flooding
  • australasia has cooler than normal ocean temperatures and is subject to high air pressure - results in little rainfall and an increased risk of drought
• physical causes of drought: ENSO: la nina -

  • low air pressure descends on Southeast Asia and Australia leading to increased rainfall and risk of flooding
  • South America receives high air pressure which leads to reduced rainfall and increased likelihood of drought
• physical causes of drought: short term precipitation deficit -

  • can be short-term precipitation deficit in places when the cycle that creates clouds is interupted
  • water deficit may be experienced in areas that are used to low air pressure systems and have a change of weather front to experience a high air pressure system
  • cool sinking air in high air pressure systems does not have the ability to form clouds and produce precipitation
• human causes of drought: Brazil -

  • 2014-2015 - industries, farmers and domestic users in Brazil increasingly used groundwater - until rivers began to run low
  • poor and rural communities suffered because they only had access to groundwater because of rivers running low
• human causes of drought: Brazil causes of over-abstraction -

  • brazils government introduced a charge for drilling wells of around US$35,000 - US$100,000
  • residents drilled illegally because they couldn't afford the charge - meaning water abstracted was not monitored
  • hydrologists believe the governments official records of wells drilled in 2014 only represent a 1/3 of the total - 70% of wells were illegal
• human causes of drought: Brazil problems with over-abstraction -

  • illegal wells are shallower and so haven't percolated deep into the bedrock
  • water from illegal wells is less filtered by bedrock and may contain industrial and agricultural pollutants with higher levels of bacteria
  • increase in poor sanitation and water-borne diseases happens if the water is not filtered further
• drought = happens when an area suffers from a water deficit - if rainfall falls well below average for a specific place than a deficit can happen
• impacts of drought on ecosystems -

  • ecosystem functioning = the biological, chemical and physical processes that take place in an ecosystem
  • ecosystem resilience - how capable the ecosystem is of surviving changing water levels
  • deserts and semi-arid areas are the most resilient to drought
• impacts of drought: rainforests -

  • prolonged periods of drought lead to forest stress
  • younger trees die as a result of drought - reduces canopy cover
  • reduction of canopy cover leads to less interception + infiltration + decreases evapotranspiration - means less water vapour and rainfall reduces
• impacts of drought: forests -

  • forests exposed to tropical sunlight with dead vegetation and a mass of dry organic material can easily set alight
  • lightning storms and high winds can then turn a small fire into a wildfire
  • Croatia summer 2017 - suffered from 2.5 months of no rainfall - led to widespread drought and wildfires that were hard to manage - water bombing planes were donating from nearby countries to control the flames
• impact of droughts: wetlands -

  • drought increases the likelihood of tree mortality
  • decrease in vegetation reduces the habitat for wild and farm animals
  • birds and wetland vegetation respond to drought differently
  • can change communities by eliminating species and having knock-on impacts on the rest of the food chain
  • likelihood of wildfire increases
• impacts of drought: Suffolk wetlands -

  • species such as snipe and thrush are impacted by the dry soil surface which is present during a drought
  • snipe and thrush are less able to penetrate the dry soil to reach the invertebrates they feed off
• human causes of flooding: removal of vegetation -

  • ground cover decreases, meaning that interception from the plants and their leaves is reduced - water will now just reach the ground
  • removal of plants reduces infiltration - with less infiltration and interception there is an increase in surface runoff
• human causes of flooding: agriculture -

  • as demand for food increases so does demand for agricultural land
  • increasingly farms are made on deforestation sites - eg the amazon
  • agricultural practices increase surface runoff and the amount of soil exposed - leading to soil erosion - sediment from the erosion is transported to the river
  • rivers water capacity is reduced by the sediment, increasing the likelihood that the river will burst its banks
• human causes of flooding: urbanisation -

  • leads to the removal of vegetation resulting in an increase in surface runoff
  • increase in impermeable man-made surfaces (eg concrete, tarmac and tiles) - lead to no infiltration and so all rainfall experiences runoff
  • runoff enters the drainage system which quickly takes the water to rivers and waterways - significantly reduces the lag time and promotes reaching a high peak discharge
• human causes of flooding: floodplain drainage -

  • floodplain land is flat and fertile making it desirable agricultural land - but a target for floods
  • in many countries this land is drained to provide this - but the process of drying out the wetlands destroys habitats
  • drying out process leads to the area shrinking and lowering - can actually increase the likelihood of the areas being subject to floods
• human causes of flooding: river management -

  • river management (especially hard engineering systems) is meant to provide protection from flooding - poor management can have the opposite effect
  • channelisation (when river is widened or deepened) and straightening the river (by cutting off meanders) has actually increased flood risk on the river Mississippi - levees and man-made channels restrict the river, making it more likely to burst its banks
• meterological causes of flooding -

  natural flooding is caused when a rivers discharge increases until the river bursts its banks

  flooding can be caused by an increase in rainfall or an increase in surface runoff water
• meteorological causes of flooding: flash flooding -

  • happen quickly and frequently without warning
  • low air pressure systems can create intense tropical storms and thunderstorms that produce heavy rainfall
• meteorological causes of flooding: prolonged and heavy rainfall -

  • can be caused by mid-latitude depressions (low air pressure systems that produce a lot of rain)
  • a depression happens when 2 air masses meet - one hot, one cold - cold air pushes the hot air up leading to its cooling, condensing and forming rain
  • heavy rains can lead to saturated soil - stops infiltration and increases surface runoff - water reaches channel quicker and causes flooding
• meteorological causes of flooding: extreme monsoon rainfall -

  • monsoon is a seasonal change in the direction of the prevailing winds as the inter tropical convergence zone moves northwards
  • change results in wet and dry seasons in subtropical areas that are close to oceans - means that India and south east asia are at particular risk
  • summer monsoon (April-september) leads to extreme rainfall in India and south East Asia - during July 2015 heavy monsoon rain resulted in 103 deaths in Myanmar
• meteorological causes of flooding: snowmelt -

  • when temperatures increase after winter, snow and ice in higher latitudes or altitudes melt
  • particularly evident in mountain environments and the increase in water results in increased surface runoff and consequential flash floods
• meteorological causes of flooding: ENSO La Niña -

  • change in weather pattern across south pacific ocean as part of the ENSO cycles
  • la nina events exaggerate the normal weather patterns - La Niña years bring warm weather and low air pressure to Australasia so the rainfall increases as does risk of flooding
• environmental impacts of flooding: soils -

  • when flooding takes place sediment from places (eg banks and beds of the river) are eroded
  • this sediment can block sections of a river - eg underground waterworks
  • flooding can also lead to soil erosion of fertile soil in places such as the amazon
• environmental impacts of flooding: ecosystems -

  • flooding can destroy plants so they are damaged beyond use or are uprooted and broken into pieces in the river channel
  • when agricultural land is flooded a farmers harvest may be destroyed and they will need to completely restart
  • if plants, agriculture or habitats are damaged by flooding, the animals that are dependent on them for food and shelter are at risk - animals have to compete for limited resources or migrate to other ecosystems resulting in a decline in some species
• socio economic impacts of flooding: economic activity -

  • many businesses close while transport and infrastructures such as roads and bridges can be damaged
  • businesses owners lose productivity and income when workers can't get into work
  • shops that are damaged may lose their stock
  • insurance companies often pay out to those who have suffered from the flood - 2015 cumbrian floods insurance companies predicted the total costs would reach £500 million - local economy and businesses lost £200 m
• socio economic impacts of flooding: infrastructure -

  • floods can lead to long term or temporary inability to use infrastructures (eg roads, railways + bridges) - 2015 cumbria floods damaged 100 bridges with a huge impact on communities
  • 2015 cumbria floods - road and rail travel was suspended because of the network damages
• socio economic impacts of flooding: settlement -

  • 2015 Cumbria floods - 42,000 homes were without power around Lancaster because of a flooded power station being shut off
  • 5,00 homes flooded within the 3 days of rainfall
  • damages to homes was a total of £150m
• climate change effects inputs and outputs: trends in precipitation -

  • changes include increased precipitation in some regions which results in flooding or change in ecosystems
  • likelihood of tropical storms increases as sea levels rise and sea surface temperatures increase - higher levels of rainfall mean that tropical regions near coastline are at risk of higher precipitation rates and flood risk
  • can reduce precipitation in regions that are used to having high rainfall
• climate change effects inputs and outputs: trends in evaporation -

  • areas that see an increase in temperature from climate change can lead to evaporation happening with greater ease
  • contrastingly areas that see a decrease in temperature may see a reducing in evaporation
  • if temperatures decrease to below freezing water may remain frozen and so be stored as ice
• climate change affects stores and flows: slow and glaciers -

  • lead to increase in average global temperatures - leading to a reduction in ice-forming seasons
  • 2018 saw smallest amount of winter arctic ice since the 1960s
  • sea ice is not forming to the same extent and current sea ice is breaking off into large icebergs
• climate change affects stores and flows: reservoirs and lakes -

  • not being recharged as they previously were because of decreases in rainfall and higher temperatures in some areas
  • lake chad and Uzbekistan Aral Sea are drying up with devastating impacts on the ecosystem and the local residents - chad, Cameroon, niger and Nigeria all rely on lake chad as a water source
  • lake chad was once the 3rd largest source of freshwater in Africa but is now 1/20th of the size it was 40 years ago
• climate change affects stores and flows: permafrost -

  • permafrost = frozen ground near the poles in high latitude regions - can hold water in the form of ice
  • in summer if soil temperatures increase above freezing permafrost can thaw and ice within can melt - thawing leads to percolation and through flow until water has left the ecosystem
  • climate change often leads to a rise in temperature in permafrost regions - so as soil temperatures increase so will the amount of permafrost lost
• climate change affects stores and flows: soils -

  • different soils in different climates will be affected by global warming differently, depending on the weather extremes
  • generally soil moisture levels will decrease as less water will infiltrate the soil in droughts and in periods of intense rainfall because of the high runoff rates
• impacts of climate change: El Niño southern oscillation -

  • El Niño southern oscillation cycles produce uncertainty for weather patterns as conditions change in different years
  • El Niño sees winds decline and reverse direction - warm water moves towards South America - low air pressure increases rainfall and flood risk rises
  • contrastingly ocean temperatures drop in Australasia meaning higher air pressure, less rainfall and increased drought risk
  • la ninan events exaggerate normal weather and increase drought risk in south America and flood risk in Australasia
• impacts of climate change: increased uncertainty -

  • climate change increases the uncertainty with weather patterns across the work - resulting in higher or lower precipitation that leads to either drought and floods
  • sea level rise and warmer sea surface temperatures increase the chance of tropical storms and the floods associated with them
• impacts of climate change: drought risk projections -

  • areas that are at risk for future drought are: USA, Central America and the mediterranean - all around similar latitude - see a reduction in rainwater
  • southern mediterranean countries (eg Spain and Greece) - particularly at risk from drought because of their relatively high populations and reliance on tourism industry
  • countries seeing a reduction in drought risk: northern Alaska, asian countries , countries surrounding Indian Ocean
• impacts of climate change: flood risk projections -

  • south east Asia (eg India and Bangladesh) - seeing increase in likelihood of flooding
  • 70% of Bangladesh is on a floodplain and majority of nation is only 1m above sea level
  • climate change likely to cause Himalayan glacial meltwater to increase and flood the rivers - sea level rise and the increased likelihood of tropical storms (cyclones) means Bangladesh is increasingly at risk from flooding
• climate change impacts in The Sahel -

  • arid region bordering to the south of the Sahara desert