P1 - Hydrological Cycle Flashcards
What are the meteorological causes of flooding?
Lots of flooding in the UK is the result of mid-lattitude depressions forming from low air pressure.
These usually bring showers on the warm front and rain on the cold front.
When rain is prolonged, the ground becomes saturated which causes more surface run-off
once the channel capacity is exceeded, water will break the banks and flow onto the floodplain
What are the physical causes of flooding?
- Flash floods
- Monsoons
- Rock type
- Soil saturation
- Tributaries
- Slope
- Snowmelt
What is flash flooding?
a flood with an exceptionally short lag time- often minutes or hours
What is groundwater flooding?
flooding that occurs after the ground has become saturated from prolonged heavy rainfall
What is surface water flooding?
flooding that occurs when intense rainfall has insufficent time to infiltrate the soil, so flows overland
What is residence time?
the amount of time a particle stays in a store
What is flow rate?
speed at which a particle moves from one store to another
CASE STUDY
What are some key fact of the 2015 Storm Desmond?
- 6ft of water
- Roads washed away and buldings submerged
- Army dropped off water and nearby villiages bought food
- Flood defences were built after the 2009 flood but the didnt work
CASE STUDY
What are some of the social consequences of Storm Desmond?
- 5200 homes flooded
- 20,000 people had to live in temporary accomodation
- Local services were forced to close
CASE STUDY
What are some of the environmental consequences of Storm Desmond?
- Rivers polluted with sewage
- Many riverbanks were eroded, adding to future flood risks
CASE STUDY
What are some of the economic consequences of Storm Desmond?
- The cost of the damage was £450m
- Insurance claims by flooding across the UK were £6bn in 2015
What are the human causes of flooding?
- Channel straightening
- Building on floodplains
- Impermeable ground
- Dams built to supply towns with water
- Streams channeled into culverts to aid rapid drainage of farmland
- Grazing animals trample soil
- Plouging compacts soil
- Dredging rivers
- Deforestation
- Changing land use
CASE STUDY
What are some key facts of the Boscastle 2004 flood?
- Helicopters worked for 3hrs, rescuing 120 people
£250,000 in damage - River level had risen by 7ft in one hour
- The villiage was built on a floodplain
- 2 million tonnes of water flowed through
- Saturation of bedrock from previous rain resulted in the sandstone behaving as if it was impermeable
What is a drought?
An extended period- a season, a year or several years- of deficient rainfall relative to the statistical malti-year average
What is a meteorological drought?
Happens where long-term precipitation is lower than normal. It changes for different regions as it is affected by the atmspheric conditions
What is an agricultural drought?
Happens when there is not enough soil moisture to allow enough crops to grow. It is caused by precipotation shortages, changes in rates of evapotranspiration and reduced groundwater levels
What is a hydrological drought?
Happens when the amount of surface and surface water is defficient. It is caused by a lack of precipitation and usually occurs after meteorological and agricultural drought
What is a socio-economic drought?
Occurs when water demand outstrips the water avaliability. This could be caused by a lock of precipitation or by human overuse of sources of water
What is the best indicator of drought and how does it work?
Palmer drought severity index. The higher the number the less severe it is
What is ecosystem resilience?
The ability of an ecosystem to respond to a disruption of normal function and recover quickly
CASE STUDY: California (drought)
What are the human contributions of drought?
- Population of 40 million meaning that there are human pressures on water supplies
- Climate change
- Huge industry of agriculture meaning that there is high demand for irrigation
CASE STUDY: California (drought)
What are the physical contributions of drought?
- Has mountains which affect rainfall
- Towards the eastern border is the Arizonian Desert
CASE STUDY: California (drought)
What is the evidence for the drought?
- 2007- Californian fires were due to the Santa Ana winds blowing out from the Great Plains
- 2007- was set to become the driest year on record- only 25% average rainfall
CASE STUDY: Horn of Africa
What are the human contributions of drought?
- Deforestation
- Overgrazing
- Urbanisation
- Climate change
- Lack of disaster resilience
CASE STUDY: Horn of Africa
What are the physical contributions of drought?
Changing weather patterns
Lack of rainfall
CASE STUDY: Horn of Africa
What is the evidence for the drought?
- 5 years of low rainfall
- Population double in previous 30 years- expected to increase by 40% by 2059
- 85,000 people evacuated due to transport links
What are some of the causes of flooding?
- Long or heavy periods of rainfall
- Impermeable soil & rock
- Saturated soils
why are wetlands important ecosystems?
- Mitigate against flood risk
- Recharge aquifers
- High biological productivity
- Protect land from erosion
- Act like water filters
- Provide fish and fuelwood
Why are forests important ecosystems?
- Second largest store of carbon
- 2 billion people rely on forests for food, medicine, firewood, etc
- TRFs produce 28% of oxygen
- Provide food, shelter, and fuel
- Home to 80% of terrestrial biodiversity
What are the ways drought can affect wetlands?
- water availability- water table lowers and dries out wetlands
- water quality- water=more concentrated=decreases water quality
- Habitat loss- species forced to migrate
- Altered nutrient cycling- reduction in water flow=lower exchange of nutrients with surrounding areas
What are the ways that drought can affect forests?
- Reduced soil moisture- plants cant obtain water
- Increased fire risk- dry conditions=easier for forest fires to start and spread
- Altered tree growth- slows down
- Changing in species composition- species cannot adapt and could face extinction
- Impact on wildlife- species may experience a change in distribution
High pressure
when air sinks- has drier conditions
Low pressure
when air rises- has wetter conditions
What is a ‘normal year’?
there are droughts in South America and floods in Australia
What is a ‘La Nina year’?
an enhanced ‘normal year’
What is an ‘El Nino year’?
there are floods in South America and droughts in Australia
What percentage of the earth is water?
70%
Transpiration
Evaporation that occurs off of leaves
Percolation
Waters moving down due to gravity through rocks beneath (slowly)
Surface run off
Water flowing along an impermeable surface
Absorption
Water absorbed by plants and vegetation
What drives the water cycle?
-Solar input
-Gravitational forces
What is the importance of solar input in the water cycle?
- solar energy drives the cycle by evaporating water
- Latent heating=the energy required to change a substance to a higher state of matter. This same energy is released from the substance when the change of state is reversed
What is the importance of gravitational force in the water cycle?
- precipitation
- infiltration
- percolation
- surface run off
- on the land, gravitational potential energy is converted into kinetic energy as the water moves through the system by interception, surface run off, etc
Blue water
Water that is stored in rivers, streams, lakes, and groundwater in liquid form (visible)
Green water
Water stored in the soil and vegetation (invisible)
What type of system in the hydrological cycle?
Closed system
What type of system is a drainage basin?
Open system- it has inputs, transfers, stored and outputs
What is needed for precipitation formation?
- water vapour provided by evaporation and evapo-transpiration
- air cooled to attraction point with relative humidity at 100%
- condensation of nuclei to facilitate the growth of droplets in clouds
- temperature below dew point
Relief rainfall
- warm air rises and cools
- important to create ecosystems
- Moisture comes from the ocean
- Mountains do not allow rain clouds to pass over as the altitude it too high
- The cloud rains on one side of the mountain
- When it reaches the other side of the mountain it doesn’t rain that much
Convectional rainfall
- air is lifted and cooled
- clouds are formed which leads to rain
- happens in low pressure areas
Frontal rainfall
- boundary between the cold and warm fronts
- water vapour in warm air is condensed and then rains due to the cold air
- warm air wedges into the cold air
- leading front- warm front- warm air behind it
- second front- cold front- cold air behind it
How can precipitation affect the drainage basin?
- amount of precipitation
- types of precipitation
- seasons
Physical factors that can affect the drainage basin
- geology
- vegetation
- climate
- soils
Human factors that will affect the drainage basin
- deforestation/afforestation
- creation of reservoirs and other large surface storage areas
- changing land use (i.e. forests to farming)
What are the physical factors that can impact infiltration?
- soil porosity
- slope angle
- vegetation cover
- soil oisture
- duration of rainfall
What are the human factors within a adrainage basin?
- dams- control the amount of water that goes through. They can affect a drainage basin as they slow channel flo, change biodiversity, and increase the amount of time that the river is a store
- agriculture/farming- compact soil=harder to infiltrate so there will be more surface run-off
- deforestation- less interception so the soil will be saturated faster as infiltration happens quicker so there is more surface run off
- cattle farming- cows compact soil, eat vegetation meaning that there is less interception and absorption
Water budget
the balance between precipitation, evaporation and run off
Water balance equation
drainage basin discharge = precipitation - evaporation +/- run off
Evapotranspiration
Combined effect of evaporation and transpiration. Very important as it can remove 100% of annual precipitation in arid and semi-arid areas
Potential evapotranspiration
The amount of water lost if there was constant/unlimited supply of water in the soil
Soil moisture recharge
When precipitation is greater than evapotranspiration the pores of the soil are refilled with water
Soil moisture surplus
When the soil becomes saturated, excess water will run over the surface as surface run off
Soil moisture utilisation
When evapotranspiration is greater than precipitation, there is a reduction in the amount of water stored with the soil. The amounted water stored in the soil is also being reduced because some of the water is being transferred as throughflow to the river.
Soil moisture deficit
Eventually all the avaliable water stored in the soil will have been used up
River regime
the annual variation in discharge measured in cumecs
Water scarcity
An imbalance between demand and supply
physical scarcity
Insufficient water to meet demand
Physical factors that impact infiltration
- soil porosity
- duration of rainfall
- soil moisture
- vegetation cover
- slope angle
What are the human factors that can affect inputs, flows and outputs in a drainage basin?
- Dams- control the amount of water that goes through
- Agricultur/farming- compacts soil, increases vegetation and levels of interception
- Deforestation- decreases absorption, less compact soil and a decrease in interception
- Cattle farming- cows compact soil and eat vegetation so there is less interception
Short term and long term
What are the physical causes of drought?
- High pressure zones- regions where the atmospheric pressure at the surface of the planet is greater than its surrounding environent
- Blocking highs- any high (or anticyclone) that remains nearly statonary or moves slowly, so that it effectively blocks the ovement of igratory cyclones across its latitudes
- Cold ocean currents- ocean cooling leads to a high pressure system that leads to cloudless skies
Jet stream
Movement of winds in the upper atmosphere
True or False:
The average winter temps by the Yukon river are -3 to -40 degrees C and summer temps are between 5 and 10 degrees C
False
Winter temps= -5 to -35
Summer temps= 8 to 15
What is the vegetation in the lower course of the Indus river?
Marshy jungle
How many weeks within June and July does snowmelt occur by the Yukon river?
2-3
What is the source for the Indus river?
Tibetan Plateau
What is the source of the Yukon river?
British Columbia
How big is the Indus drainage basin in km2?
888,000km2
How big is the Yukon drainage basin in km2?
832,000km2
Economic scarcity
People can’t afford water, even when it’s avaliable
Water insecurity
Where present and future supplies cannot be guarenteed
Measured in m3/capita
How much water do you need to have to be seen as water secure?
above 17000m3/capita
Measured in m3/capita
How much water do you need to have to be seen as having water stress?
Below 1700m3/capita and above 1000m3/capita
Measured in m3/capita
How much water do you need to have to be seen as water scarce?
below 1000m3/capita
How many billion people lack clean drinking water?
1.8
What percentage of the world’s river and lakes are badly polluted?
50%
What percentage of the world’s pop. consumes 85% of its water?
12%
Physical causes of water inscurity
- Low lying areas- have poor water quality due to the land being used for farming- chemicals contaminate water
- Topography- promotes increased precipirtation and rapid run-off
- Drainage basins
- Geology- controls distribution of aquifiers
- Global atmospheric circulation
- ENSO systems
CASE STUDY:
Human causes of Malta’s water scarcity
Too much water is being withdrawn from boreholes- both illegally and legally
CASE STUDY:
Physical causes of Malta’s water scarcity
- Seawater is steadily making the groundwater more saline and less viable for domestic and agricultural use
- Dry conditions
CASE STUDY:
Solutions of Malta’s water scarcity
- Extensive leak repair program
- Any water management plan in Malta will have to protect water supplies for the precious natual ecosystems in the island
- Two wastewater reuse programs, one agricultural and one domestic
- Rainwater harvesting
- De-salination
Human causes of water scarcity
- increased pop = more individuals consuming water = higher demand
- more disposable income = lower awareness and higher wastage = higher demand
- increased agriculture = higher irrigation = higher demand
- increased use of appliances = increased household demand for water
What is saltwater encroachment and name two examples of where this is happening?
Where the saline (salt) water passes through the brine into the fresh water. This water is them pumped out but is not suitable for human consumption which causes water stress
Examples:
* Florida
* Southampton
CASE STUDY
What percentage of th waterways in New Zealand are unsafe to swim in?
60%
CASE STUDY
Wht is the main cause of water pollution in New Zealand
Cows
CASE STUDY
What is the number of cattle in New Zealand compared to the number of people?
Cattle = 6.6m
People = 4.7m
CASE STUDY
What are the problems caused by bovine urine?
- nitrogen can cause toxic algae to grow when it omes into contact with water
- groundwater contains too much nitrogen so is unsafe to drink
- exepected mothers have to test tap water as it could cause blue baby syndrome
CASE STUDY
What are the problems caused by cow dung?
- Contains E-coli
- New Zealanders are 3x more likely than Australians ad Canadians to fall ill from Campylobacter
It is a fraction
CASE STUDY
How many native freshwater fish are there that are in danger in New Zealand?
3/4
CASE STUDY
How is New Zealand tackling the problem of water quality?
- fence off rivers
- Remove animals from muddy fields in the winter
- make 90% of the rivers swimable by 2040
