The Hydrological Cycle Flashcards
What is residence time?
How long a particular water molecule spends in a particular store.
E.g. long residents time may be ice and short residence time may be living things
What is transfer rate?
The amount of time it takes a water molecule to be transferred from one store to another.
How do you work out residence time?
Volume (km^3) / transfer rate (km^3 year^-1)
Name all the water reserves
Oceans
Land ice
Groundwater
Lakes and rivers
Soil moisture
Atmosphere
Living organisms
What percentage of the hydrosphere is oceans?
97%
What percentage of the hydrosphere is land ice?
2%
What percentage of the hydrosphere is groundwater?
0.7%
What percentage of the hydrosphere is lakes and rivers?
0.01%
What percentage of the hydrosphere is soil moisture?
0.005%
What percentage of the hydrosphere is the atmosphere?
0.001%
What percentage of the hydrosphere is living organisms?
0.00004%
Which reservoir has the longest water residence time?
Groundwater
Which reservoir has the shortest water residence time?
Living organisms
What is evaporation?
The process by which a liquid turns into a gas
What is precipitation?
Any liquid or frozen water that forms in the atmosphere and falls to the earth.
What is transpiration?
A process that involves the loss of water vapour through the stomata of plants
What is infiltration?
The flow of water from above ground into the subsurface.
What is interception?
The part of the rainfall that is intercepted by the Earths surface and which subsequently evaporates.
What is percolation?
The movement of water through the soil itself
What is runoff?
Occurs when there is more water than land can absorb
What is surface flow?
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What is groundwater flow?
Gravity and pressure move water downwards and sideways through spaces between rocks. Eventually merges back to land surface.
What is abstraction?
The process of taking or extracting water from a natural source (rivers, lakes, groundwater aquifers, etc.) for various uses, from drinking to irrigation, treatment, and industrial applications.
How does building dams affect the water cycle?
Holds water, reducing percolation and infiltration
Decreased groundwater and increased surface water
How does urbanisation affect the water cycle?
Increased interception of water
Increased surface flow and runoff due to impermeable surfaces such as concrete and tarmac
How does deforestation affect the water cycle?
Increased surface flow and runoff due to decreased interception
Decreased transpiration rate
How does combustion of fossil fuels affect the water cycle?
Increased greenhouse gases leads to increased temperatures and water in the ocean
This leads to increased evaporation and increased precipitation
How does food production (agriculture) affect the water cycle?
Abstraction of water from natural stores to be used in agriculture
How does mining affect the water cycle?
If mining is below natural water table, you must decrease ground water by pumping it into rivers and other bodies of water
How does consumption affect the water cycle?
Collect water in reservoirs
Domestic uses
Drinking
How do canals affect the water cycle?
Suez Canal - man made, changed transport of goods, sea water
Block in order to increase and decrease water levels
How does afforestation affect the water cycle?
Decreases surface flow and runoff due to increased interception
Increased transpiration
How do aquifers affect the water cycle?
Abstraction of water
What are the major factors that may cause demand for water to change?
Change in industry over time
Increase in population
Change in affluence
Increased food production/agriculture
What is the most water used for in the UK?
Energy industry (eg used for cooling)
Define water footprint
An environmental indicator that measures the volume of fresh water (in litres or cubic metres) used throughout the entire production chain of a consumer item or service.
Name and describe the exploitation of a river
The River Nile
Exploited by Egypt downstream
Other countries upstream begin to use it for economic gains
Supports agriculture and fishing
Sediment at bottom polluted with heavy metals
Many people rely on it
Flow has dropped
Lake Victoria which supplies the Nile may dry up
Dam built
What is a reservoir and why do we build them?
A reservoir is an artificial lake where water is stored.
Reservoir water can be used to supply water to our homes and factories. Reservoirs are designed to store the rain that falls during the wetter parts of the year, so that there is a continuous supply of water for the drier periods.
Also a critical part of flood risk management
What are the advantages of reservoirs?
Flood management
New jobs
Reliable
Cheap water
New habitats
What are the disadvantages of reservoirs?
Lost dry habitats/changed habitat to fresh water habitat
Lost homes
Lost livelihoods
More water upstream and less water downstream
Sediment that contains nutrients settles upstream and not downstream
Acts as a migration barrier
Water has a high specific heat capacity (creates a microclimate - cooler in summer and water in winter) - could be an advantage
What are the environmental impacts of reservoirs?
Habitat change (still, deep body of water from flowing river/stream)
Wildlife/migration barrier (prevent breeding and growth)
Changes in river flow downstream of dams
Sedimentation (sediment drops as velocity of water decreases)
Reservoir microclimate - local abiotic factors (water has high latent heat)
What are the factors effecting reservoir location?
Topography (eg steep sided valley with exit with river/stream)
Geology (rock must be impermeable and strong with no seismic activity)
Catchment area (want a large catchment - area of land in which water flows to get to the desired area)
Water supply (eg high rainfall)
Pollution risk (wants to be low, upstream of any pollution source e.g. runoff from agricultural land)
Sedimentation (put reservoir in place where water is less turgid, reduce soil erosion/vegetation on banks
Infrastructure (need infrastructure e.g. roads)
Existing land use and land use conflicts (displacement of areas, agriculture and food production)
What is an estuarine barrage?
A dam that is built across the mouth of a river close to where it meets the sea
Easy way of holding the water back
Lots of transport (usually have a major port)
What is an aquifer?
A volume of rock that is saturated (rock is like a sponge) eg sandstone and chalk
What are the 3 main features that allow the formation of an aquifer?
Porosity
Permeability
Suitable geological structures
What is porosity?
Measure of the proportion of pore space between the grains that make up a rock
What is permeability?
Measure of the rate of movement of water from one pore space to the next
What are suitable geological structures for the formation of an aquifer?
Limestone, sandstone and chalk
Pours and permeable rock underlain by impermeable rock
What is an unconfined aquifer?
Where the rock is directly open at the surface of the ground and groundwater is directly recharged
What is an confined aquifer?
Where thick deposits overlay the aquifer and confine it from the Earth’s surface or other rocks
What is a artesian well?
A well that brings groundwater to the surface without pumping because it is under pressure within a body of rock known as an aquifer. (Confined aquifer)
What are the consequences of aquifer overuse?
Reduced supplies (deeper wells need to be build now)
Subsidence - land moves downwards
occurs when there is a loss of support below ground
This is due to water being removed from the ground/lack of water
Changes in surface hydrology (if water table lowers, some surface water features may be lost e.g. lakes and rivers …. Leading to loss of freshwater habitats)
Ecological impacts (water table lowers causing habitat loss)
Saltwater incursion (empty aquifers draw in water such as salt water which is a problem for domestic, agricultural and industrial use - deposits in pipes and machinery)
Salt will take a long time to leave (same with other pollutants too)
How can we monitor aquifer water levels and rates of depletion?
Boreholes
- use existing boreholes
- monitor water table
- if water in borehole increases then water in aquifer has increased
NASA - GRACE satellites
- takes gravity measurements around the earth
- if lower than expected gravity readings, there is less mass meaning less water
- continuous data that covers a large area
Where are the major aquifers in the UK?
The lowland of England
Usually chalk
Generally the south-east near London
London Basin - most important aquifer in the use
What is the most important/used/managed aquifer in the UK?
London Basin
What rock acts as the ground water reservoir in the London Basin?
Chalk
Which rock lies below the London Basin aquifer?
Clay
What is the London Basin aquifer water supply used for?
Domestic
Industrial
Agricultural
Brewery
What is meant be aquifer recharge?
Where water goes back into the ground via precipitation or other methods
Overexploitation of aquifers: North China Plain
Land subsidence, ground fissuring, seawater intrusion, lowering of saline water interference and pollution of deep ground water.
Explain how rainwater is harvested and used in modern/eco buildings
A whole house rainwater harvesting system involves piping rainwater from your down pipe to a storage tank and filtering it on the way to remove coarse material like leaves.
New ways of exploiting water
Estuary barrages
Desalination of water
Water from new rivers
Build new reservoirs
Exploit aquifers that we haven’t before
Pipe water to places that need it
Explain how aquifers are recharged artificially
We take areas with surplus water and pipe it directly into a depleted aquifer
How can reservoirs be used to regulate river flow?
In lots of areas, water availability is seasonal. That means river levels can fluctuate throughout the year.
Explain what is meant by the term inter basin transfer and give an example of where this happens.
The moving of water from a watershed with a surplus (donor basin) to a watershed suffering from a shortage (recipient basin).
North Wales (excess) to south-east London (shortage of water)
How can afforestation help with water supplies?
Reduces runoff
Increases groundwater stores
Increases infiltration
Keeps water in one location for longer
How can we reduce domestic, industrial and water consumption?
Water meters
Duel flush and low flush toilets
Less baths
Shorter showers
Grey water recycling
Drip irrigation
Xeriscaping
Why do we test for turbidity (Tiny suspended solid particles in the water)?
Public perception
Pathogens/bacteria could be attached
Light availability - problematic for photosynthesis
Why do we test for pH?
Range of tolerance
Strong acids/alkalis denature proteins
Why do we test for calcium content?
Limescale
Calcium deposits on machinery
Causes dishwaters and washing machines to break earlier
Why do we test for pesticide concentration?
Toxic
Liposoluble
Why do we test for heavy metal concentration?
Poisoning - problematic to nerves e.g. lead, lithium and cadmium
Why do we test for dissolved oxygen?
Aerobic aquatic organisms need oxygen
Why do we test for chlorine retention?
Don’t want chlorine to escape as gas (some is fine)
Why do we test for E.coli?
Indication of faecal matter
What is the water quality requirement for potable water for public water supply?
Looks, tastes and smells good and contains no hazardous material
If requirements not met:
Public complaint
Public health risk
What is the water quality requirement for spray irrigation?
Low turbidity. No toxins, eg heavy metals
If requirements not met:
Blockage of water supplies
Contaminated food
What is the water quality requirement for power station condenser water?
No gross solids
If requirements not met:
Pipe blockages
What is the water quality requirement for industrial boiler water?
Absolutely pure water
If requirements not met:
No minerals. They build up in the boiler.
What is the water quality requirement for textile washing?
Soft water with low dissolved calcium content
If requirement not met:
Build up of scum
Methods of fresh water treatment: screens
Water is passed through ‘grills’
Used to remove large objects
Methods of fresh water treatment: sedimentation
Leave water to stand in a large basin for an extended period of time
Let’s the suspended solids (floc particles) settle at the bottom as sludge
Floc particles are removed from the bottom of the basin and taken to landfill or a holding facility
Cleanest water at the top flows over weirs to the next stage
Methods of fresh water treatment: aeration
Pass O2 bubbles through water. This agitates the water.
Increasing dissolved O2 in water reduces anaerobic decay which would create bad smells.
Aeration provides oxygen to bacteria for treating and stabilizing the wastewater. Oxygen is needed by the bacteria to allow biodegradation to occur.
Methods of fresh water treatment: flocculation/coagulation
Coagulant is added (eg aluminium sulphate) and work to congeal the particle together in the water
Flocculations is when the solution is mixed (in mixing basins called flocculations basins) and forms floc particles
Makes it easier for removal
Methods of fresh water treatment: filtration
Water is passed through (fine to course) sand, solids are left behind in the sand.
Methods of fresh water treatment: activated carbon filters
Activated carbon particles have a large surface area (hundreds of tiny pores)
Removes tiny sediment and bacteria
Helps improve taste and odour
Methods of fresh water treatment: sterilisation
Add chlorine
- kills microorganisms
- residual chlorine levels remain in the tap water, killing contaminants
Add Ozone
- kills bacteria in the water as well as improving the taste and odour
- chemical must be used to remove ozone at the end
Pass water under UV light
- doesn’t kill bacteria but prevents it from reproducing
- not residual like chlorine
What are floc particles?
Coagulant and water solution mixed together forms floc particles
Methods of fresh water treatment: pH control
The addition of chlorine made decrease pH, so an alkaline may be added
Bubble through limestone
This helps pipe works
Methods of fresh water treatment: fluoridation
Not essential
Add Florine
Improves dental health
Methods of fresh water treatment: ion exchange
Add a chemical or polymer that attracts heavy metals eg lead and arsenic
To remove heavy metals from water
To remove calcium from hard water
Ion exchange in water treatment involves removing undesirable ionic contaminants from the water by exchanging them with another ionic substance.
Seawater Treatment: Reverse osmosis
- seawater unsuitable per most agricultural, industrial and domestic uses
- very abundant
- reverse osmosis forces seawater through a semi-permeable membrane at high pressure
- H2O molecules pass through salt molecules do not
- low/no salinity
- very high salinity water returned to see
- very energy intensive
- last option
Seawater Treatment: Distillation
- heat water - salt is left behind when water evaporates
- can make own distillation
Why is Kuwait the most dependent country on earth for water imports?
It suffers from severe water scarcity with a lack of readily available surface water.
Explain why chocolate has such a high water footprint.
The cocoa bean needs the most water for it’s growth of all plants.
Manufacturing
Explain why a typical USA citizen has such a high water footprint and give examples of water use.
Growing the food we eat, generating energy and manufacturing clothes and other goods increase US citizens water footprint.
Explain why Brazil has the highest renewable water resources in the world.
Brazil has highest freshwater resources in the world which is accounts for approximately 12% of the world’s freshwater resources.
What can abstracted water be used for?
Domestic uses e.g washing
Agricultural uses e.g watering crops
Industrial use e.g cars, steel and power stations
How is the London Basin recharged?
North London Artificial Recharge Scheme (NLARS) run by Thames Water; and the Wandle Artificial Recharge Scheme (WARS) operated by SES Water.
