The hydrosphere Flashcards
What do human activities do to the hydrosphere?
They can alter the rate of processes in the hydrological cycle which can lead to changes in the residence time and quantities in reservoirs of water.
How do you calculate residence time?
vol of water in reservoir/ mean transfer rate
Why is the global demand for water increasing?
Increased population
Increase in per-capita with increased affluence so more piped water, water appliances
Increased irrigation of farmland for growing populations
Industrialisation e.g. chemical and steel
What are the inputs for the hydrological cycle?
Precipitation
What are the outputs of the hydrological cycle?
Evaporation
Transpiration
What are the ways water moves to different reservoirs/ transfer processes?
Percolation
Ground water flow to the ocean
What drives the hydrological cycle?
Solar energy-evaporation etc
Gravitational potential energy- water moves through rocks to the ocean
How do you convert m3 to km3?
Divide by 1000
What is the residence time?
The average time a water molecule will spend in a reservoir
How does deforestation affect the hydrological cycle?
Vegetation intercepts rainfall which may evaporate before reaching the ground.
Trees return alot of water from the soil to atmosphere by transpiration.
How does agriculture affect the hydrological cycle?
Soil being compacted will reduce infiltration and increases runoff
Crop irrigation may increase evaporation
Loss of soil biota will reduce infiltration, increases run off and reduces water retention.
How does urban development affect the hydrological cycle?
Replacing impermeable surfaces like concrete with gravel/sand will increase infiltration and reduce runoff.
What water sources have been exploited unsustainably?
Aquifers and reservoirs
What was the main reason for the aral sea drying up?
Irrigation of cotton and rice crops using water from rivers that fed into the aral sea.
Pollution from pesticides and fertilisers
What is an aquifer?
An underground layer of water bearing rock
What are the features of rock suitable as an aquifer?
Good porosity so alot of space to hold water, limestone/chalk
Rock above should be permeable but rock underneath should not be, granite or clay.
How are aquifers recharged?
By rain, they are usually in dynamic equlibrium.
When does an aquifer become over exploited?
When human abstraction is greater than recharge.
What water is usually in ancient aquifers?
Saline water, so it causes soil salination, osmotic dehydration and then crop death if used for irrigation
What are the ecological impacts of over exploiting aquifers?
Plants die
Wetland habitats will decrease killing aquatic plants and animals
Affects inter-species relationships and food webs
What is salt water incursion?
When aquifers are exploited their water table lowers, it could become lower than the sea level causing seawater to flow in to replace what has been lost.
This makes the aquifer saline, water cannot be used in irrigation
What is subsidence?
Over exploitation of aquifers means less water is held in porous rock, the rocks therefore have less support and will become compacted by the weight of material above.
How can you measure aquifer depletion?
Checking the water table
Grace satellite/ gravity recovery and climate experiment: the orbit of this satellite is affected by gravity which is influenced by the mass of water in aquifers
Describe the ogollala aquifer and what the problems are
A high plains aquifer
Agriculture relies on this aquifer however it is being over exploited/ abstraction is greater than recharge.
The water in this aquifer is paleowater, so it was last recharged years ago
What are some methods china has implemented to conserve their water?
Growing crops with low water needs
low pressure irrigation pipes to reduce leaks
afforestation
charging for overconsumption of water
What are the environmental effects of reservoirs?
Construction of a dam/reservoir changes habitats, but creates wetlands.
Dam will act as a wildlife barrier to migrating wildlife, prevents recolonisation.
Sedimentation, no nutrients bought downstream
Changes the microclimate: large body of water and high SHC stops temp fluctuations. Greater evaporation so more precipitation.
How are river flow regimes used?
Used to regulate flow.
When flow is high/ in surplus water is held back to stop flooding.
When flow is low water is released
What are the features of a good reservoir?
Topography- narrow exit with a large deep basin
Geology- underneath rock must be impermeable, but also strong
Catchment area- area of high rainfall, or an area with a river that carries water to the reservoir
Low pollution risk
Why should a reservoir not be near a forest?
Dead organisms from the forest will decay in the water anaerobically releasing methane
What infrastructure has to be taken into account when building a reservoir?
Building the dam
Treatment of water
Pathways for machinery
Pipes to transport water
Workers
What is an estuary barrage?
A freshwater reservoir created by making a dam across an estuary
What are the problems with estuary barrages?
They change inter-tidal relationships
Create a problem for shipping
Water stored may be polluted
Why is seawater not used?
The desalination process is very expensive and energy intensive
What is artificial recharge?
Maintaining aquifers by using surplus water to recharge them.
Water is pumped into the aquifer or it is put into a lagoon where is can infiltrate
What are river-regulation reservoirs?
Used to regulate river flow
In low rainfall water can be released and in high rainfall water can be held back to reduce flooding
What is inter-basin transfer?
A pipe system to transfer water from areas of shortage
What are some methods used to conserve water?
Low water appliances
Xeriscaping
Drip irrigation
Recycling water/grey water being used to water crops
Water meters
Maintaining old pipes so no leaks
Controlling pollution so less water needs to be treated.
What is potable water?
Drinking water, has no has no pathogens
What does irrigation water have to be?
Not saline
Low toxins
Low sediments
What is the water treatment process in order?
Sedimentation
Screening
Aeration
Flocculation
Filtration
Activated carbon filter
Sterilisation
pH
fluoridation
ion exchange
What is screening?
Using mesh screens or metal bars to trap and remove large objects like plastic
What is aeration?
Using water sprays to aerate water and ensure a high dissolved O2 conc.
Makes metals become insoluble
What is flocculation?
Clay particles will not settle in sedimentation due to electrostatic charges causing them to repel.
The charges can be neutralised by adding alum/ aluminium sulfate.
What is filtration?
The removal of the remaining materials by letting it flow through sand/gravel
What is activated carbon filter?
Removes organic chemicals like pesticides by adsorption onto activated carbon
What is sterilisation?
Using chlorine, UV or ozone to kill pathogens
What is pH in the water treatment processs?
Using crushed lime to make conditions more alkaline because when using chlorine water will become acidic.
What is fluoridation?
Adding fluorides to improve dental health
What is ion exchange?
Toxins, like lead, iron and calcium removed.
They adsorb onto polymer beads this produces ‘soft’ water bc no calcium
What is reverse osmosis?
Sea water being filtered at high pressure through partially permeable membranes
V spenny process so not used often
What is distillation?
Water is boiled to produce steam, the steam is condensed to water vapour and collected
