A LEVEL ENVIRONMENTAL SCIENCE: The Hydrosphere
Terms in this set (57)
locations of water on earth
atmosphere = 0.27%
land = 2.8%
oceans = 97%
hydrosphere closed system
water exists in a closed system in the hydrosphere; no inputs or outputs of matter (water), but does have inputs and outputs of energy.
water stores on earth
ice, lakes & rivers, ground water
water store residence times
oceans = 3600 years
polar ice and glaciers = 15,000 years
groundwater (aquifers) = up to 10,000 years
lakes = 2 weeks - 10 years
rivers = 10 days - 2 weeks
soils = 2-50 years
atmosphere = 10 days
biosphere = 2 - 50 weeks
factors influencing availability of above ground water stores
- presence of rivers
30% of all freshwater is stored in rocks deep below the ground surface, forming large underground reservoirs called aquifers.
most commonly form in chalk and sandstone as they are porous and permeable.
condensation of atmospheric water vapour that reaches the earth's surface in any liquid or solid
when precipitation does not reach the ground because it lands on vegetation
surface water that enters the ground between soil or rock particles
the sideways movement of water in the ground
the movement of water between particles of soil or rock
movement of water through the pore spaces and fissures in permeable rock
abstractive uses of water
removing water from system
15% of global use is
15% of global use is
30% of global use is
domestic = washing, drinking, etc
industrial = cooling power stations, chemical industry, etc
agricultural = irrigation
water quality requirements: turbidity
- suspended solids must be removed
- measured in TSS mg1-1 (Total Suspended Solids)
water quality requirements: pH
- if water is too acidic it can damage copper pipes
- too high or low pH can make water taste unpleasant
- ideal pH 6.5 - 8.5
water quality requirements: calcium content
- dissolved calcium ions make water 'harder', which is good for health and can help reduce tooth decay, osteoporosis, heart disease
- reacts with soap to produce scum
- reacts with hot water to produce solid limescale
water quality requirements: pesticide concentration
- pesticides are toxic, all should be removed from water
water quality requirements: heavy metal concentration
- heavy metals such as lead and mercury are neurotoxins so will damage the nervous system
- low concentrations won't cause any damage
water quality requirements: dissolved O2
- low dissolved oxygen levels can make water smell like rotten eggs (hydrogen sulphide)
- some toxic metals are more soluble in water with a low dissolved oxygen content
water quality requirements: chlorine retention
- chlorine is added to water to keep it sterile
- chlorine concentration may be reduced if other materials in the water react with it so more may need to be added
water quality requirements: e. coli abundance
- e. coli is always present if sewage has contaminated water
- 'coliform count' is a measure of number of e. coli bacteria present per litre of water
- potable (drinking) water should have a coliform count of 0
quality requirements of potable water for public supply
water looks, smells, and tastes good and contains no hazardous chemicals
quality requirements for spray irrigation water
low turbidity and no toxins, e.g. heavy metals
quality requirements of power station condenser water
no gross solids
quality requirements of power station boiler steam water
absolutely pure water
quality requirements of textile washing water
'soft' water with low dissolved calcium content
non-abstractive uses of water
use the water where it is found or nearby and do not take it away or move it to another water body or catchment area, e.g. energy
kinetic energy of moving river water is used to generate electricity
a dam is usually built to hold back a reservoir, so the river flow is altered but the water is not removed
three gorge dam, china
- built between 1994 and 2009.
- built on Yangtze river.
- 2km long, 185m tall.
- generates 22 500 megawatts.
- endangers Yangtze river dolphin due to ecosystem change.
- fed by Syr Dar'ya river (north) and Amu Dar'ya river (south).
- SD is 3000 km long
- AD is 2700 km long
- high salinity due to high evaporation leaving salt crystals behind.
- cotton crops along river - it is very polluted.
- when USSR built on river, the used poor materials - 70% of water was wasted.
results of over-abstraction from the aral sea
- water polluted and saline so less fish.
- climate became colder due to exposed sea bed.
- plants and animals died or moved away as they couldn't find enough food.
- halophytes and xerophytes have replaced the natural vegetation.
- 6650 km long
- 2830 km of discharge
- made up of blue and white nile
- Egypt owns 66% of the river
- sudan uses lots of the water for intensive farming and also to sell to other countries
- nile delta is used to plant cotton
- grand renaissance dam is built on the nile
- lake mead created by hoover dam
- Nevada uses 2% of water from river
- las vegas, los angeles, san diego, phoenix, and Tucson all rely on the river
- 10% of water diverted and taken to Arizona by canals, which have high rates of evaporation (waste).
water use in arizona
- 226 624 ha for irrigation from Colorado river.
- crops include cotton, fruits, and vegetables.
water use in california
- 364 217 ha used for irrigation from Colorado river.
- crops include fruits, vegetables, wheat, and grass.
water use in nevada
- water for irrigation is all ground water.
- allocated 370 000 000 ha from Colorado river.
- crops include fruit, vegetables, and grains.
layers of permeable rock, such as sandstone and limestone, containing significant quantities of water.
subsurface water. permanently saturated zone within solid rocks and sediments known as the phreatic zone where nearly all pore spaces are filled with water.
97% of total available freshwater is underground.
significant aquifers around the world
- below the sahara
- below the ganges (asia)
- below the indus (asia)
- below the hwang he plains (eastern china); supplies water for over 160 million people
aquifers bound both above and below impermeable rocks. creates pressure on water so it rises so it isn't sunk into the aquifer.
salt water incursion
makes water brackish
salts dissolve from the soil accumulate at the soil surface and are deposited on the ground e.g. Aral sea countries (Uzbekistan and Kazakhstan)
process of removing undesirable chemical and biological contaminants from raw water.
forces responsible for keeping the particles apart after they contact are reduced
brings the colloidal particles together and they form large aggregates called floc.
water remains static to allow suspended solids, such as silt, to settle.
meshes used to remove vegetation and litter
bubbles used to aerate and ensure high dissolved O2 content and remove dissolved metals.
flocculants mixed quickly with the water then passed into clarifier tank where particles are allowed to settle.
filters used to remove suspended solids and bacteria. usually consist of sand and gravel.
activated carbon treatment
particles of activated carbon remove organic chemicals e.g. pesticides which absorb into carbon particles.
chlorine, ozone, and UV light are used to sterilise water and kill pathogens.
sterilisation and chlorine can make water too acidic. crushed lime reduces this.
toxic ions e.g. lead, mercury, and arsenic can be removed using ion exchange resins. toxic ions absorb onto polymer beads or particles of zeolite.
also used to remove calcium and magnesium ions to produce 'soft' water.
- energy-intensive and expensive.
- only used where there are inadequate freshwater supplies where seawater is available.
- saline water is filtered at a very high pressure through the partially permeable membranes of small polyamide tubes.
- freshwater at the end is about half the volume of the original volume.
- lots of energy is needed so desalinating sea water is very expensive.
water is boiled by heating or reducing the pressure. the steam that is produced is condensed and collected.