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earths life support system 6 (case study: The Aral Sea (location -…
earths life support system 6
how is water used?
8% is used within households
22% is used within industry
70% is used for agriculture
surface extraction of water (e.g. taking water from rivers or lakes)
the two main sources of water are surface water from rivers, lakes and groundwater. in some countries the surface water is more abundant, in other arid areas, there is little and ground water must be used
Iceland
- mainly used surface water, little ground water due to high precipitation and low temperatures (little evaporation)
Central Australia
- groundwater used as there is little surface water (it evaporates any rain that falls and there is rain anyway)
the extraction of water in the UK
in the UK 80% of the water is from surface water and 20% is from groundwater
however, this varies depending on where you are in the country. the west of the UK is wetter so more surface water is used as there are more lakes
the east is drier and also more populated so more water is used, therefore the percentage of groundwater used is actually more like 50%
case study: The Aral Sea
location
- northern part of the sea lies in Kazakhstan and the souther part in Uzbekistan it is land-locked and 45 degrees north of the equator (latitude)
main rivers that feed in the sea
- the sry darya and the amu darya
state which regions/areas that these rivers originate from
- the hindu kush mountain range and the tian shan mountain range
extraction or abstraction
- 1960-1970: sea level fell by 20cm per year and in the 1980s the sea level fell by around 80-90 cm per year
impact the decline of the sea had on the local climate
sea bed was exposed and dried out. climate has become colder in winter and hotter in the summer (there is a large temperature range)
sea bed contained chemical residue, which were whipped in a toxic dust storm. rates of evaporation decrease meaning in summer there is less convectional rainfall causing a drought
UK case study - the River Kennet, South England
the river kennet has several large urban populations to provide domestic water for including swindon as well as local industry and agriculture
thames water abstract groundwater from the river kennet's drainage basin. this water is not returned to the river but used for domestic, agricultural and industrial use
aquitard: non-porous rock which restricts the flow of water from an aquifer
water table: the top of the saturated zone
confined aquifer: permeable rocks that hold large amounts of groundwater (sandstone) that is capped by impermeable rock
unconfined aquifer: permeable rocks that hold large amounts of groundwater that is NOT capped by impermeable rock
spring: when the groundwater meets the surface
recharge area: area where aquifer is unconfined and rain infiltrates
artesian basin: the artesian basin is one that is located at the centre of the synclinal structure
how does groundwater extraction impact of the flows and stores in the water cycle?
porous spaces are unoccupied meaning there is more infiltration
soils become dry and the rates of infiltration increase
rates of percolation increase as will the erosion of the bedrock.
if runoff rates decrease the river discharge will also decrease