The Physical Environment (AS); The Hydrosphere (Complete)

Total amount of water on the planet

It is renewable & essential for all living organisms. Human Society has only been able to develop easily where water is available

Agriculture - 70%, eg. Irrigation Industry- 20% eg. Cooling, heating, washing, solvent Domestic uses- 8% eg. Flushing toilets, washing clothes/dishes, hygiene

• Increase in population • increase in per-capita use w/ increased affluence In the poorest communities, there is no piped supply and so water is often limited to the amount that can be carried. As piped water becomes more available & people more affluent, modern appliances are more common. • increased irrigation of farmland As commercial agriculture expands, increased income allows ↑ irrigation schemes, the water of which may be pumped from aquifers/rivers. Irrigation now uses more water then all human uses combined. • industrialisation Industries have varying water requirements. Heavy industry like chemical & steel use much more water than lighter manufacturing industries

Oceans- 97%, residence up to 4000 years Land ice- 2%, residence 20-100 years Groundwater- 0.7%, 100-10,000 years Lakes,rivers- 0.01%, 2 months-100 years Soil moisture- 0.005%, 2 months Atmosphere- 0.001%, 10 days Living organisms- 0.00004%, 1 week

Some reservoirs are abundant but are transferred slowly, like groundwater Others have a small total quantity but are transferred quickly, like atmospheric water

Volume of water in reservoir/mean transfer time

-Affect the transfer rates in the cycle, upsetting existing dynamic equilibria -This changes amount of water in different reservoirs on global/regional/local scales -The rate of change can vary, eg- some glaciers are shrinking rapidly while others are slowly changing -The extent and direction of the changes may differ in different areas, eg- one area declining rainfall another increases

-On water quality, through the release of pollutants -Their impact on the hydrological cycle tends to be local & most obvious where large urban centres have developed in areas w/ restricted water supply

-Vegetation intercepts rainfall which may evaporate before reaching ground -Trees also return a lot of water from soil to atmosphere by transpiration -The loss of trees can cause a significant reduction in precipitation in downwind areas as more water infiltrates ground/runs off into rivers

-Soil can be compacted by use of heavy farm machinery/livestock trampling -Water doesn’t infiltrate easily into compacted soil so soil moisture levels drop, runoff increase -Crop irrigation increase evaporation rates -Loss off soil biota like worms reduces infiltration, increases surface runoff & reduce water retention by soil

-Urban areas often have impermeable surfaces like concrete,tarmac -This reduces infiltration while increasing rate of runoff -Rapid runoff from large urban areas can increase river flooding downstream

-Higher global temperatures affect rates of melting, evaporation, condensation & wind patterns ^These combined with to alter the type, amount, timing & location of precipitation -More rapid melting of snow & ice—> caused by warming associated w/ global climate change -Snow fall in cold weather & later melting in warm weather reduces extremes in river flow, so loss of ice may increase flooding after heavy rain & low river flow during periods of low rainfall

-Some river water abstraction= little impact on river as used water is cleaned, returned to river -But, rivers have often been used to carry away wastes -Some abstractive uses do not return water to river—> reduces downstream flow, eg agricultural irrigation

Habitat change- flooding reservoir destroys previous habitats but also creates new, valuable ones. Wetlands= uncommon habitats in most regions, so reservoir may be more valuable than what was lost Wildlife change- dam + reservoir act as barrier to wildlife that migrate along river, like salmon. Free movement along river= important part of recolonising areas that have become vacant in bad years, dam may prevent this

-Reservoirs may be used in 2 ways -Water may be used to regulate river flow, holding water back in times of surplus to ensure adequate river flow in times of shortage—> reduces risk of flooding downstream + periods of lower flow, important for species like turtles who lay eggs in sandbanks -Rapid flow period= important to wash away sediments from gravel river beds where salmon & trouts lay eggs -Changes in river fluctuations can change river erosion & sedimentation, so also development of meanders

-Sediments carried into reservoir will settle there + not be carried further downstream -In past, they may have been important to fertilise floodplain downstream -May also have built up river banks & coastlines & counteracted erosion

-Large body of water may change local climate -High heat capacity of water helps reduce temp fluctuations—> warmer in winter, cooler in summer -Water provides less friction than land—> windspeeds higher -Greater evaporation from reservoir surface may increase humidity, cloud cover & precipitation downwind of reservoir

-Syr Darya + Amu Darya rivers flow through Central Asia to Aral Sea (formerly 4th largest lake) -Since 1960s, huge irrigation schemes in part of Soviet Union (now part of Kazakhstan) used river water to irrigate cotton & rice crops -River flow—> Aral Sea declined, sometimes to 0. Area of lake reduced by 90% & pollution by pesticides, fertilisers, and industrial waste caused serious problems. -Still disagreements betw. countries sharing river (Kazakhstan, Uzbekistan, Turkmenistan, Tajikistan, Krygystan) -Abstraction for irrigation reduces downstream flow. Flow through HEP dams in summer may be reduced to store water for winter gen but this reduces availability of summer irrigation water downstream

-Longest river in world; flows through 10 countries incl Egypt, Sudan and Ethiopia. -Long disagreement w/ countries over direct water abstraction for irrigation & construction of dams to regulate flow, give water, and generate electricity -As populations grow + these countries develop economically, demand for water may increase and risk of conflict may grow.

-Tibet= formally independent, now part of China since 1950 -Tibetan plateau—> source of many of Asia’s major rivers, w/ more than 1500m people depending on water from the rivers Indus, Ganges, Yellow rivers, Mekong and more. -Growing populations + increased demand for agriculture, industry may lead to water shortages & conflict between countries -Issue of water shortages may be made worse by seasonal fluctuations in river flow due to climate change -Melting of glaciers in Himalayas maintain river flow in dry seasons but receding glaciers may produce less reliable river flow in future

Colorado; USA, Mexico Murray-Darling; Australia Yellow River; China Indus; Pakistan Euphrates & Tigris; Turkey, Iraq, Syria Jordan; Isreal, Lebanon, Jordan, Palestine

-Often reduces downstream flow -Affects river and lake it feeds, some rivers completely cease to flow

-Bodies of rock, holds water which is exploited as a resource -For a rock to form an aquifer must have certain features