- distribution of water globally is related to earth's climatic zones.
- regions near equator recive high levels of rainfall.
- tropical regions suffer recurring drought.
- rainfall varies with the seasons.
- e.g high mountains with snowpacks hold vast reserves of water which is released in late spring and summer.
- world rivers store vast amounts of water and transfer it across continents.
- e.g Amazon produces 20% of the river water entering the world's oceans.
- high temperature results in water loss by evaporation.
- impermeable rocks under river basin results in surface runoff.
- aquifers store vast quantities of water underground.
- uses 69% of world's 4,430.7 km3 a year freshwater supply.
- some forms of agriculture are less efficient than others.
- e.g kg of beef is 10 times more water costly than a kg of rice.
- 17% of area devoted to growing crops is irrigated.
- irrigatigation can be wasteful of water.
- poor management can leead to problems of evaporation and fertiliser pollution.
- uses 21% globally
- due to be a rapid rise in the next decade driven by large-scale industrialised countries such as india and china.
- HEP uses huge amounts of water but this is a more efficient user of water than agriculture.
- paper manufacturing however is the most extravagant users of water on the planet.
- uses 10% of global water supply
- varies country to country with developed countries using more and less developed using less
pressure on water supplies.
water stress- deamnd exceeds amount available during a certain period.
physical scarcity- shortages occur because demand exceeds supply.
economic scarcity- people simply cannot afford water, even when it is readily available.
- 4% of world's freshwater but 16% of it's pop.
- demand expected to exceed supply by 2020.
- urban demand expected to double industrial demand expected to triple.
- 8% of world's freshwater but 22% of it's pop.
- 2/3 chinese cities don't have enough water all year round
- uses irrigation to produce 70% of food in north and NE where the yellow river and major aquifers are running dry.
- engineering projects will son transfer water from the water rich south to north.
human impacts on water availability.
- sewage disposal in developing countries, expected to cause 135 million deaths due to diseases such as hepatitis, typhoid and cholera which are commonly found in polluted waters.
- chemical fertilizers used by farmers contaminate groundwater as well as rivers and water supplies.sewage and fertilizers add nutrients to the water and increase formation of algae downstream. the algae removes oxygen from water e.g along the shores of the gulf of mexico.
- 400 billion tonnes of industrial waste created per year, much of which is pumped into untreated rivers and oceans. heavy metals become concentrated in rivers, such as lead and mercury.
- big dams trap sediment in reservoirs, reduces floodplain fertility and the flow of nutrients from rivers into seas. this may damage fish stock and prevent beach formation which can result in more coastal erosion. sediments from dam construction can block gills of river fish and suffocate them.
- water being extracted from aquifers faster than it's being replaced. In arid area, rainfall can never recharge these underground stores.
- removal of freshwater from aquifers in coastal areas can upset balance of saline and fresh groundwater and result in salt water incursion & salinisation of wells, boreholes and wetlands.
Access to water.
Water insecurity means not having access to sufficient safe water. $30 billion spent per year to improve water supplies and sanitation yet there are 1.2 billion people without access to clean water with many of them living in the 20 or so developing countries classified as 'water scarce'. problems with water insecurity is related to:
- availability- having a water supply and distribution network.
- access- freedom to use or income to buy water in a particular location.
- usage- entitlement to, and understanding of, water use and health issues.
The water poverty index (WPI)
The index uses five parameters:
- resources- the quality of surface and groundwater per person, and its quality.
- access- the time and distance involved in obtaining sufficient safe water.
- capacity- how well the community manages its water and health.
- use- how economically water is used in the home and by agriculture and industry.
- environment- ecological sustainability (green water).
Poverty - lack of water hampers attempts to reduce poverty and encourage development. improved water supply can increase food production and bring better health and provide higher standards of wellbeing. water wealth in developed countries brings cheap water , irrigation, energy and economic growth.
The price of water - as demands increase, water prices set to follow oil and food upwards. Water free in developing but often needs to be carried over long distances and is likely to be contaminated. Price of freshwater depends on transport cost and level of demand
- California cites import water from the Colorado river basin - energy expensive.
- Australia's water price increased twenty-fold in December 2006 due to prolonged drought.
- water scarcity prompted farmers to sell their abstracted water instead of using ti for irrigation.