The blue planet
The hysdrosphere consists of all the wayer on the planet - in seas, oceans, rivers and lakes, in rocks and soil, in living things and in the atmosphere. Water exists on the Earths surface and in the atmosphere in three states: as a liquid (water); as a solid (ice); and as a gas (water vapour).
Water a continuous cycle - Water flows in a never ending cycle between the atmosphere, land and oceans. The hydrological cycle or water cycle, is a closed system. The water goes round and round , but none is added or lost from the system as a whole, so the Earth gets neither wetter now drier.
Revise more in the book: related stores, flows/transfers, inputs and outputs.
Learn the case studies.
The global hydrological cycle
The stores of the water are linked by processes which transfer water into them. These processes regulate the water cycle.
Evaporation from the oceans and rivers, and evapotranspiration from trees, condenses to cause precipitation (rainfall).
This precipitation follow a number of routes: some runs off over the surface, some seeps into the rock soil or rock and some collects as snow or ice.
The biosphere and lithosphere - The biosphere and lithosphere play a vital role in the water cycle, and act as sub - cycles. In the biosphere, trees intercept precipitation, and over half of it is then evaporated and transpired without ever reaching the ground. (This water is known as GREEN water). If the storm or rainfall is very heavy, or goes on for a long time, precipitation drips from the leaves and stems and slowly makes its way into the river system. Precipitation infiltrates the soil, where it flos down slope as throughflow, or if the underlying rock is permeable, into the ground, to be stored as groundwater - a vital supply of water. Only after many hours is the water released into the river basin. Both the biosphere and the lithosphere help to regulate the water cycle.
Infiltration - movement of water into the soil from the surface
Percolation - movement of water into underlying rocks
Groundwater storage - water stored in rocks following percolation
Saturation - when soil is full of moisture
Water table - the level at which saturation occurs in the ground or soil
Inputs - things which enter the system
Outputs - things which leave the system
Transfers or flows - movements within the system
Stores - held within the system
Water supplies in trouble
The world is currently facing a freshwater crisis. Demand is soaring as population increases, and supplies are becoming increasingly unpredictable. Many economists and experts predict that in the future we will have water wars, where countries fight over water resources - especially in the middle east.
Our use of water is increasing and much of the increasing demand is agriculture. Modern farming often requires irrigation, which uses vast quantities of water.
The increasing use of water for agriculture is having major impact on the amount of water remaining for other uses. A rapidly rising global population and constant economic development, espiacially in countries such as China and India, means that industrial and domestic demand has also grown. More water is needed for manufacturing industries, and rising living standards mean people use more water at home for showers, washing machines and so on.
Water stress and scarcity
So far, freshwater isn't actually scarce.
Globally, only half of the annual freshwater runoff (known as blue water) available for human use is currently used in agriculture, industry or for domestic use.
But much fresh water is either inaccessible (i.e.it falls in the place), or is available only at certain times of the year.
However, many parts of the world are now experiencing water stress. Many lakes, rivers and groundwater supplies are drying up from overuse. Water stress takes the form of shortages of water supplies, especially for irrigation. Turkmenistan and Uzbekistan in central asia are currently the mst water stressed countries in the world, as they use huge quantities of water irrigating crops such as cotton.
Currently most of North and South America and Northern Eurasia have plenty of water, but other areas suffer from water scarcity. Areas, such as the south - west USA and central asia, are experiencing physical water scarcity, where demand exceeds local availability.
Other areas, such as sub - saharan africa, experience economic water scarcity. Here, there are sufficient supplies available, but people cannot afford to exploit them. They lack the money to build water storage facilities to provide water for dry seasons, or to distribute water to rapidly growing cities.
page 61 - important words
The Sahel region suffers from water stress and also live in a state of chronic water shortage.
The Sahel is a narrow belt of semi - arid land immediately south of the sahara desert. Rain falls in only 1 or 2 months of the year, and both the total amount of rainfall (usually between 250 and 450mm) and the length of the rainy season are very reliable.Since 1970 rainfall has more often than not been below average - and in some cases up to 25% below average. Sometimes the rain comes in torrential downpours and is then lost as surface runoff, causing flooding. Recent years have seen several lengthy droughts: drought causes rivers and water holes to dry up and the water table to fall, animals die, grasses die, soil erosion and desertification follow, due to overgrazing by animals.
Many of the countries in the Sahel are developing countries such as Chad, Niger, Sudan and Ethiopa are among the poorest in the world.
The world bank estimates that by 2025, 50% of the water world's population will face water shortages.
Global warming will lead to: changes in the climate patterns, so rain - bearing winds will reach some areas less regularly, an increase in the rate of glacier melting, more extreme weather events and with floods and storms as well as droughts.
Richer countries can buy their way out of water stress - for example, Kuwait and Saudi Arabia can afford to build desalination plants (to convert sea water to drinking water) with the profits from their oil industries. However, rapid changes in weather patterns could spell disaster for poor subsistence farmers in developing countries, who rely on rain to water their crops. These farmers are increasingly vulnerable to unstable weather patterns and, for them, water insecurity will almost certainly lead to food insecurity and famine.
Threats to water quality
READ PAGE 64!!!
STUPID COMPUTER DECIDED TO RESTART IT SELF!!
Pollution in developed countries
Develooped countries like Japan and the Uk have taken big steps to control pollution. Their economies are heavily based on tertiary and quaternary activities, which cause less water pollution than primary and secondary industries.
In the late 1960's Japan's lakes, rivers and seas were polluted. The pollution caused major health problems and damaged ecosystems, for example mercury poisoning at Minamata. During the 1970's the Japanese government produced standards to improve water quality, and tackle pollution. Lake Biwa and the inland sea were polluted which now have high water quality, with swimming areas and fish farms. The rivers entering Tokyo and Osaka bay - 2 industrial areas are now almost free of pollutants.
Read the table and more on page 65
Interfering in the hydrological cycle
Human interference - Water creates wetland habitats which are important environmentally for their biodiversity. Many wetlands are protected as Ramsar sites.
The wide range of uses reflects the proccesses and links within the water cycle. Some of these have positive impacts and others have negative impacts on water supplies, and the downside of the links within the cycle means that overuse for one purpose, or disruption of the cycle, can have serious knock on effects elsewhere in the system.
Overabstraction - overabstraction of the water in the Thames Valley in southern england in recent years has led dramatic drop in river flow, with some tributary streams drying up completely damaging the river ecosystem, home to many plants and animals.
Most water companies now have a strict policies calles CAMS (catchment abstraction management strategies) for managing local water resources. Water levels are managed to keep the competing demands in the area in balance sufficiently high for all the users, but not so high that there is an increased flood risk.
Read more on page 67
Solutions to the water crisis
Sustainability - Water demand is rising and supplies can be unpredictable. If we use water faster than it can be replenished its use is not sustainable. Not only that but we need to store and distribute it efficiently - and this can be expensive.
There is still a huge amount to be done to provide access to reliable and safe water supplies for billions of people around the world. Strategies designed to use water more sustainably range from large scale schemes.
Read more at the blue box at page 68.
Dams may bring benefits in terms of increased water supply but they can have negative impacts too. Their construction plays a havoc with fragile aquatic ecosystems, destroying fisheries and wildlife. Both natural and cultural resources are submerged. Environmental groups and human rights activists campaign to halt and restrict dam construction.
Around 45,000 large dams worldwide affect 6 out of 10 major rivers and have caused about 80 million people to be forcibly relocated.
Read about the three gorges dam.
China's big schemes - centralised government enables it to develop huge schemes. Water is plentiful in the south of China, but scarce on the parched Northern plains, and likely to ger scarcer. China's answer to its water problems has been to develop major schemes such as the South to North water diversion project and the three gorges dam project.
Small scale solutions
Non government organisations such as WaterAid or Practical Action, often develop small scale sustainable solutions to local problems in developing couuntries. Local communities are involved in projects to develop safe and reliable water supplies. NGO's set up a low cost projects using appropriate or intermediate technology. This means that it is appropriate to the geogrpahical conditions of the local area, and within the technical ability of the local community so they can monitor and operate it themselves.
The schemes include rainwater harvesting, protecting springs from contamination, developing gravity fed piped schemes and building hand dug or tube wells for villages. Water can be obtained from hand dug or tube wells using buckets or treddle pumps.
Many of the NGO projects are in the rural areas but others have been developed to supply frsh water for the shanty towns in urban areas.
Read more on page 71.