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Citing sources: Exercises

Exercise 13

Read the articles below and, in a paragraph of not more than 250 words, discuss the problems for the human race with regard to water. Cite any sources you use.

Water H2O.

The commonest molecular compound on Earth; a liquid, freezing to ice at 0°C and boiling to steam at 100°C. It covers about 75% of the Earth's surface, and dissolves almost everything to some extent. It is essential to life, and occurs in all living organisms. It is strongly hydrogen-bonded in the liquid phase, and co-ordinates to dissolved ions. Unusually, the solid is less dense than the liquid; this results in ice floating on ponds, and accounts for the destructiveness of continued freezing and thawing. Water containing substantial concentrations of calcium and magnesium ions is called 'hard', and is 'softened' by replacing these ions with sodium or potassium, which do not form insoluble products with soaps.

From: The Cambridge Encyclopaedia by David Crystal. It was published in Cambridge by Cambridge University Press in 1990 and the extract is from page 1285.)


Crisis and challenge

Today in almost every area of the world one chooses to look at there is a water problem - scarcity, depletion, pollution, lack of sanitation, failing rains due to global warming, big dam projects blocking up rivers, privatisation, inequities of distribution, cross-border conflict, profligate use and mismanagement. Take your pick. But let's start with overuse.

We learn at school that freshwater on earth follows a cycle: it is constantly being replenished, some of it soaking into the ground and into vegetation, some of it meandering through streams and rivers on its way back to the sea. But at what stage of our lives do we forget this important lesson? The moment one starts using freshwater beyond the rate at which it can be replenished, the hydrological cycle is endangered.

The crisis is particularly acute in relation to our groundwater reserves, lying deep under the surface in aquifers, upon which a third of the world's population depends. Water can take thousands of years to percolate into aquifers (some contain water from the last ice age). Some have since sealed up, allowing little possibility of recharge. Because the reserves of water they hold are large, humans have been tapping them like there is no tomorrow. Currently we are pumping out about 200 billion cubic metres (1 cubic metre = 908 litres) more than can be recharged, steadily using up our water capital.

Take California with its manicured lawns and 560,000 swimming pools. Having taxed the Colorado River to the limit, the region's aquifers are being guzzled up. By 2020 officials predict a water shortfall nearly equivalent to what the state is currently using. Another more distant water source needs to be found to gulp down. Consumption is the operative word for US water use.

(From an article by Dinar Godrej called "Precious fluid". It was published the New Internationalist magazine, volume 354. It was published in, March 2003 on pages 9-12. This extract is from page 10.)


The Ocean

Approximately three fourths of This Earth of Ours is covered by the ocean, which modifies its climate, receives its sediments, and determines the configuration of its shores. It has been estimated that the average depth of the ocean is about 2½ miles and the average height of the continents about ½ mile, so that if all of the land were cut off at sea level and placed in the ocean basins, it would fill only one fortieth of the depression. The term average depth does not give a true picture of the ocean floor, which contains islands that rise 3 or 4 miles above a general level and depressions or deeps that descend about an equal distance. Off the coast of the Philippine Islands is the greatest known depression 35,433 feet deep and the Tuscarora Deep near Japan exceeds 28,000 feet. In the Atlantic soundings over 27,000 feet have been recorded near Puerto Rico. The great deeps of the ocean are of approximately the same magnitude as the highest elevations on land, for Mt. Everest, the highest measured mountain, exceeds 29,000 feet.

(By Doctor Victor T. Allen, MS, PhD. This is from an old book called This earth of ours. It was published in 1939 in Milwaukee by The Bruce Publishing Company. This section is from page 160.)


  • On our blue planet 97.5% of the water is saltwater, unfit for human use.
  • The majority of freshwater is beyond our reach, locked into polar snow and ice.
  • Less than 1% of freshwater is usable, amounting to only 0.01%of the Earth's total water.
  • Even this would be enough to support the world's population three times over if used with care.
  • However, water - like population - isn't distributed evenly. Asia has the greatest annual availability of fresh-water and Australia the lowest. But when population is taken into account the picture looks very different.
  • Our increasing thirst is a result of growing population, industrial development and the expansion of irrigated farming. In the past 40 years, the area of irrigated land has doubled.'
  • By the mid-1990s, 80 countries home to 40% of world population encountered serious 'water shortages. Worst affected are Africa and the Middle East.
  • By 2025 two-thirds of the world's people will be facing water stress. The global demand for water will have grown by - over 40% by then.
  • The only ray of hope is that the growth in actual use of water has been slower than predicted.
  • Dirty water is the cause of numerous diseases, but improving hygiene and sanitation are equally important in order to curb water-related diseases.

(From an article in New Internationalist called Water: The facts. It was on page 18 of the March 2003 issue. This was volume 354.)


Water Pollution

Water pollution affects oceans, streams, rivers, lakes, ponds, and groundwater, and can be caused by natural impurities or human activities that pollute the nearby water or water supplies.

Natural impurities in water are sometimes, but not always, pollutants. They are divided into three categories of particles: suspended particles that absorb light and make water cloudy, such as beach sand, coal dust, and bacteria; colloidal particles, such as soot and some viruses, which cannot be removed from water by ordinary filtration and cause the water to look cloudy when observed at right angles to a beam of light; and dissolved matter, which are the 'smallest impurities in water, including molecules and ions of various substances, such as chloride or sodium ions or carbon dioxide molecules.

Human activities are often the cause of localized water pollution, as water becomes contaminated with heavy metals, toxic chemicals, and bacteria. Rivers may experience oil and chemical spills, untreated sewage runoff from homes and industry, and nonpoint source pollution, such as contaminated runoff from highways, parking lots, and agricultural fields. Groundwater (or subsurface water) may be contaminated by the infiltration of pollutants from landfills and septic tanks, or by percolation of water containing contaminated runoff. Parts of the ocean are sometimes polluted by oil tanker spills and garbage dumping.

(This was written by Patricia Barnes-Svarney, in "The New York public library science desk reference". It was published in New York by Macmillan in 1996 and this paragraph is from page 472.)


Some 1.2 billion people lack access to clean water, twice that number have no sanitation, and most of the world will not have enough water within 30 years. This combination of scarcity and bad management affects food supplies, health, education, nature and economic development. It means women spend long periods collecting it, families spend up to half their daily income on it, farmers lose their land, and infants die.

Global consumption of freshwater is doubling every 20 years and new sources are becoming scarcer and more expensive to develop and treat.

In 1996, says the UN, humanity used about 54% of all the accessible freshwater contained in rivers, lakes and underground aquifers. This is conservatively projected to climb to at least 70% by 2025, reflecting population growth alone, and by much more if per capita consumption rises at its current pace.

Some 70% of all the world's fresh water used by man goes to grow food, and in parts of the US, North Africa and Asia, farmers can take up to 95%. Unavoidable population increases in the next 20 years will mean that agriculture alone will need at least 17% more water than it does now just to grow the extra food these people will need.

(Blue gold: Earth's liquid asset John Vidal, The Guardian, August 2002, p. 6.)

 

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