Lecture 8 Topic: Water resources problems

Section objectives:

1. Importance of water for life.

2. Ecological consequences of water deficiency and water pollution

3. Sources of water pollution

4. Sustainable strategies on water resources problem. International cooperation

1. Importance of Water for Life

Fresh water is essential to life on Earth. 70% of the Earth's surface is covered in water, but only 3% of this water is fresh water (as opposed to marine, or salty water), and most of this is locked up in ice caps and glaciers. Less than 1% of fresh water is available for life.

Water is 100% recyclable. However, water that is fit to use is limited resource, because it may not always be accessible and can be polluted.

The availability of water in any areas depends on how much there is, where it is, how much is used and what its quality is. These factors all affect the location, health and development of the population and the industries connected with it.

73% of the water used in the world is used for agriculture, 21% - by industry, and 6% - for domestic use. These proportions vary from country to country. For instance, there is more demand in western countries for domestic and industrial uses of water. By contrast, in less developed countries water is used much more for agricultural irrigation.

There are many sources of water supply: rivers, streams, reservoirs, and groundwater.

Biological needs are 2-5 L/day, but real consumption of water to a person is 1500-2000 L/day. The main reason why this demand is so high is that water is often cheap. Its cost is not decided by its environmental value or its potential scarcity. This means that it is usually used wastefully.

Water is as important to industries as it is to life at home: as a food ingredient, a coolant, and a solvent, for washing and for the dilution of pollution. Different products need different amounts.

• Industries usually receive water from the same supply as homes. However, when industries require large amounts of water, they can take it directly from rivers - although they need a special license for doing so.

• The water footprint of China is about 700 cubic meter per year per capita. Only about 7% of the Chinese water footprint falls outside China.

• Japan with a footprint of 1150 cubic meter per year per capita, has about 65% of its total water footprint outside the borders of the country.

• The USA water footprint is 2500 cubic meter per year per capita.

Water renewal rate in aquatic ecosystems:

• Rivers – 12-17 days

• Lakes – 17 years

• Underground water – 1400 years

2. Ecological consequences of water deficiency and water pollution

In dry countries, water shortage is a fact of life, and water is a precious resource.

Countries with wetter climates often take water for granted and use it wastefully.

Large populations and their related development pressures, such as a new housing, public facilities and industry, cause high demand. These are all further drains on the existing water supply.

The amount used in the home for different purposes can be surprisingly high. Using a house-pipe for one hour uses as much water as a family of four uses in a week!

Reserves of groundwater are becoming reduced and polluted (nitrates, fertilizers, pesticides).

"Eutrophication" - state when water becomes so over-enriched with nutrients that organisms such as algae and phytoplankton multiply, at the expense of other water plants. This produces "algal blooms", which starve water of oxygen and shade out the sunlight. The result is that other forms of aquatic life can no longer survive. Effluents can also cause Eutophication from sewage and industrial waste that also contain nitrates and phosphates.

Eutrophic lakes are rich in organic matter and vegetation, making the waters relatively murky.

Oligotrophic lakes contain little organic matter.

Irrigation and domestic uses of water waste more water than most industrial uses. However, industrial can cause serious contamination if they release polluted wastewater, known as effluent, from their processes into rivers and seas.

Many manufacturing processes can cause water pollution. It is not possible to re-use polluted water for most purposes, without expensive treatment; it is also damaging to wildlife and habitats.

Warm water is another form of pollution - thermal pollution Some wildlife is sensitive to temperature changes and can be upset if water returned to a watercourse immediately after it has been used for cooling.

Some rivers do not reach the sea now because there is so much demand for its water - rivers have vanished entirely. Disappearing rivers threaten water supplies and devastate wildlife and landscape.

Almost 80% of diseases in so called "developing" countries are associated with water, causing some three million early deaths. For example, 5,000 children die every day from diarrhoea, or one every 17 seconds.

In Kazakhstan about 50 percent of the population uses drinking water which doesn't meet [international] standards of salinity and hardness."