Lesson what are the properties of water? Choose the correct answer

What is Groundwater?

1. When rain falls, some of it flows across the surface of the land and accumulates in rivers, lakes, and eventually the ocean.

2. But some of the water seeps into the ground and accumulates within cracks or pores in the rocks (aquifers), forming groundwater resources, which in turn also eventually flow into rivers, lakes or the ocean.

3. Approximately 2 per cent of the Earth's water occurs as groundwater, compared with 0.1 per cent as rivers and lakes and 94 per cent as oceans.

4. In Australia, groundwater makes up approximately 17 per cent of accessible water resources and accounts for over 30 per cent of our total water consumption.

5. Some groundwater is fresh and can be used for drinking.

6. Other groundwater can be brackish water or even saltier than the sea.

7. Some contain high levels of dissolved chemicals, rendering it unsuitable for human consumption or stock water supplies.

How is it extracted?

8. Depending on the permeability of the rocks containing the groundwater, and the pressure under which groundwater is held; the ease of groundwater extraction can

vary significantly.

9. Both water quality and aquifer yield determine whether groundwater is appropriate for human consumption, stock water supplies, irrigation, or mining uses.

10. The salinity and yield characteristics of groundwater resources vary considerably across the continent.

11. Groundwater is particularly important as a water resource in semi-arid to arid parts of Australia, where rainfall is too infrequent or inadequate to reliably meet water needs.

12. Often such groundwater resources have accumulated over long periods and are replenished only when rainfall is sufficient to infiltrate soil and rock.

13. This means groundwater can be a finite or slowly replenished resource.

14. In more temperate areas where rainfall rates are higher, groundwater may be replenished on a regular basis and extraction can be managed on a renewable basis.

15. However, in many instances groundwater use in Australia exceeds the rate at which

groundwater is replenished.

16. The Australian Water Resources 2005 concluded that 30 per cent of Australia's groundwater management units were at a high level of development and approaching or beyond sustainable extraction limits.

LESSON 14.

1. The Aral Sea, once the fourth largest lake in the world, has shrunk by more than half of its surface and by more than two thirds of its volume.

2. Since 1960 its water level has fallen by more than 16 meters and its salinity has increased by more than 15 three times.

3. The former sea bed is now a barren salt desert.

4. The shrinkage of the sea is easily explained.

5. The Aral Sea has no outflow so, in the past, nature kept a balance by replacing the water which evaporates in the hot sun (about 60 cubic kilometers each year) with new water brought by its two feeder rivers the Amu Darya and the Syr- Darya.

6. However, the rise in demand for water to irrigate the cotton crops of Central Asia and to supply the growing population has led to more and more water being taken from the Amu Darya, the Syr Darya and their tributaries.

7. As a result, the natural balance has been broken and the amount of water reaching the Aral Sea is no longer enough to replace that lost through evaporation.

8. Consequently, the volume and level of the sea are decreasing, its shoreline is retreating, and its salinity is increasing.

9. The drying up of the Aral Sea is one of the world's major environmental disasters.

10. Not only is the environment around the lake being destroyed, but the livelihood and health of the people who live there are also being damaged.

11. The cotton harvest in the fields of the Amu Darya delta is declining since the reduction in the area of the Sea has changed the local climate and resulted in a shorter growing season.

12. The fertility of the soil has also been reduced by the salt blown off the dry seabed.

13. Because of this drop in fertility, farmers use more chemicals on their land.

14. These chemical fertilizers and pesticides have polluted the rivers and the Aral Sea itself.

15. Drinking water taken from these sources is also polluted.

16. In addition, the air contains salt, dust and pollutants blown from the sea bed.

17. This pollution of the air and water is causing serious health problems.

18. Many people suffer from anemia, breathing difficulties and stomach problems including gastritis.

19. The infant mortality rates increased by 20% from 1980 to 1989 and have long been the highest in the Republic.

20. Doctors say that these health problems are due to the bad water and polluted air.

21. Several international organizations including the UNDP and UNEP are now helping the Government of Uzbekistan to tackle the problem of the Aral Sea.

22. The World Bank is giving over $30 million to help save the Sea and expensive research projects and international conferences of experts are planned. In fact, there is a joke that if every expert who visits the Aral Sea brought a bucket of water the problem could be solved!

23. But for the people of the area it is no laughing matter.

24. Written in chalk on the side of a ship stuck in the sand near Muynak are the words, "Forgive us Aral. Please come back!"

25. Whether the Aral is prepared to forgive us is still an unanswered question.
LESSON 15.