4.3 Water supply

Question 1

different sources of fresh water used by people
(5)

Answer 1

1. aquifers,
2. wells,
3. rivers,
4. reservoirs,
5. desalination plants

Question 2

sources of surface water, ground water and sea examples

Answer 2

• (Fresh water is often very visible on the earths surface) surface water: lakes,rivers and swamps.
• A lot more water is stored in Ground water: water present in the soil or in rocks under the surface of the ground
• Fresh Water is available from the sea if desalination is done

Question 3

aquifers

Answer 3

• water stored in porous rock underground, Groundwater can be extracted using a water well.
• If the water is stored under pressure ,the aquifer is called artesian aquifer.

Question 4

wells

Answer 4

A hole bored or dug into rock to reach the water stored there. Wells can be either near the surface or they can draw up water from very deep.

Question 5

ground water sources

Answer 5

aquifers and wells

Question 6

reservoir

Answer 6

an artificial lake where water can be stored

Question 7

Water from rivers:

Answer 7

• Can be obtained simply dipping buckets into it.
• By constructing reservoirs-Dams
• service reservoir-

Question 8

service reservoir

Answer 8

where Potable (drinking) water is stored in reservoirs

Question 9

desalination

Answer 9

removal of salt from seawater

Question 10

desalination by distillation

Answer 10

• Water is boiled and released as vapour,leaving the salt behind.The vapour is condensed as liquid water and can be used.
• 10-30% efficient
• uses a lot of energy (cause boiling= lots of heat energy)
• can be a source of pollution.

Question 11

desalination by reverse osmosis

Answer 11

• Salt water is pumped at high pressure through very fine semi permeable membranes.these block passage of salt and minerals.only fresh water flows through the membranes
• 30-50% efficient
• requires less energy than distillation (only uses force for pressure)

Question 12

Water from the sea:

Answer 12

Two processes can be used to make salt water potable:
* 1st method of desalination is by distillation
* 2nd method desalination by reverse osmosis

Question 13

reverse osmosis process

Answer 13

Water molecules move from low water potential (because of salt pressence in seawater) to high water potential (only water now no salt as it passes through the membrane) through a partially permeable membrane (so there will be a balance in the concentration of water between the two sides)