Learning Objectives
Chapter Overview
Key skills you will develop by the end of Chapter 2: Water Sources and Management.
Identify the major sources of water on Earth and in Pakistan
Explain the different types of precipitation — rain, snow, hail and sleet
Describe the water cycle and the four processes that drive it
Explain the reasons for the rising demand for water
Explore ways to increase and purify the water supply (reclamation, catchment, desalination)
Identify biogas as a renewable source of energy and describe water conservation
Geography: Water Sources and Management
Complete chapter notes with all key terms and vocabulary: PDF format
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Part 1
Water Supply
Where water is found on Earth, salty vs freshwater, and the key figures.
Sources of Water on Earth
1. What is water and in what two forms is it found on Earth?
• Name the two forms of water on Earth• In what two forms does water occur?
Water is one of the most important natural resources on Earth. It occurs in two forms — salty (sea) water and freshwater. No living thing can survive without it.
2. What are the three main sources of freshwater?
• Name the sources of fresh water• From where do we get freshwater?
The three main sources of freshwater are ice and snow in glaciers, rivers and lakes on the surface, and ground water under the surface of the Earth.
3. Why is the Earth called the Blue Planet?
• Why does Earth look blue from space?
About 70% of the Earth’s surface is covered with water. From space this water makes the Earth look blue, so it is called the Blue Planet.
4. How is Earth’s water divided between salt water and freshwater?
• What percentage of Earth’s water is salty?• How much of Earth’s water is fresh?
About 97% of Earth’s water is salt water in the seas and oceans, which cannot be used for drinking or farming. Only about 3% is freshwater.
5. How is the freshwater on Earth stored?
• Where is most freshwater found?• Give the split of freshwater stores
Of all freshwater, about 79% is frozen in ice caps and glaciers, about 20% is groundwater, and only about 1% is easily-available surface water in rivers, streams and lakes.
6. Why is sea water not fit for drinking or agriculture?
• Why can we not use sea water directly?
Sea water is salty and contains a high concentration of minerals (salt). This makes it unfit for drinking or growing crops, although it provides a habitat for sea life.
7. What is the difference between standing and floating water bodies?
• Give examples of standing and floating water bodies
In standing water bodies (lakes, ponds, inland wetlands) the water stays still. In floating water bodies (streams, rivers) the water flows continuously. Both collect rainwater, the main source of freshwater.
8. For how long can a human survive without drinking water?
• Why is water so important for life?
A human being can survive only about three days without drinking water — which shows how important water is for life.
Part 2
Precipitation and Its Types
How water falls from the sky, and why rainfall is uneven around the world.
Types of Precipitation
9. What is precipitation?
• Define precipitation• What is meant by precipitation?
Precipitation is the falling of water from the sky. It can be in the form of rain, snow, hail or sleet.
10. What are the four types of precipitation?
• Name the forms of precipitation
The four types are rain (liquid droplets 0.5 mm or larger), snow (flakes of ice), hail (big, irregular, purely solid ice) and sleet (small, semitransparent ice balls).
11. What is the difference between rain and drizzle?
• How small is a drizzle droplet?
Rain is made of water droplets 0.5 mm or larger. Droplets smaller than 0.5 mm are called drizzle.
12. How is sleet different from hail?
• Compare sleet and hail
Sleet is made of small, semitransparent balls of ice, while hailstones are bigger, irregular solid lumps. In short, sleet is smaller than hail, and hail is purely solid.
13. Why is precipitation unevenly distributed across the world?
• Why do some regions get more rain than others?
Because of constant heating and the global circulation of air. Tropical regions receive high rainfall, while desert regions receive very little.
14. Which regions face water scarcity, and where are they found?
• Where are many water-scarce countries located?
Regions that receive low precipitation face water scarcity. Many such countries lie in Africa and the Middle East, where droughts are common.
Part 3
The Water Cycle
The four processes that move water between the sky, land and sea.
The Hydrological Cycle
15. What is the water cycle (hydrological cycle)?
• Define the hydrological cycle• What keeps the Earth’s water moving?
The water cycle is the continuous movement of water from the atmosphere to the land and from the land back to the atmosphere. It keeps the Earth’s water supply going.
16. What are the four processes of the water cycle?
• Name the steps of the water cycle
The four processes are precipitation, evaporation, transpiration and condensation. Together they keep water moving between the sky, land and sea.
17. What is evaporation?
• How does water rise into the air?
Evaporation is the change of a liquid into water vapour. The Sun’s heat warms the water in rivers and seas, so water molecules rise into the atmosphere as vapour.
18. What is transpiration?
• What is the role of plants in the water cycle?
Transpiration is the process in which plants give off moisture into the atmosphere. Their roots absorb water from the ground and release it as vapour through the leaves.
19. What is condensation and how are clouds formed?
• How do clouds form?
Condensation is the change of water vapour into water. As vapour rises and cools, it condenses into tiny droplets that gather together to form clouds, which later fall as precipitation.
20. What is the difference between surface runoff and infiltration?
• Where does rainwater go after it falls?
Surface runoff is rain that flows over the ground into streams and rivers. Infiltration is rain that soaks through the surface and adds to the groundwater.
21. Why is the Sun important for the water cycle?
• What provides the energy for the water cycle?
The Sun’s heat causes evaporation, which lifts water into the atmosphere. Without this energy, the water cycle could not continue.
Part 4
Rising Demand for Water
Why the world needs more and more water every year.
Reasons for Rising Demand
22. What are the three main reasons for the rising demand for water?
• Why is the demand for water increasing?
The three main reasons are population growth, agriculture and industrialisation. Each of these needs very large amounts of water.
23. How much freshwater is used in households and in agriculture?
• Which sector uses the most freshwater?
About 7% of freshwater is used in households, while about 69% is used in agriculture — by far the biggest user.
24. How is water used in industry?
• How do factories and power plants use water?
Industries use water to cool engines and machinery, and in hydroelectric power plants a huge volume of water turns massive turbines to produce electricity.
25. How does population growth increase the demand for water?
• Why do more people mean more water is needed?
As the population grows, more people compete for the limited water supply and need extra water for basic needs like bathing, cooking, drinking and washing.
26. What problem is caused by over-using underground water?
• Why is the water table falling in some countries?
When too much underground water is drawn for farming, the water supply runs very low and the water table falls.
Part 5
Sewage, Catchment and Desalination
Ways to increase and purify the water supply.
Increasing the Water Supply
27. What is water reclamation and why is it useful?
• What does reclaiming water mean?
Reclamation means purifying used (sewage) water — removing solid materials, bacteria and impurities — so it can be used again. This reduces the pressure on the freshwater supply.
28. Can all reclaimed water be used for drinking?
• What is partly-purified reclaimed water used for?
No. Water that has gone through only the initial stages of purification cannot be drunk, but it can be used for industry and agriculture. Fully purified water can reach potable (drinkable) standards.
29. What is a water catchment area?
• Define catchment area
A catchment area is an area where all the water and sediments drain into a common outlet, such as a stream, reservoir or underground aquifer. Even cities are catchment areas.
30. Why is careful management of catchment areas important?
• How does land use affect a catchment?
Careful management keeps the water clean and healthy and lets more water be collected with less waste. Clearing trees, for example, washes more sediment into rivers.
31. What is desalination?
• Define desalination• How is salt removed from seawater?
Desalination is the removal of salt from seawater to obtain freshwater. It is done by distillation or membrane filtration.
32. How does distillation produce freshwater?
• Explain the distillation method
In distillation, the sea water is heated so it evaporates; the water vapour is then cooled and condensed into freshwater, while the salt is left behind.
33. How does the membrane method work?
• What does a semipermeable membrane do?
Water is forced through a semipermeable membrane that lets water molecules pass but blocks the salt, so freshwater comes out the other side.
34. What is one disadvantage of desalination?
• Why is desalination not used everywhere?
Desalination is expensive because it needs costly equipment and a lot of energy (especially the distillation method), which many countries cannot afford.
Part 6
Biogas and Water Conservation
A renewable energy source, and how we save water.
Biogas and Conservation
35. What is biogas and how is it produced?
• How is biogas made?• From what is biogas produced?
Biogas is a gas made when organic waste (food scraps and animal waste) is decomposed by bacteria in an airtight biodigester through anaerobic respiration (respiration without oxygen).
36. What are the uses of biogas?
• How can biogas be used?
In compressed form it can be used as vehicle fuel; when refined to the standard of natural gas, it can be used for cooking and heating. A biogas plant also gives biofertiliser.
37. Why is biogas an environmentally friendly, renewable energy source?
• Why is biogas called renewable?
Its raw material — organic and animal waste — is produced all the time, so it never runs out. It turns waste into clean energy without harming the environment.
38. Which country leads in biogas and why is it useful for Pakistan?
• How can biogas help Pakistan?
China has the largest number of biogas plants, mostly in rural areas. In Pakistan, biogas can give cheap, clean energy in villages from farm and animal waste, saving natural gas.
39. What is water conservation and why is it needed?
• Define water conservation
Water conservation means reducing the use and wastage of water. It is needed because freshwater is limited and must be saved for future generations.
40. How do education and technology help conserve water?
• Give ways to conserve water
Education teaches people the value of water. Technology provides water-saving gadgets for taps and toilets and improved irrigation that reduces the water lost during farming.
41. Give three simple ways to save water at home.
• How can a student save water?
Take shorter showers, turn off the tap while brushing teeth or soaping hands, and wash only full loads. Low-flow showerheads and faucet aerators also help.
Key Terms
Vocabulary & Definitions
Important words from this chapter and what they mean.
| Term | Definition |
|---|---|
| Blue Planet | The name for Earth because about 70% of its surface is covered with water |
| Salt water | Water with a high concentration of minerals that is not drinkable but is a habitat for sea life |
| Freshwater | Water without a significant amount of salt that is drinkable and used for domestic, agricultural and industrial purposes |
| Standing water body | A water body where the water stays still, such as a lake, pond or inland wetland |
| Floating water body | A water body where the water keeps flowing, such as a stream or river |
| Groundwater | The layer of water found under the layers of rocks below the surface of the Earth |
| Precipitation | The falling of water from the sky in the form of rain, snow, hail or sleet |
| Rain | Liquid water droplets of 0.5 mm or larger that fall from the clouds |
| Drizzle | Precipitation made of very small water droplets, less than 0.5 mm in size |
| Snow | Precipitation in the form of flakes of ice that fall from the clouds |
| Hail | Big, irregular, purely solid lumps of ice that fall from the sky |
| Sleet | Precipitation made of small, semitransparent balls of ice, smaller than hailstones |
| Drought | A long period of very little or no rainfall that causes a shortage of water |
| Water cycle | The continuous movement of water from the atmosphere to the land and back to the atmosphere |
| Evaporation | The change of a liquid into water vapour |
| Transpiration | The process in which plants give off moisture into the atmosphere |
| Condensation | The change of water vapour into water, forming clouds |
| Surface runoff | Precipitation that flows downhill over the ground until it reaches a stream or water body |
| Infiltration | The precipitation that does not run off but percolates through the surface into the ground |
| Water reclamation | Purifying used (sewage) water so that it can be used again |
| Potable water | Water that is clean and safe for drinking |
| Cloud seeding | Dispersing chemicals into the air so that water droplets form more easily to increase rainfall |
| Catchment area | An area where all the water and sediments drain into a common outlet such as a stream or reservoir |
| Desalination | The removal of salt from seawater to obtain freshwater |
| Distillation | A desalination method in which sea water is heated and the vapour is cooled to form freshwater |
| Semipermeable membrane | A barrier that lets water molecules pass through but blocks salt molecules |
| Biogas | A gas produced when organic waste is broken down by bacteria |
| Anaerobic respiration | A kind of respiration that does not need oxygen |
| Biodigester | The airtight chamber in which organic waste is decomposed by bacteria to make biogas |
| Water conservation | Reducing the use and wastage of water to save water resources |
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