Water Resources — Study Notes

Not in Sec 2 2026: Water Resources is a Sec 1 topic under the “Sustainable Management of Natural Resources” theme. It is not examinable in the Sec 2 2026 Geography paper. The Sec 2 examinable theme is “Sustainable Urban Development” (Urban Housing, Urban Transport, Geographical Investigation, and Sustainable Cities). Note that Singapore’s Four National Taps (including NEWater) is also referenced in the Sec 2 Sustainable Cities topic — study that content through the urban-development notes. These notes are kept for background reference.

Key Concepts

1. Water as a natural resource

Water is a natural resource that all living things need to survive.
Humans need water for:
- drinking
- cooking
- washing
- farming
- industry
- generating electricity
Although Earth has a lot of water, not all of it is usable by humans.

2. Global distribution of freshwater

Water on Earth is unevenly distributed between salt water and fresh water.
About 97% of Earth’s water is salt water, mainly in oceans and seas.
Only about 3% is fresh water.
However, most freshwater is not easily available for human use:
- about 69% of freshwater is trapped in ice caps and glaciers
- about 30% is found as groundwater
- less than 1% is found in rivers, lakes and the atmosphere
This means only a very small amount of Earth’s water is easily accessible for daily human use.

Why accessible freshwater is limited

Some freshwater is frozen.
Some is deep underground and difficult to extract.
Some water is polluted and unsafe.
Some places receive much less rainfall than others.

3. Freshwater sources

Main sources of freshwater include:
- rivers
- lakes
- reservoirs
- groundwater
- rainwater
In some countries, people also obtain freshwater from:
- desalination of seawater
- recycled wastewater

4. Water scarcity and water stress

Water scarcity happens when there is not enough safe and accessible water to meet people’s needs.
Water stress happens when the demand for water is close to or greater than the available amount during a certain period.
A place may experience water scarcity because:
- there is very little rainfall
- water sources are polluted
- the population is too large
- water is poorly managed
Water stress can happen even in places that receive rain if:
- many people use a lot of water
- industries and farms need large amounts of water
- there is a long dry season

5. Causes of water scarcity

Water scarcity is caused by both physical factors and human factors.

5a. Physical factors

These are natural causes.

Low rainfall
- Some regions are naturally dry, such as deserts.
- If annual rainfall is low, rivers and reservoirs do not receive enough water.
Uneven distribution of rainfall
- Some places have heavy rain during only part of the year.
- Long dry seasons can lead to shortages.
Drought
- A drought is a long period with much less rainfall than usual.
- Drought reduces water levels in rivers, lakes and reservoirs.
Climate
- Hot climates increase the rate of evaporation.
- More water is lost from water bodies and soil.
Limited natural freshwater sources
- Some countries have few rivers, lakes or groundwater sources.

5b. Human factors

These are causes linked to human activities.

Population growth
- More people need more water for drinking, washing and sanitation.
- Greater population increases pressure on water supplies.
Urbanisation
- Urbanisation is the growth of towns and cities.
- Cities need large amounts of water for homes, industry and services.
Industrial use
- Factories use water for cooling, cleaning and manufacturing.
- This increases demand for water.
Agriculture
- Farming uses large amounts of water for irrigation.
- In many parts of the world, agriculture is the biggest user of freshwater.
Pollution
- Water may become unsafe because of:
  - sewage
  - industrial waste
  - oil spills
  - fertilisers
  - pesticides
- Polluted water cannot be used unless it is treated.
Poor water management
- Water may be wasted because of leaking pipes, inefficient irrigation or poor planning.
- Lack of reservoirs or treatment plants can worsen shortages.
Over-extraction of groundwater
- If groundwater is removed faster than it is replaced by rain, wells may dry up.
- Ground may also sink in some places.
Climate change
- Human activities increase greenhouse gases, causing climate change.
- Climate change can alter rainfall patterns and increase drought frequency in some regions.

6. Impact of water scarcity on people

Water scarcity affects health, daily life and development.

Lack of clean drinking water
- People may be forced to drink unsafe water.
- This can spread water-borne diseases.
Poor sanitation
- Without enough water, toilets cannot be used properly.
- Hygiene becomes difficult, increasing the spread of disease.
Health problems
- Dehydration, illness and poor hygiene may occur.
- Children and elderly people are especially vulnerable.
Reduced food production
- Crops need water to grow.
- Water shortages can reduce harvests and cause food shortages.
Loss of income
- Farmers may lose crops and livestock.
- Industries may slow down or stop if water supply is limited.
Time spent collecting water
- In some places, people must walk long distances to fetch water.
- This reduces time for school or work.
Conflicts
- Competition over limited water resources may lead to arguments between communities, regions or countries.

7. Impact of water scarcity on the environment

Drying up of rivers and lakes
- Habitats shrink or disappear.
Death of plants and animals
- Organisms may die if water sources disappear.
Loss of biodiversity
- Biodiversity is the variety of living organisms in an area.
- Fewer species can survive in dry conditions.
Soil degradation
- Dry soil may become less fertile.
Desertification
- Desertification is the process where fertile land becomes desert-like due to drought, deforestation or poor farming practices.
Concentration of pollutants
- When there is less water, pollutants become more concentrated and more harmful to aquatic life.

8. Sustainable water management

Sustainable management means using water wisely so that current needs are met without reducing the ability of future generations to meet their needs.
The aim is to ensure enough clean water for a long time.

9. Sustainable water management strategies

Different countries use different strategies depending on climate, land area and technology.

a) Protecting water catchment areas

A water catchment area is land where rainwater is collected and drains into rivers, lakes or reservoirs.
Protecting catchment areas helps keep water clean.
Ways to protect them:
- prevent dumping of waste
- control pollution
- preserve vegetation
- monitor land use

b) Building reservoirs and dams

Reservoirs store water during rainy periods for use during dry periods.
Dams can control water flow and reduce shortages.
However, dams may also affect habitats and displace people.

c) Water treatment

Dirty water can be treated to remove harmful substances.
Water treatment makes water safe for drinking or other uses.

d) Recycling water

Used water can be cleaned and reused.
This reduces the need to depend only on rainfall or rivers.

e) Desalination

Desalination removes dissolved salts from seawater to produce freshwater.
It is useful for countries with little natural freshwater.
However:
- it requires a lot of energy
- it is expensive
- it can have environmental impacts if waste brine is not managed properly

f) Efficient irrigation

Farmers can use methods such as drip irrigation.
Drip irrigation delivers water slowly to plant roots.
This reduces water loss by evaporation and runoff.

g) Reducing water pollution

Proper treatment of sewage and industrial waste keeps freshwater sources clean.
Less pollution means more water remains usable.

h) Water conservation

Water conservation means reducing unnecessary water use.
It can be done by:
- turning off taps when not in use
- fixing leaks
- using water-efficient appliances
- reusing water when possible
- educating the public

i) Public education and laws

Governments can:
- educate people about saving water
- introduce laws against pollution
- price water carefully to discourage wastage

10. Singapore’s water management

Singapore has limited land area and no large natural lakes. It must manage water very carefully.

Why Singapore needs strong water management

Singapore has:
- a small land area
- limited natural freshwater sources
- a high population density
- significant water demand from homes and industries
As a result, Singapore has developed a long-term strategy for water security.

11. Singapore’s Four National Taps

Singapore’s water supply comes from four main sources, known as the Four National Taps:

a) Local catchment water

Rainwater is collected in reservoirs and catchment areas.
About two-thirds of Singapore’s land area is used as water catchment.
Examples include:
- reservoirs
- canals
- rivers connected to collection systems

b) Imported water

Singapore has imported water from Malaysia under water agreements.
Imported water has been an important source, especially in the past.

c) NEWater

NEWater is high-grade reclaimed water produced from treated used water.
It is cleaned using advanced treatment processes:
1. Microfiltration / ultrafiltration removes suspended particles and some microorganisms.
2. Reverse osmosis removes dissolved salts, viruses and very small impurities.
3. Ultraviolet disinfection kills remaining microorganisms.
NEWater is used mainly for:
- industry
- air-conditioning cooling systems
- topping up reservoirs
NEWater is safe and of very high quality.

d) Desalinated water

Seawater is treated to remove salts and impurities.
This provides a source of water that does not depend on rainfall.
Desalination helps improve Singapore’s water security.

12. Water conservation in Singapore

Singapore encourages everyone to save water.

Methods used in Singapore

Public education campaigns
- encourage responsible water use
Water-efficient devices
- such as low-flow taps and dual-flush toilets
Fixing leaks quickly
- prevents unnecessary loss of water
Water pricing
- reminds people that water is valuable
School and community programmes
- teach good habits from young

Simple ways individuals can save water

turn off taps while brushing teeth
take shorter showers
wash full loads in washing machines
use a pail instead of a running hose when washing
repair leaking taps

13. Why sustainable water management matters

Water is essential for:
- life
- health
- food production
- industry
- ecosystems
Poor management can lead to shortages, pollution and environmental damage.
Sustainable management ensures a reliable supply of clean water now and in the future.

Important Definitions

Water resource: a source of water that people can use.
Fresh water: water that contains very little dissolved salt and is suitable for many human uses after treatment.
Salt water: water with a high amount of dissolved salts, mainly found in oceans and seas.
Groundwater: water stored underground in spaces between soil particles and rocks.
Reservoir: a natural or artificial lake used to store water.
Water catchment area: an area of land where rainwater is collected and drained into a reservoir, river or lake.
Water scarcity: a situation where there is not enough safe and accessible water to meet needs.
Water stress: a condition in which demand for water is close to or greater than the available supply.
Drought: a long period of unusually low rainfall.
Evaporation: the process by which liquid water changes into water vapour.
Urbanisation: the growth of towns and cities as more people move into them.
Pollution: contamination of the environment by harmful substances.
Sustainable management: using resources carefully so they remain available for future generations.
Water conservation: the careful use of water to reduce wastage.
Desalination: the process of removing dissolved salts from seawater to obtain freshwater.
NEWater: high-grade reclaimed water in Singapore made by purifying treated used water.
Microfiltration / ultrafiltration: a filtration process that removes suspended particles and some microorganisms.
Reverse osmosis: a process that forces water through a special membrane to remove dissolved substances and very tiny impurities.
Ultraviolet disinfection: the use of ultraviolet light to kill microorganisms in water.
Biodiversity: the variety of living organisms in a habitat or ecosystem.
Desertification: the process by which fertile land becomes dry and desert-like.

Worked Examples

Worked Example 1: Comparing total water and usable freshwater

Question type: Explain why water can still be scarce although Earth is covered by a lot of water.

Step-by-step answer

State the overall distribution of water:
- About 97% of Earth’s water is salt water.
- Only about 3% is freshwater.
Explain that most freshwater is not easily accessible:
- About 69% of freshwater is frozen in ice caps and glaciers.
- About 30% is underground as groundwater.
- Less than 1% is found in rivers and lakes.
Link to human use:
- Humans need accessible, clean freshwater for drinking, farming and industry.
- Only a very small amount is easily available.
Add that some available water is polluted:
- Pollution further reduces the amount of usable water.

Although Earth has a lot of water, about 97% of it is salt water and only about 3% is freshwater. Most freshwater is trapped in ice caps and glaciers or stored underground. Less than 1% of freshwater is found in rivers and lakes, which are easier for humans to use. In addition, some freshwater is polluted, so usable water is limited.

Worked Example 2: Identifying causes of water scarcity

Question type: A country has low rainfall, rapid population growth and polluted rivers. Explain why it may face water scarcity.

Step-by-step answer

Identify the physical factor:
- Low rainfall means less water enters rivers, lakes and reservoirs.
Identify the first human factor:
- Rapid population growth increases demand for water for drinking, sanitation and other uses.
Identify the second human factor:
- Polluted rivers reduce the amount of safe freshwater available.
Link all factors together:
- Supply is low, demand is high, and some water is unusable.

Model answer

The country may face water scarcity because low rainfall reduces the amount of water available in rivers and reservoirs. At the same time, rapid population growth increases demand for water. In addition, polluted rivers reduce the amount of safe freshwater that can be used. Therefore, the country has limited supply but high demand for water.

Worked Example 3: Explaining how Singapore manages water sustainably

Question type: Describe two ways Singapore manages its water supply sustainably.

Step-by-step answer

Choose two valid strategies:
- NEWater
- Desalination
Explain NEWater:
- Treated used water is purified by microfiltration/ultrafiltration, reverse osmosis and ultraviolet disinfection.
- It can be reused, reducing dependence on rainfall and imported water.
Explain desalination:
- Seawater is treated to remove salts.
- This provides a source of freshwater even when rainfall is low.
Link to sustainability:
- Both methods increase reliability of supply and reduce the risk of shortage.

Model answer

One way Singapore manages water sustainably is by using NEWater. Treated used water is further purified through microfiltration or ultrafiltration, reverse osmosis and ultraviolet disinfection. This allows water to be recycled and reused. Another way is desalination, where salts are removed from seawater to produce freshwater. These strategies help Singapore maintain a reliable water supply even though it has limited natural freshwater sources.

Common Mistakes to Avoid

Saying that all freshwater is easily available.
- Most freshwater is frozen or underground.
Confusing water scarcity with water pollution.
- Water pollution can cause water scarcity, but they are not the same thing.
Writing only one cause when the question asks for both physical and human factors.
Giving vague answers like:
- “not enough water”
- “people waste water”
- without explaining how these lead to scarcity
Forgetting to mention that salt water cannot be directly drunk without desalination.
Mixing up NEWater and desalinated water.
- NEWater comes from treated used water.
- Desalinated water comes from seawater.
Saying NEWater is simply “dirty water reused”.
- NEWater is high-grade reclaimed water that has gone through advanced purification.
Forgetting to link impacts to either people or the environment.
Writing “drought” as a human factor.
- Drought is a physical factor.
Describing water conservation only at the personal level and ignoring national strategies such as reservoirs, recycling and desalination.

Exam Tips

If asked about global distribution, include the key figures:
- 97% salt water
- 3% freshwater
- most freshwater in ice caps/glaciers and groundwater
If asked to explain water scarcity, use the phrase:
- “There is insufficient safe and accessible freshwater to meet demand.”
For causes, separate your answer into:
- physical factors
- human factors
This makes your answer clearer and helps earn marks.
When explaining a factor, always include the link to water supply or demand.
- Example: Population growth increases demand for water.
- Example: Drought reduces water stored in rivers and reservoirs.
For impact questions, use strong keywords:
- disease
- sanitation
- crop failure
- habitat loss
- biodiversity
- desertification
For sustainability questions, use the phrase:
- “ensures water is available for present and future generations”
For Singapore questions, know the exact terms:
- Four National Taps
- local catchment water
- imported water
- NEWater
- desalinated water
For NEWater, remember the treatment sequence:
1. microfiltration / ultrafiltration
2. reverse osmosis
3. ultraviolet disinfection
If comparing strategies, mention both advantages and possible limitations.
- Example: desalination provides reliable supply but is energy-intensive and costly.
Avoid informal words like “bad water” or “dirty stuff”.
- Use scientific terms such as:
  - polluted water
  - microorganisms
  - dissolved salts
  - water-borne diseases

Quick Summary

About 97% of Earth’s water is salt water; only about 3% is freshwater.
Most freshwater is stored in ice caps/glaciers and groundwater, so only a tiny amount is easily accessible.
Water scarcity means there is not enough safe and accessible water to meet needs.
Water stress happens when water demand is close to or greater than available supply.
Physical causes of water scarcity include low rainfall, drought, uneven rainfall and high evaporation.
Human causes include population growth, urbanisation, agriculture, industry, pollution and poor water management.
Water scarcity affects people through poor health, reduced sanitation, food shortage, loss of income and conflict.
Water scarcity affects the environment through drying water bodies, habitat loss, lower biodiversity and desertification.
Sustainable water management includes protecting catchment areas, reservoirs, recycling water, desalination, pollution control and conservation.
Singapore manages water using the Four National Taps: local catchment water, imported water, NEWater and desalinated water.
NEWater is produced by microfiltration/ultrafiltration, reverse osmosis and ultraviolet disinfection.
Water conservation in Singapore includes public education, efficient devices, fixing leaks and careful use of water.