Explain water distribution and water insecurity
Describe Earth's water stores and explain how physical and human factors affect access to sufficient clean water.
Exam scope and assessment notes
Original StudyForA teaching and practice, not Cambridge-authored questions, mark schemes or official grades. Cambridge expects candidates to study all eight topics, carry out investigative work and learn teacher-selected case studies. This course does not replace a centre's named case-study examples, current local environmental data, supervised fieldwork or the candidate's own investigation. Practice datasets are illustrative, not observations from a real place. No official assessment or certification is provided. The examples and practice datasets in these lessons are fictional and formative; learners must add their centre's verified case studies and current local evidence.
Before you begin
- Cambridge recommends prior environmental/science study equivalent to IGCSE or O Level. This is an AS-only qualification; use the exam-year syllabus and confirm centre entry details.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What makes environmental evidence useful?
What you will learn
- Describe salt, surface fresh, subsurface and atmospheric water
- Define water security and distinguish it from water volume
- Explain physical, infrastructure and social causes of water insecurity
Water stores are not equally accessible
Earth's water includes ocean salt water; surface fresh water in ice sheets, glaciers, lakes, rivers, swamps, marshes and permafrost; subsurface fresh water in soil moisture, groundwater and permafrost; and atmospheric water. Usable supply depends on location, season, quality, infrastructure and demand.
Water security means being able to access sufficient quantities of clean water for food and manufacturing, adequate sanitation and sustainable healthcare. Water may exist in a region while households still lack safe or reliable access.
Insecurity has linked causes and impacts
Causes in the syllabus include climate-driven rainfall change, drought and flooding, pollution events, inadequate sanitation, population growth, land-use change including deforestation and urbanisation, competing agricultural, industrial, energy and domestic demands, irrigation mismanagement and salinisation, international competition, unequal regional availability and differences in safe-water access between urban and rural areas.
Impacts include lower crop yields or crop failure, livestock deaths, food shortages, malnutrition and famine, and diarrhoea or cholera from contaminated drinking water. A case study should name the region, pressures, groups affected and dated evidence; a national average can hide unequal access.
Sources for this lesson
Pause and explain
What is the difference between water availability and water security?
Worked example
A region has high annual rainfall but recurring household shortages. Explain three possible mechanisms.
Show the worked solution
- Check seasonality and storage.
- Check pollution, treatment and distribution.
- Consider demand, affordability and inequality.
Answer Annual rainfall can hide long dry seasons when storage is inadequate. Pollution may make water unusable and leaking or absent pipes limit delivery. Demand growth or affordability barriers can also leave households insecure despite high rainfall.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A city faces shortages after a wet season. Name two infrastructure explanations and data that could test them.
Give me a hint
Rainfall timing and reliable delivery matter.
Compare my reasoning
- Identify the relevant data, place or process in the prompt.
- Apply describe salt, surface fresh, subsurface and atmospheric water to the stated context.
- Explain the inference and one limitation or trade-off.
Storage may be too small to carry water into the dry season, or leakage and treatment capacity may limit usable supply. Reservoir levels, groundwater, system losses, treatment output and interruption records can be compared with demand.
Look for these in your work
- Describe salt, surface fresh, subsurface and atmospheric water
- Uses relevant evidence and explains the environmental mechanism
- Distinguishes observation, inference and limitation
A river has high volume but faecal contamination. Is the region water-secure?
Give me a hint
Quantity and quality both matter.
Compare my reasoning
- Identify the relevant data, place or process in the prompt.
- Apply define water security and distinguish it from water volume to the stated context.
- Explain the inference and one limitation or trade-off.
High volume does not establish water security when water is contaminated. Safety, treatment capacity, reliable access, sanitation and household/service needs matter; the source may be unusable without effective treatment.
Look for these in your work
- Define water security and distinguish it from water volume
- Uses relevant evidence and explains the environmental mechanism
- Distinguishes observation, inference and limitation
A report says 90% of residents have improved water access. What should a regional study check?
Give me a hint
Disaggregate by location, reliability, quality and affordability.
Compare my reasoning
- Identify the relevant data, place or process in the prompt.
- Apply explain physical, infrastructure and social causes of water insecurity to the stated context.
- Explain the inference and one limitation or trade-off.
Check the indicator definition and reporting year. Compare urban and rural access and affected groups; measure continuity, quality and collection time. A national percentage can hide severe local shortages.
Look for these in your work
- Explain physical, infrastructure and social causes of water insecurity
- Uses relevant evidence and explains the environmental mechanism
- Distinguishes observation, inference and limitation
Common mistakes
- Equating rainfall with safe access
- Ignoring groundwater and seasonal storage
- Using a national average to represent unequal communities
What can you explain now?
What is the difference between water availability and water security?
Compare with the explanation
Security includes reliable access to sufficient clean water for people and services
Water can be present but polluted, inaccessible or unaffordable.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Why is high water volume alone insufficient to establish water security?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.