Water access, desalination and multipurpose dams
Compare water availability, explain two desalination methods and evaluate the opportunities and trade-offs of dams.
Section Paper 1 · Principles of Environmental Management
This original StudyForA sequence supports Cambridge IGCSE Environmental Management 0680 Topics 1–4 for exams in 2027, 2028 and 2029. Named local examples are chosen by the learner and centre; verify current conditions and local context with reliable sources. It is not a Cambridge paper, official grade or complete course.
Before you begin
- Use the 2027–2029 syllabus and check your exam year and centre's entry arrangements. Topics 1–4 are taught on this page; Topics 5–7 are still being built.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which is a use of a multipurpose dam in the syllabus?
What you will learn
- Compare water availability, explain two desalination methods and evaluate the opportunities and trade-offs of dams.
- Use evidence from an unfamiliar case to compare options and justify a context-sensitive judgement.
Compare access rather than rainfall alone
Potable-water availability can differ between water-rich and water-poor regions, and between urban and rural areas. It also depends on treatment, infrastructure, cost, reliability and sewage services; access is not distributed equally worldwide.
Use the evidence in the question to separate physical water supply from access to water that is safe to drink. A region may receive rain but lack storage, treatment or a safe distribution network.
Compare desalination processes
In distillation, water is heated until it boils; salt remains in the liquid, steam is cooled and condensed to produce water. In reverse osmosis, high pressure pushes water through a membrane that allows water molecules through while stopping most ions and other molecules.
Desalination can supplement freshwater supply in suitable coastal settings, but requires energy, equipment and finance and creates concentrated brine that must be managed. Compare local demand, energy and environmental effects before recommending it.
Evaluate a multipurpose dam
A multipurpose dam can provide flood control, hydroelectric power, irrigation, water storage, transport, recreation, tourism and fish farming.
Benefits may include reliable supply or electricity, while limitations can include flooded land, changed river flows, displaced communities, habitat effects, sediment changes and high construction costs. The balance depends on site, design and who gains or bears the costs.
Sources for this lesson
Pause and explain
Why can water availability differ between urban and rural regions?
Worked example
A coastal city has limited freshwater and reliable electricity from renewable sources. Explain how reverse osmosis might help, one limitation to manage and two other uses a nearby multipurpose dam could provide.
Show the worked solution
- High pressure forces water through a membrane that passes water molecules while stopping most ions and other molecules.
- Energy needs, cost and brine disposal still need a plan; the coastal setting alone does not settle whether the system is suitable.
- A dam could store water and provide irrigation, hydroelectric power or flood control, among other uses.
Answer Reverse osmosis could add potable water by separating most dissolved ions through a membrane. Planners still need to evaluate energy, cost and brine effects. A multipurpose dam can support storage and other functions, but its impacts must also be assessed.
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 water-poor coastal region considers desalination. Compare distillation and reverse osmosis by describing the separation step in each.
Give me a hint
One heats and condenses water; the other uses pressure and a selective membrane.
Compare my reasoning
- Distillation boils water; salt stays in the liquid and the steam is condensed.
- Reverse osmosis applies high pressure so water passes through a membrane while most ions are retained.
- Both can produce potable water, but energy, cost and brine management still matter.
Distillation separates by evaporation and condensation; reverse osmosis separates under pressure through a membrane. Their suitability depends on resources and environmental management.
Look for these in your work
- Both processes distinguished
- Salt or ions accounted for
- At least one common limitation included
A dam proposal could store water, provide irrigation and generate hydroelectricity, but would flood a settlement and habitat. Write a balanced decision plan with two benefits, two costs and evidence needed.
Give me a hint
Include affected people and ecosystems, plus who receives the benefits.
Compare my reasoning
- Identify storage, irrigation and electricity as potential benefits, and state which groups would receive them.
- Consider displacement, loss of habitat, altered river conditions and construction cost as possible costs.
- Compare alternatives and mitigation using population, land, ecological, flow, economic and safety evidence before making a conditional judgement.
The dam may improve water storage and provide irrigation and electricity, but could displace people and alter habitat and river conditions. A decision needs evidence about affected communities, environmental flows, costs, alternatives and how benefits are shared.
Look for these in your work
- Two benefits and two costs included
- Distribution of benefits considered
- Evidence supports conditional judgement
Two rural districts receive similar rainfall, but one has treated reservoirs and maintained pipes while the other relies on distant wells and has limited sewage treatment. Explain why potable-water access may still differ.
Give me a hint
Distinguish amount of water from safe, accessible supply and sanitation.
Compare my reasoning
- Rainfall does not show whether water is stored, treated or delivered safely.
- Reservoirs and maintained pipes can make treatment and distribution easier, while distant wells may raise time, cost and reliability barriers.
- Sewage treatment affects public health and water quality; compare access and service evidence as well as rainfall.
The districts may have similar physical rainfall but different storage, treatment, distribution and sanitation. Potable access depends on infrastructure, distance, cost and safe management, not rainfall alone.
Look for these in your work
- Supply and access separated
- At least two infrastructure factors applied
- Sewage treatment considered
Common mistakes
- Assuming desalination removes every dissolved substance with no energy
- Equating water-rich with universal household access
- Listing dam benefits without considering displaced people or habitat
- Assuming any dam is automatically multipurpose
What can you explain now?
What happens during reverse osmosis?
Compare with the explanation
High pressure moves water through a membrane that blocks most ions
The correct answer is “High pressure moves water through a membrane that blocks most ions”. The alternatives “Salt is removed only by freezing the whole ocean” and “Water is filtered through a coarse screen only” do not match the syllabus concept. Compare water availability, explain two desalination methods and evaluate the opportunities and trade-offs of dams.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Compare desalination methods and state how to balance dam benefits with local social and environmental costs.
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.