Introduction
Water pollution is one of the most pressing global environmental issues, and in IB Environmental Systems and Societies (ESS), it plays a central role in the 2026 first assessment. Students are expected to understand not only the types and causes of pollution, but also how pollution impacts ecosystems, societies, and sustainability.
This topic often appears in exams because it allows for systems thinking: linking pollution sources, impacts on biodiversity, human health consequences, and management strategies. To score highly, you need to go beyond definitions—using examples, evaluations, and case studies to demonstrate applied knowledge.
Quick Start Checklist for ESS Students
When revising water pollution for ESS, you should be able to:
- Define different types of water pollution.
- Identify sources (point vs. non-point).
- Explain impacts on ecosystems and human health.
- Use case studies to illustrate consequences.
- Evaluate management and prevention strategies.
Types of Water Pollution in ESS
1. Organic Pollution
- Sources: sewage, animal waste, food processing industries.
- Impacts: increases Biochemical Oxygen Demand (BOD), reduces dissolved oxygen, kills aquatic life.
- Example: untreated sewage in the Ganges River, India.
2. Nutrient Pollution (Eutrophication)
- Sources: agricultural runoff (nitrates, phosphates), detergents.
- Impacts: algal blooms, hypoxia, “dead zones.”
- Example: Gulf of Mexico Dead Zone caused by Mississippi River runoff.
3. Chemical Pollution
- Sources: pesticides, heavy metals, industrial discharge.
- Impacts: bioaccumulation, biomagnification, poisoning of species.
- Example: Minamata Bay (Japan) mercury poisoning.
4. Thermal Pollution
- Sources: power plants releasing hot water.
- Impacts: reduces dissolved oxygen, alters aquatic species composition.
- Example: impacts of nuclear power station outflows.
5. Plastic and Solid Waste Pollution
- Sources: plastics, microplastics, litter.
- Impacts: ingestion by marine life, disruption of ecosystems.
- Example: Pacific Garbage Patch.
6. Oil Spills
- Sources: tanker accidents, drilling leaks.
- Impacts: coats birds and marine mammals, reduces light penetration.
- Example: Deepwater Horizon (2010).
Point vs. Non-Point Sources
ESS requires you to distinguish between:
- Point sources: identifiable, single sources (e.g., factory discharge pipe).
- Non-point sources: diffuse, harder to control (e.g., agricultural runoff).
This distinction is common in exam questions.
Impacts of Water Pollution
Environmental
- Biodiversity loss.
- Disruption of food chains through bioaccumulation.
- Habitat destruction in rivers, lakes, and oceans.
Social and Health
- Spread of cholera and typhoid from sewage.
- Reduced drinking water safety.
- Decline in fisheries, impacting livelihoods.
Economic
- Costs of water treatment.
- Collapse of tourism in polluted areas.
- Reduced agricultural productivity from contaminated irrigation.
Management Strategies
Prevention
- Legislation limiting industrial discharge.
- Sustainable farming to reduce runoff.
- Wastewater treatment facilities.
Clean-Up and Restoration
- Aeration of lakes to improve dissolved oxygen.
- Oil spill containment and clean-up.
- Plastic waste removal projects.
Education and Awareness
- Community-led cleanup campaigns.
- Promoting reduced use of harmful chemicals.
Case Studies for ESS Exams
- Ganges River (India): cultural, religious, and pollution pressures combined.
- Aral Sea (Central Asia): ecosystem collapse due to mismanagement.
- Gulf of Mexico Dead Zone: eutrophication case study.
- Minamata Bay (Japan): chemical pollution tragedy.
Water Pollution in ESS Exams
Paper 1
Case study booklets often feature water pollution, with maps or graphs showing nutrient levels, dissolved oxygen, or biodiversity indices.
Paper 2
Possible essay questions include:
- “Evaluate the impacts of eutrophication on aquatic ecosystems.”
- “Distinguish between point and non-point sources of water pollution with examples.”
Exam Tips
- Always specify type + impact + example.
- Use the point vs. non-point distinction—examiners love it.
- Balance solutions—show both prevention and clean-up measures.
FAQs
1. Do I need to memorize every type of pollution?
You should focus on the main categories (organic, nutrient, chemical, thermal, plastic, oil). Know at least one example for each.
2. How detailed should case studies be?
You don’t need dates or statistics, but a named location plus a specific impact is essential.
3. Could water pollution appear as a data response question?
Yes. Graphs showing changes in dissolved oxygen or BOD are common. You may be asked to interpret trends and explain ecological impacts.
Conclusion
Water pollution is a cornerstone of the ESS syllabus because it links ecosystems, human health, and sustainability. To score highly, know the main types of pollution, distinguish point and non-point sources, and apply case studies. By combining strong definitions with evaluation of management strategies, you’ll be fully prepared for exam questions on this topic in the 2026 first assessment.
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