The big idea: Water, food and energy are not separate problems -- they are linked in a system called the nexus.
You cannot secure one without affecting the others:
- Growing food needs water and energy. - Producing energy needs water (cooling, hydropower) and sometimes land that could grow food. - Supplying clean water needs energy to pump, treat and move it.
So a decision in one part of the nexus has knock-on effects in the other two.
Key terms
- Nexus -- a set of connections where the three resources interact and depend on each other.
- Resource security -- having reliable, affordable access to enough water, food and energy.
- Trade-off -- gaining one resource at the cost of another (e.g. more biofuel = less food).
- Interdependence -- the resources rely on each other, so a change in one shifts the others.
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
How this is tested: Paper 2 asks you to Outline or Suggest a single interaction -- for example, how securing water can reduce food, or how energy choices use water. You must show the link, not just name two resources.
| Action to secure... | Effect on the other resources |
|---|---|
| Water (dams, irrigation) | Reservoirs need energy to pump; large dams can flood farmland; irrigation can cut river flow downstream. |
| Food (more farming) | Agriculture uses about 70% of the world's freshwater and needs fuel and fertiliser (energy) to grow and transport. |
| Energy (biofuels, hydro, cooling) | Biofuel crops take land and water from food; hydropower and power-plant cooling both rely on large amounts of water. |
Three interactions to remember
- Water -> food: irrigation grows crops, but over-pumping rivers and aquifers leaves less water for farms downstream.
- Energy -> water: thermal and nuclear power stations need huge volumes of water for cooling; if water is short, power output falls.
- Food -> energy: growing crops for biofuel (e.g. maize for ethanol) takes farmland and water away from food.
Suggest two ways in which securing a country's water needs can end up reducing the food available to grow.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Never wonder what to study next
Get a personalized daily plan based on your exam date, progress, and weak areas. We'll tell you exactly what to review each day.
Named examples (use these in essays): Top marks need named, real places. These show the nexus stretched by climate, population and choices.
Case studies
- The Nile basin -- Ethiopia's large hydropower dam stores water to make electricity, but Egypt downstream fears less river water for its farms, a clear energy-water-food clash between countries.
- California, USA -- long droughts force farmers to pump groundwater for food; pumping and moving that water uses large amounts of energy, and the aquifers are falling.
- The Aral Sea region -- decades of diverting rivers to irrigate cotton (food/cash crop) shrank the sea, ruining fisheries and the local climate.
- India's Punjab -- cheap subsidised energy lets farmers pump groundwater for food almost for free, so the water table is dropping fast.
Why the pressure is rising: A growing population and higher incomes demand more of all three resources at once, while climate change shifts rainfall and raises temperatures -- so the nexus is squeezed harder every decade.
How this is tested: A bar chart of water use by sector is a common stimulus here -- read the key, then Outline or Suggest an interaction before the longer essay. The big write-up is a [10] 'To what extent' asking how far one driver (climate change, or safe water) shapes the nexus, argued both sides with named examples and a judgement.
Read the key first. Which sector uses the most freshwater, and roughly what share?
Interactive diagram
Explore the labelled diagram, charts and maps for this topic in full study mode.
Using the chart, estimate the share of freshwater used by agriculture and state which sector uses the least.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
| Action to secure... | Effect on the other resources |
|---|---|
| Water (dams, irrigation) | Reservoirs need energy to pump; large dams can flood farmland; irrigation can cut river flow downstream. |
| Food (more farming) | Agriculture uses about 70% of the world's freshwater and needs fuel and fertiliser (energy) to grow and transport. |
| Energy (biofuels, hydro, cooling) | Biofuel crops take land and water from food; hydropower and power-plant cooling both rely on large amounts of water. |
IB-style question -- read the table
Using the table above: (a) outline one interaction between elements of the water-food-energy nexus [2]; (b) state which resource agriculture uses about 70% of [1].
How to answer each part
- (a) Outline one interaction. Pick one row and show the link both ways. E.g. securing energy with hydropower stores water behind a dam, which can flood farmland and cut river flow for farms downstream -- so an energy gain causes a food/water loss.
- (b) State the resource. The table says agriculture (food) uses about 70% of the world's freshwater -> the resource is water (freshwater).
Final answer
(a) one developed link, e.g. hydropower stores water but floods farmland / cuts downstream flow; (b) water (freshwater).
Discuss how far climate change is the single most important factor shaping the water-food-energy nexus.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.