The big idea: Water scarcity is when there is not enough fresh water to meet people's needs. It is usually measured per person per year (m3 per capita).
Geographers split it two ways. Physical (absolute) scarcity is when the natural supply itself is too small — a dry climate or a low water table. Economic scarcity is when the water exists but people cannot reach it — they lack the money, pipes, pumps or institutions to deliver it.
Most data-response questions ask you to read availability figures off a graph and decide whether a country is stressed; the essay asks you to weigh physical against economic causes.
Key terms for water scarcity
- Water scarcity — not enough fresh water to meet demand (measured per person per year).
- Water stress — supply is under 1 700 m3 per person per year (the Falkenmark stress line); demand starts to strain supply.
- Physical (absolute) scarcity — the natural supply itself is too small (dry climate, low rainfall, low water table).
- Economic scarcity — water exists but a lack of money, infrastructure or institutions stops people reaching it.
- Aquifer — an underground rock store of groundwater; over-abstraction is pumping it faster than it refills.
- Drought — a long, abnormally dry period that cuts the available supply.
The Falkenmark thresholds: Below 1 700 m3 per person per year = water stress. Below 1 000 m3 = water scarcity. Below 500 m3 = absolute scarcity. Learn these three numbers — a data question often asks you to classify a country from its figure.
How this is tested: Paper 1 Option A opens with a data-response on a graph, map or table of water data. You State or Identify a value (a count, a named country, the biggest change), or Describe a spatial distribution off a map. Read carefully, quote units (m3 per person per year), and for a map use latitude/longitude or named regions, never 'top-left'.
| Country | 1990 | 2020 | Change | 2020 status |
|---|---|---|---|---|
| Country P | 2 400 | 1 550 | -850 | Stress |
| Country Q | 1 900 | 950 | -950 | Scarcity |
| Country R | 2 700 | 1 200 | -1 500 | Stress |
| Country S | 800 | 430 | -370 | Absolute scarcity |
| Country T | 5 200 | 4 600 | -600 | No stress |
Classify a country from its figure: Compare each country's value to the Falkenmark lines: below 1 700 = stress, below 1 000 = scarcity, below 500 = absolute scarcity. To find the biggest drop, subtract each country's later value from its earlier value and compare the differences.
Describe = pattern, not a list: If asked to Describe a distribution on a map, give the overall pattern plus located detail — use latitude/longitude bands or named regions (e.g. concentrated around 20 deg N in the dry tropics), and quote anomalies. Marks are lost for 'in the top corner'.
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Scarcity has two kinds of cause. Physical causes shrink the natural supply: low or seasonal rainfall, drought, a rain shadow, falling water tables, or cold ocean currents that bring dry air. Economic causes mean the water is there but unreachable: no money for pipes, pumps, dams or treatment, weak institutions, or rapidly rising demand from population growth and irrigation.
| Type | Examples | What it means |
|---|---|---|
| Physical (absolute) | Low rainfall, drought, rain shadow, falling water table, El Nino/La Nina | The natural supply itself is too small |
| Economic | No money for pipes/pumps/dams, weak governance, poverty | Water exists but people cannot reach it |
| Rising demand | Population growth, irrigation, industry, cities | Demand outpaces a fixed supply, deepening stress |
| Over-abstraction | Pumping aquifers faster than they recharge | A short-term fix that worsens long-term physical scarcity |
Impacts of aquifer over-abstraction
- Falling water table — wells and springs run dry, so rivers and lakes fed by groundwater shrink.
- Ground subsidence — the land sinks as emptied pore spaces collapse, cracking buildings and roads.
- Saltwater intrusion — near coasts, seawater seeps into the emptied aquifer and pollutes the supply.
Real cases of scarcity: Physical scarcity grips the Sahel of West Africa, where low and erratic rainfall and recurring drought leave little surface water. Economic scarcity dominates much of rural sub-Saharan Africa, where rivers and groundwater exist but villages lack the boreholes, pipes and funds to use them. Over-abstraction is draining the Ogallala Aquifer under the US High Plains and has caused parts of Jakarta to subside as its groundwater is pumped out.
Drought turns stress into crisis: A drought is a long, unusually dry spell that sharply cuts supply. It hits farming hardest: crops fail, yields and livestock fall, so farmers lose income, food prices rise and people may migrate. Drought is a physical trigger, but its impact depends on economic capacity — a rich basin with reservoirs and irrigation copes far better than a poor one, which is why the physical-versus-economic debate sits at the heart of this topic.
How this is tested — the [10] essay: Paper 1 Option A ends with a 10-mark essay, marked on markbands. The recurring version asks to what extent physical factors, rather than economic ones, drive water scarcity.
Top band needs: accurate terms, developed physical AND economic causes with named examples, a weighing of their relative importance across places/scales, and a clear, justified conclusion.