Agriculture and water
Seventy percent of global withdrawal, most of it consumed rather than returned — and the efficiency measures that seem obvious frequently do not work as expected.
Agriculture withdraws roughly 70% of the world’s fresh water, and consumes a higher share still — irrigation water is largely transpired by crops and evaporated from soil, so it leaves the catchment rather than returning to it. Any serious conversation about water use is mostly a conversation about farming.
A high agricultural share reflects the size and irrigation intensity of the farming sector rather than inefficiency. Countries at the top of any such ranking are typically food producers in arid regions.
View the data behind this chart
| Subject | Value (%) | Notes |
|---|---|---|
| Somalia | 99.5 | — |
| Afghanistan | 98.2 | — |
| Nepal | 98.1 | — |
| Mali | 97.9 | — |
| Sudan | 96.2 | — |
| Laos | 95.9 | — |
| Madagascar | 95.9 | — |
| Vietnam | 94.8 | — |
| Eritrea | 94.5 | — |
| Guyana | 94.3 | — |
| Eswatini | 94.2 | — |
| Bhutan | 94.1 | — |
| Cambodia | 94.0 | — |
| Pakistan | 94.0 | — |
| Turkmenistan | 92.7 | — |
| Kyrgyzstan | 92.7 | — |
| Azerbaijan | 92.2 | — |
| Iran | 92.2 | — |
| Uzbekistan | 92.1 | — |
| Ethiopia | 91.8 | — |
| Timor-Leste | 91.4 | — |
| Senegal | 91.3 | — |
| Niger | 91.0 | — |
| Chile | 90.9 | — |
| Yemen | 90.7 | — |
How irrigation water is actually used
Only a fraction of the water applied to a field is transpired by the crop. The rest evaporates from the soil surface, percolates below the root zone, or runs off the end of the field. Field application efficiency ranges from roughly 50% for surface flood irrigation to over 90% for well-managed drip.
The irrigation efficiency paradox
This does not mean drip irrigation is a bad idea — it raises yields, reduces energy use for pumping and cuts salinisation. It does mean that installing it does not, by itself, leave more water in the river, and policies that assume otherwise have repeatedly failed to deliver the savings they promised.
Groundwater and the pump
Roughly 40% of global irrigated area is groundwater-fed. Where electricity for pumping is subsidised or unmetered, the marginal cost of another cubic metre is close to zero — which is the underlying economics of groundwater depletion in northern India, the North China Plain and the western United States.
The resulting problem is a classic common-pool one: each individual well has an imperceptible effect, the collective effect is severe, and every abstractor faces an incentive to pump before their neighbours do. Solving it requires either metering and pricing, or enforceable collective limits — both politically difficult.
Water quality, not just quantity
- Nitrate leaching to groundwater, which takes decades to arrive and decades to clear
- Phosphorus carried on eroded soil into watercourses, driving eutrophication
- Pesticides and their metabolites, regulated in Europe at a precautionary 0.1 µg/l
- Salinisation, where irrigation in arid regions concentrates salts in the soil — the mechanism that has degraded irrigated land since Mesopotamia
- Sediment from bare soil, which smothers spawning gravels
Sources
- Food and Agriculture Organization of the United Nations — AQUASTAT — Global Information System on Water and Agriculture. Public but restricted · CC BY-NC-SA 3.0 IGO
- UNESCO World Water Assessment Programme — United Nations World Water Development Report. Open — attribution required · CC BY-SA 4.0
- Central Ground Water Board — Indian groundwater resource assessment. Open — attribution required · Government Open Data License – India