Changing demands for water from human activities: agriculture
Trends in Water Consumption: Agriculture
What You’ll Learn
🌾 Agriculture is the biggest user of freshwater worldwide. We’ll explore how demand changes, why it matters, and how it’s measured.
- Water use per hectare: $W = \dfrac{V}{A}$
- Key crops and their water footprints
- Technological and climate drivers
- Exam‑ready facts and figures
Water Use in Crops
Think of a farm as a giant water‑sponge. The amount of water it needs depends on the crop, soil, and climate. Here’s a quick snapshot:
| Crop | Water Use (m³/ha) | Typical Irrigation Method |
|---|---|---|
| Rice | 10,000–12,000 | Flooded paddies |
| Wheat | 4,000–6,000 | Drip or sprinkler |
| Corn | 6,000–8,000 | Sprinkler |
💡 Analogy: Imagine each crop as a different sized plant in a garden. Some plants (like rice) need a lot of water, while others (like wheat) are more drought‑tolerant.
Factors Driving Change
- Population Growth – More mouths to feed means more crops, so more water.
- Dietary Shifts – Meat‑heavy diets require more feed crops, increasing water demand.
- Climate Change – Drier summers push farmers to irrigate more often.
- Technology – Drip irrigation can cut water use by up to 50% compared to flood irrigation.
- Policy & Subsidies – Water‑efficient practices are often incentivised.
Case Study: Rice in Asia
Rice paddies are the classic example of high water use. In 2020, Asia used about 70% of the world’s irrigation water for rice. However, new submerged irrigation techniques can reduce water use by 30% while keeping yields stable.
📈 Trend: From 1990 to 2020, rice water use per hectare fell from 12,000 m³ to 9,000 m³ in many regions, thanks to improved irrigation.
Exam Tips
🔍 Remember: Distinguish between irrigation water (water applied to crops) and total water consumption (includes domestic, industrial, and ecological).
📌 Key terms to know: water footprint, irrigation efficiency, water‑use intensity, evapotranspiration.
📝 Practice question: “Explain how drip irrigation can reduce water consumption in a semi‑arid region.” Write a short paragraph, using at least one equation.
💬 Tip: Use analogies (e.g., “like a sponge”) to explain concepts quickly in your answer.
Revision
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