5.5 Irrigation Methods

Why irrigation methods matter

Agriculture uses most of the world's freshwater, so irrigation efficiency affects water availability and environmental health. Methods vary widely in how much water they deliver to crops versus how much is lost to evaporation, runoff, or seepage. Choosing efficient methods reduces water waste and land degradation.

Common irrigation methods

Flood (furrow) irrigation floods fields with water — cheap but very inefficient, causing runoff and waterlogging. Spray/sprinkler irrigation distributes water through overhead sprinklers — moderate efficiency but loses water to evaporation and wind drift. Drip irrigation delivers water directly to plant roots through tubes — most efficient (~90%+), but has high installation costs.

Environmental impacts of irrigation

Overirrigation can cause salinization (salt buildup as water evaporates, leaving minerals) and waterlogging, reducing soil fertility. It can also deplete aquifers and rivers, as seen with the Aral Sea and Ogallala Aquifer. Efficient methods like drip irrigation and practices like drip scheduling help conserve water and protect soil quality.

Key terms

Drip irrigation

Delivers water directly to plant roots via tubing; most water-efficient method (~90%+) but costly to install.

Flood (furrow) irrigation

Floods entire fields with water; low-cost but highly inefficient, causing runoff and waterlogging.

Sprinkler irrigation

Distributes water overhead like rain; moderate efficiency but loses water to evaporation and wind drift.

Salinization

Buildup of salts in soil from evaporating irrigation water, reducing soil fertility.

Aral Sea

A sea that dramatically shrank due to river diversion for irrigation, illustrating unsustainable water use.

Try an AP-style question

Which irrigation method is the most water-efficient?

1. Drip irrigation
2. Flood irrigation
3. Spray irrigation
4. Furrow irrigation