Surface irrigation is a method of delivering water to crops by letting gravity move water over the soil surface. It is the most common form of irrigation worldwide and is often called flood irrigation, though many techniques within this category involve careful management to control water distribution. The water can cover the entire field or flow along specific paths, such as furrows, basins, or borders, depending on the system design and crop needs. Key phases in the process include the advance of water across the field, a wetting/ponding period, and the depletion and recession of water as it infiltrates the soil and drains.

Common surface irrigation methods

• Basin irrigation: water is ponded in depressions or basins to cover the root zone.
• Furrow irrigation: water flows along narrow channels between crop rows.
• Border strip (or border irrigation): water moves along the field as a continuous strip, wetting the crop along its length.
• Uncontrolled flooding: water spreads over the field with minimal guidance, typically used on flat, uniform soils.

Key considerations

• Gravity-driven flow: distribution depends on slope, infiltration rate, and field setup.
• Efficiency and management: while historically viewed as inefficient, proper practices (e.g., controlled inflow, surge irrigation, and proper field leveling) can improve efficiency and uniformity.

Why it matters

• Simplicity and low capital cost: surface irrigation relies on gravity and land shaping rather than complex equipment.
• Local suitability: works well where soils, slope, and water availability match the chosen surface method.