Basin Irrigation

1. The field is levelled and divided into basins enclosed by low bunds
2. Water is delivered to each basin from a channel, pipe, or field ditch
3. The basin fills to a shallow depth and the inflow is then stopped
4. Ponded water infiltrates into the soil across the whole basin area
5. For flooded rice, a water layer is deliberately maintained rather than allowed to fully drain

Basin irrigation suits land that is level or can be levelled, and soils of medium to heavy texture that hold water well. Heavier soils such as clays and vertisols retain the ponded water rather than losing it rapidly downward, which makes them well matched to the method. It is particularly associated with lowland rice, where a ponded layer suppresses weeds and suits the crop.

Because water covers and is held on the whole surface, basin irrigation can lose water to evaporation and, on lighter or less level land, to deep percolation beyond the root zone. Precise land levelling, appropriately sized basins, and a large enough inflow to fill each basin quickly all improve how evenly and efficiently water is applied. Laser-guided levelling has improved uniformity where it is available.

Prolonged ponding can also raise water tables and contribute to waterlogging or salinity problems where drainage is poor, so basin systems are managed together with adequate drainage.

Basin irrigation is valued for its low equipment cost and simplicity, needing no pressurised network, but it demands careful land preparation and a reliable, sufficient water supply to fill basins evenly. In water-scarce settings, rice basin systems in particular are a focus of water-saving practices that reduce continuous flooding.