Water losses through the bunds of irrigated rice fields interpreted through an analogue model

Abstract In many countries where rice is grown by basin irrigation, under continuous flow and with a ground water table at depths of 1 m or greater, field water use efficiencies of only 25–30% are measured. The principal loss is caused by lateral percolation, the movement of water from the flooded fields laterally into the bunds and thence vertically down to the water table. Typical field evidence is quoted, and water movement in the vicinity of the field boundary is studied by means of a resistance network analogue computer. The results show that field water use efficiencies can be greatly increased by sealing the bunds or by maintaining the shallowest possible water layer in the rice fields.