The effect of hysteresis on three-dimensional transient water flow during surface trickle irrigation

The effect of hysteresis on deep percolation, irrigation efficiency and soil water content profiles by surface point sources was studied through the use of a cylindrical flow model which incorporates hysteresis in the soil water characteristic curve (Scott et al., 1983), evaporation from the soil surface and water extraction by roots. Several combinations of discharge rate and irrigation durations were tested. The dripper spacing was 60 x 60 cm. The implementation of the mathematical model took place against two of the twelve USDA soil classes. Water content profiles are presented for a radial distance of 1, 17 and 32.8 cm from the point source and for various times. The results show that hysteresis seems to reduce the water losses under the root zone at the end of the simulation time to a great extent. In addition, it was found that hysteresis reduced the deep percolation more in the coarse-grained soil than in the fine-grained soil. Finally, for both soils hysteresis increased the irrigation efficiency. Copyright (c) 2008 John Wiley & Sons, Ltd.