Unsaturated soil water movement in hysteretic and water repellent field soils

Both hysteresis and preferential flow affect soil water movement in the unsaturated zone. The agrohydrological numerical model in which these two processes have been included was applied to data sets from two sites with hysteretic and water-repellent soils. It was found that hysteresis retards soil water movement, whereas preferential flow enhances it. In fields with shallow water-tables and without ponding, soil water fluxes are marginally affected by hysteresis and preferential flow. Preferential flow, however, directly affects the residence time of solutes in the unsaturated zone.