Numerical Analysis of Flow and Transport from Trickle Sources on a Spatially Heterogeneous Hillslope

The purpose of the present study was to analyze movement and spreading of water and a passive solute (chloride) on a hillslope under surface drip irrigation, taking into account the texture of the soil, the slope of the terrain, the spatial heterogeneity of the soil hydraulic properties, and water extraction by plant roots. Results of the present investigation suggest that under surface drip irrigation, the movement and spread of water and solutes are affected mostly by the soil texture and less by the terrain slope. Increasing terrain slope is shown to increase the deflection of the trajectories of the centroid of the solute mass from the vertical axis, particularly in fine-textured soils associated with low saturated conductivity and considerable capillary forces, in which the interaction between adjacent drip line laterals may be appreciable. Transient flows originating from periodic water application and water uptake by plant roots are shown to enhance the effect of the terrain slope on water flow and solute movement, particularly in fine-textured soils. Implications regarding the problem of sensor placement with respect to drip irrigation management are briefly discussed.