Infiltration as a Dependent Variable in Modeling Furrow Irrigation

Most surface irrigation models assume that infiltration is independent of surface flow hydraulics. However, wetted perimeter has been shown to significantly affect infiltration in furrows. Furthermore, wetted perimeter is known to vary with respect to time and distance along the furrow during irrigation. Thus, to completely model the hydraulics of furrow irrigation, infiltration must be considered a dependent variable in the momentum and continuity equations of free surface flow. This paper outlines a surge/continuous flow furrow irrigation kinematic wave model in which infiltration is a dependent variable of the wetted perimeter and infiltration opportunity time is a function of the transverse and longitudinal location within the furrow. Field determination of infiltration, roughness, inflow hydrograph, and furrow geometry are inputs to the model.