Surface water storage independent equation for predicting furrow irrigation advance

A simple equation is developed to predict the advance rate of flow in furrows. The proposed equation does not use as inputs the data required for estimating the surface storage. In previous surface storage independent models it is generally assumed that the surface storage volume is negligible (compared with infiltrated volume). The proposed equation is derived by eliminating the surface storage term from the original volume balance equation and its derivative. The suggested equation thus needs no assumption about the magnitude of the value of surface storage volume. Infiltration is described by the extended Kostiakov-Lewis formula. The suggested equation is compared with observed furrow data, with the numerical kinematic-wave model and with a recently developed numerical model that ignores surface storage. For furrows in which the surface storage is not significant (compared with infiltration) all models predict advance reasonably well. For furrows in which the surface storage is relatively important, the proposed equation predicts advance with good accuracy, whereas previous models ignoring the surface storage greatly overpredict the advance rate.