The use of high resolution electrical resistivity tomography (ERT) and mechanistic hydrological models to increase the efficiency of the wáter applied by irrigation.

Abstract

To improve the efficiency of irrigation water application it is necessary to understand 3 important aspects. The depth of wetting reached by each irrigation episode, the overlap between irrigation emitters and the depth where the largest root volume is found. The joint use of electrical resistivity tomography (ERT) with mechanistic hydrological model allows establishing an appropriate irrigation schedule for the particular condition of each irrigation sector, considering aspects for intra-farm soil variability and variations in the root volume of the orchard. For a correct characterization of the existing soil variability in a field, we propose the use of high-resolution ERT (several measurements per hectare) and clustering using k-means for the definition of sites of interest where it is necessary to obtain a petrophysical relationship. (Waxman & Smits, 1968) that allows obtaining the moisture content of the soil from the electrical resistivity of the soil. For the calibration of the mechanistic hydrological model in these same sites, the use of disk infiltrometers measurements is proposed. Through time-lapse ERT measurements in periods between irrigation, it is possible to observe areas of greater water absorption and define areas where there is a greater root volume. Through time-lapse ERT measurements in irrigation episodes, it is possible to determine the depth of wetting reached and use this information to calibrate model parameters of the mechanistic hydrological model. Finally, the use of computer simulations in the defined clusters makes it possible to establish irrigation times and frequencies that ensure a correct overlap between emitters and a wetting depth that reaches the areas of greatest water absorption.