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Approximate furrow infiltration model for time-variable ponding depth

E. Bautista, A. W. Warrick, J. L. Schlegel, K. R. Thorp, D J. Hunsaker
Journal of Irrigation and Drainage Engineering 2016 v.142 no.11 pp. 1-11
Richards' equation, furrow irrigation, furrows, geometry, hydrologic models, infiltration (hydrology), soil hydraulic properties, water flow
A methodology is proposed for estimating furrow infiltration under time-variable ponding depth. The methodology approximates the solution to the two-dimensional Richards equation, and is a modification of a procedure that was originally proposed for computing infiltration under constant ponding depth. Two computational approaches were developed and tested using several combinations of soil hydraulic properties, furrow geometry, and flow depth variations. Both methods yielded solutions of reasonable and similar accuracy relative to numerical solutions of the two-dimensional Richards equation. The analysis also showed that the accuracy of the approximate model varies mostly as a function of soil hydraulic properties. The accuracy of the approximate solution can be improved with calibration. Two calibration methods were examined, one assuming that the calibration parameter varies with depth, and the other assuming a constant value. The analysis showed that latter approach, in combination with one of the proposed computational methods, reproduced the Richards equation solution more accurately. This means that a unique calibration parameter can be developed for the particular soil and geometric configuration conditions, and applied to different patterns of ponding depth variation.