|Warrick, Authur - University Of Arizona|
Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2014
Publication Date: 5/22/2014
Citation: Bautista, E., Warrick, A.W., Strelkoff, T. 2014. New results for an approximate method for calculating two-dimensional furrow infiltration. Journal of Irrigation and Drainage Engineering. 140(10):04014032
Interpretive Summary: major challenge to the hydraulic analysis of furrow irrigation systems is modeling the two-dimensional infiltration process. Most simulation models and practical procedures for the design and evaluation of furrow irrigation systems rely on empirical infiltration equations. Those formulations generally ignore the combined effect of variable wetted perimeter and flow depth on the infiltration process, although some attempt to account for wetted perimeter variations. Those combined effects are accounted with the two-dimensional form of the Richards. Because of the highly non-linear nature of the equation, those computations can fail to converge or can produce large mass balance errors. For irrigation modeling purposes, simpler and more robust computations are needed. An approximate solution to the two-dimensional Richards equation was proposed by Warrick et al.(2007). The equation computes infiltration as the sum of one-dimensional infiltration and a term labeled the edge effect, which varies linearly with time. This study expands on Warrick's concept, with the objective of better understanding the role of wetted perimeter and water pressure on the edge effect. The study also explores how the concept is affected by the selection of soil hydraulic model. The original concept was developed using the van Genuchten model and the Brooks-Corey model is tested as an alternative. The study aims to provide additional guidance for calibration of the method for specific soil and flow conditions. Thus, it should be of interest to professionals interested in modeling infiltration based on physical principles.
Technical Abstract: Warrick et al. (2007) proposed an approximate solution following the two-dimensional Richards equation, which can be used to estimate furrow infiltration based on soil physical properties. The equation computes infiltration as the sum of one-dimensional infiltration and a term labeled the edge effect, which varies linearly with time. The edge effect is a function of sorptivity, soil water content, and an empirical parameter ' which requires calibration for the specific soil and flow conditions. This study expands on Warrick's concept. The objectives were to better understand the role of wetted perimeter and water pressure on the edge effect, to examine the role played by the soil hydraulic model in determining the value of the ' parameter, and to provide additional guidance for calibration of the method for specific conditions. Results show that the range of variation for ' depends on the pressure used for one-dimensional and edge effect calculations, and that this range can be reduced by using the wetted-perimeter averaged flow depth. Results also suggest differences in the value of ' depending on whether soil hydraulic properties are described with the van Genuchten or Brooks-Corey soil hydraulic models.