|Warrick, Arthur - University Of Arizona|
Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2015
Publication Date: 7/29/2015
Citation: Bautista, E., Warrick, A.W. 2015. Closure to new results for an approximate method for calculating two-dimensional furrow infiltration. Journal of Irrigation and Drainage Engineering. DOI:10.1061/(ASCE)IR.1943-4774.0000753.
Interpretive Summary: In a discussion paper, Ebrahimian and Noury (2015) raised several concerns about an approximate physically-based, furrow infiltration model proposed by Bautista et al. (2014). Such a model is of practical interest for purposes of predicting infiltration with a furrow irrigation modeling system. A key concern is that part of the analysis contrasts results developed with two different soil hydraulic models, but comparisons are for broad soil textural categories and not for specific soils. This closure paper argues that comparisons based on the same soil will still produce different results because the assumed soil hydraulic model has a profound impact on the predicted infiltration behavior. This is demonstrated in the original paper with one example where the two models are used to represent the hydraulic properties of the same soil. Thus, comparisons based on broad soil textural categories are still useful for understanding how the selected soil hydraulic model impacts the approximate furrow infiltration model.
Technical Abstract: In a discussion paper, Ebrahimian and Noury (2015) raised several concerns about an approximate solution to the two-dimensional Richards equation presented by Bautista et al (2014). The solution is based on a procedure originally proposed by Warrick et al. (2007). Such a solution is of practical interest for purposes of modeling infiltration in furrow irrigation systems. A key concern is that part of the analysis contrasts results developed for soils represented with the van Genuchten and the Brooks-Corey soil hydraulic models. The approximate solution requires an empirical parameter and the range of values for that parameter is slightly different depending on the model used to represent the soil hydraulic properties. In the analysis, most tests were conducted with different soils for each soil hydraulic model. The discussers argued that comparisons should have conducted using the same soil for each soil hydraulic model. One such case is included in the original paper. This closure paper argues that the assumed soil hydraulic model has a profound impact on the infiltration behavior predicted with the Richards equation, even for the same soil. Thus, the assumed soil hydraulic model affects the calibration of the approximate solution, separately from the soil texture. This is demonstrated in the original paper with one set of tests involving the same soil, but with the two hydraulic models. Results generated with each soil hydraulic model were consistent with those generated with other soil textures but the same hydraulic model. This shows that comparisons based on broad soil textural categories are still useful for understanding how the selected soil hydraulic model impacts the approximate solution.