Modeling solute transport in sprinkler irrigation laterals

Authors: ZERIHUN, DAWITT - University Of Arizona; SANCHEZ, CHARLES - University Of Arizona; ROCK, CHANNAH - University Of Arizona; Williams, Clinton

Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2023
Publication Date: 12/20/2023
Citation: Zerihun, D., Sanchez, C., Rock, C., Williams, C.F. 2023. Modeling solute transport in sprinkler irrigation laterals. Journal of Irrigation and Drainage Engineering. 150(2). https://doi.org/10.1061/JIDEDH.IRENG-10176.
DOI: https://doi.org/10.1061/JIDEDH.IRENG-10176

Interpretive Summary: Applying fertilizer in irrigation water is a cost effective method for applying needed nutrients that can help reduce production costs and mitigate environmental effects of agricultural chemicals. Solute transport-reaction models can be used as inexpensive and convenient management tools for agricultural chemical application systems. As a step towards the development of a field-scale sprinkler irrigation chemigation systems management model, a solute transport model that can simulate concentration of a nonreactive solute in an irrigation lateral is developed and evaluated. Solute transport is modeled as a one-dimensional advective process. Solutions to the transport problem, in a pair of consecutive pipes, are coupled. The model was tested through comparison of model outputs with analytical solutions. Evaluation of the predictive capacity of the model in a real-world application was then conducted by comparing computed breakthrough curves of a nonreactive tracer with data measured along a pair of laterals. The results suggest that model performance is satisfactory.

Technical Abstract: The application of agricultural chemicals to crops in the form of aqueous solutions or emulsions blended with irrigation water (often referred to as chemigation) is widely practiced in modern farming systems. Effective management of chemigation systems can help reduce production costs and mitigate environmental effects of agricultural chemicals. Solute transport-reaction models can be used as inexpensive and convenient management tools for agricultural chemical application systems. As a step towards the development of a field-scale sprinkler irrigation chemigation systems management model, a solute transport model that can simulate the time- and distance-evolution of the concentration of a nonreactive solute in an irrigation lateral is developed and evaluated in the study reported here. For modeling purpose, a lateral is conceptualized here as a hydraulic network consisting of a series of connected pipes, each delimited by outlet nodes. At the pipe-scale, solute transport is modeled as a one-dimensional advective process in which the applicable differential equation is solved with a quasi-Lagrangian integration scheme. Solutions to the transport problem, in a pair of consecutive pipes, are coupled through what is describe here as the nodal condition, which can be stated as: the concentration computed at the downstream-end node of a pipe constitutes the upstream boundary condition for the advective transport problem in the pipe just downstream. The model was evaluated in two phases. First, the soundness of the formulation and programmatic implementation of the numerical solution, to the pipe-scale advective transport problem, was tested through comparison of model outputs with analytical solutions. Evaluation of the predictive capacity of the lateral-wide model, in the context of a real-world application, was then conducted by comparing computed breakthrough curves of a nonreactive tracer with data measured along a pair of laterals. The results suggest that model performance is satisfactory.