Field-Scale Sprinkler Irrigation System Hydraulic Model. I: Hydraulic Characterization

Abstract

A mathematical model for a field-scale hydraulic characterization and simulation of solid set sprinkler systems with single-line and double-line lateral layout configurations is developed. This paper describes the hydraulic equations, numerical solution algorithms, and the hydraulic characterization functionality of the model for a system with single-line laterals. Numerical solutions of the lateral and mainline hydraulic equations are based on standard manifold hydraulics. A rigorous and flexible formulation of the sprinkler hydraulic problem is obtained by coupling the energy equation for each lateral and mainline segment with the continuity equation at a node. The resulting set of equations is then solved iteratively, starting from the distal end sprinkler or mainline outlet and moving sequentially upstream. The hydraulic characteristics of the sprinklers is defined based on manufacture’s pressure head and discharge data, and the hydraulic characteristics of each mainline outlet are computed by the system hydraulic characterization functionality of the model. The cubic spline method is used to interpolate mainline outlet discharges from the respective hydraulic characteristics curves as a function of total heads, effectively providing the interface for coupling the numerical solutions of the laterals and the mainline hydraulic equations. Evaluation of the hydraulic model with field data suggests that the hydraulic model is accurate. A companion paper describes the formulation of the hydraulic equations and numerical solutions for sprinkler systems with double-line laterals and the system simulation functionality of the model.