Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2015
Publication Date: 1/18/2016
Publication URL: https://handle.nal.usda.gov/10113/5801857
Citation: Bautista, E., Schlegel, J.L., Clemmens, A.J. 2016. The SRFR 5 modeling system for surface irrigation. Journal of Irrigation and Drainage Engineering. 142(1):1-11.
Interpretive Summary: SRFR is a modeling system for surface irrigation and a central component of WinSRFR, a software package for the analysis of surface irrigation systems. SRFR predicts the coupled surface and subsurface flow of water in a surface irrigation system as a function of system type, geometry, hydraulic resistance and infiltration characteristics of the soil, and the rate of water inflow as a function of time. SRFR evolved from research models that were first developed in the 1970's, and thus based on software architectural concepts that are now obsolete. Since upgrades to the software were becoming increasingly difficult to implement, SRFR was reprogrammed using a modern object-oriented architecture. This article provides an overview of the governing equations, computational methods, and software architecture of the new modeling system, SRFR 5. The upgraded software is less prone to experiencing computational incidents than previous versions, partly as a result of improved algorithms, but also as a result of improved management of computations and a modern structure for handling failed computations. The new software makes extensive use of software components known as classes and subclasses. Those components have already facilitated the modification of existing modeling capabilities and the addition of new ones. SRFR 5 exposes its functionality through an application programming interface, which is accessible to third party developers, and is better suited to support the continued development of the WinSRFR software package. This information should be of interest to engineers, researchers, and software developers interested unsteady open channel flow modeling.
Technical Abstract: The SRFR program is a modeling system for surface irrigation. It is a central component of WinSRFR, a software package for the hydraulic analysis of surface irrigation systems. SRFR solves simplified versions of the equations of unsteady open channel flow coupled to a user selected infiltration model. SRFR was reprogrammed using a modern object-oriented architecture with the objective of facilitating its continued development and, thus, the addition of new modeling options and functionalities. The upgraded software is SRFR 5. An important component of the modeling system is the code that manages computational incidents. While the computational methods used by SRFR 5 have been widely tested and are generally robust, calculations are prone to failures due to failures of the algorithms used to solve the non-linear finite difference system of equations, discretization problems, and problems with the determination of the appropriate boundary condition at each computational time step. Code that manages computational incidents has been greatly enhanced in SRFR 5. SRFR 5 has undergone systematic testing, partly to fix programming errors, but also to improve computations leading to unacceptable volume balance errors. This article discusses the SRFR 5 modeling system, and provides details about its computational methods, architecture, and new features.