The computer program HEC-RAS can be used to model irrigation canal systems to evaluate canal hydraulics for both steady and unsteady flow conditions. An example application is presented to illustrate how the program can be used to analyze canals with inline structures, inverted siphons, pumping plants, and turnouts. A very useful feature of the program is the ability to illustrate results graphically. For design applications alternative designs can be readily evaluated by using the program option for comparing various combinations of geometry and discharges. RAS permits the use of complex cross section shapes for both open and closed conduit sections. GIS-based maps and aerial photographs can be included with the channel geometry to present realistic depictions of canal alignments, and photographs of structures can be included with geometric data to provide visual references to these features. For unsteady flow analyses the program provides a straightforward and stable solution procedure to evaluate transient flow conditions in canals. An example of unsteady analysis described in this paper is the calculation of surge waves resulting from a pumping plant flow rejection.