DESCRIPTION AND EVALUATION OF PROGRAM USM

USM is a hydraulic-simulation computer program developed by the U.S. B ureau of Reclamation to analyze unsteady-flow conditions in canals. Th e program USM uses the method of characteristics to solve the complete Saint Venant equations for unsteady flow in open channels. This solut ion method yields accurate numerical results but sometimes requires mo re computer execution time than other methods. USM analyzes canal syst ems with a variety of structural boundary conditions, including check gates, weirs, siphons, and pumps. Check gates can have either manual o r automatic gate control. Branching canals, supercritical flow, and ch annel dewatering cannot be analyzed. This paper describes the model an d compares its strengths and weaknesses with those of other models. Se veral test data sets compiled by the ASCE Task Committee on Irrigation Canal System Hydraulic Modeling were used in the evaluation. USM simu lation results are compared to field data collected from the Central A rizona Project canal system.