In hydraulic modeling is important to identify the advantages and disadvantages of a mathematical model. The aim of the present paper consists in to report the results of an exercise of application realized to establish the one-dimensional HECRAS model efficiency in simulating hydraulic behavior of a river with high flow branches and diversions, considering the Magdalena River near Canal del Dique. Based on field data collected in June 2005 (discharge and transversal sections measurements) and hydraulic information of discharges and levels in two gauging stations (Calamar in the Magdalena River and INCORA K7 in the Dique Channel). The model calibration was performed, subsequently, a validation processes was developed using an entrance hydrograph between 1st June 2004 and 1st November 2005, and comparing with the registered hydrograph in the INCORA k7 station located close to the Dique Channel entrance. The results prove the model efficiency and his high predictive capability in that conditions.