Distributed, physically-based models have been widely used for hydrological analysis; nevertheless, few models incorporate crop irrigation in the water balance. The Water Balance Simulation Model (WaSiM-ETH) includes modules for irrigation, evapotranspiration (ET) and water distribution, which allows its application in basins with irrigated land systems. Nevertheless, its applicability may be limited due to the data requirements to use the Penman-Monteith equation (P-M). In order to improve this disadvantage, the authors modified the WaSiM-ETH model by adding the "reference-crop" module that calculates the Potential Evapotranspiration (ETP) using a reference crop ET (ETref) and Crop Coefficients (Kc). The modified WaSiM-ETH model was used to simulate the hydrology of the Linares Irrigation System (SRL), in the Central Zone of Chile. The model was calibrated and validated, evaluating the correct operation of the "reference-crop" and irrigation modules. Results indicated that the modified WaSiM-ETH model allowed the incorporation of the crop's water consumption and the irrigation in the hydrologic simulation. In large watersheds the model worked correctly, while the model presented problems in small watersheds where the natural flow is smaller than the irrigation conveyed, due to the scarcity of information of volumes in channels and because the distribution of water does not follow exactly the water rights, a condition assumed for the modeling. The results allow concluding that it is possible to apply the modified WaSiM-ETH model in irrigated river basins, thus being a tool to simulate useful scenarios for decision-making.