Grouped Response Units for Distributed Hydrologic Modeling

This paper introduces a method for distributed hydrologic modeling that eliminates the need for small computational areas while maintaining the requirement of computing runoff for homogenous watershed subareas. The model is designed from the ground up as a georeferenced model that can make maximum use of remotely sensed data such as rainfall from weather RADAR and land cover characteristics from LANDSAT or SPOT satellites. Other remotely sensed data such as snow‐cover extent and initial soil moisture can also be based on satellite data and be directly incorporated in the model. The method consists of grouping hydrologic response units that have similar response characteristics on the basis of classified land‐cover maps. Model parameters are unique to individual land‐cover classes. This reduces the need for model calibration and allows for the transfer of model parameters in both time and space. The model was applied to four watersheds in Southern Ontario. It was calibrated on the Grand River watershed and then applied to the three other watersheds without further calibration of the hydrologic parameters. Only the river roughness was adjusted.