Hydrology and Water-Quality Calibration and Validation of Minnesota River Watershed Model Applications

Hydrologic calibration is critical to parameter development for an HSPF model application, particularly for parameters that cannot be readily estimated by watershed characteristics. Calibrating hydrology is also necessary to form the basis for a sound water-quality calibration. Calibrating an HSPF model application is a cyclical process of making parameter changes, running the model, producing graphical and statistical comparisons of simulated and observed values, and interpreting the results. Observed data for hydrology and water-quality calibration include continuous stream flow (collected at gaging stations) for hydrology and ambient water quality samples obtained from reputable sources. Calibration is typically evaluated with visual and statistical performance criteria and a validation of model performance that is separate from the calibration effort. The methods and results for the hydrologic calibration and the water quality calibration are explained in the following sections.