The CS performs the tasks needed to process historical hydrometeorological data and to estimate model parameters for a specific basin.
The models:

• simulate snow accumulation and ablation
• calculate runoff
• distribute runoff to the basin outlet
• channel route streamflow

The NWSRFS is a modular system that allows the hydrologist to select from a variety of models and to configure them in a manner that is descriptive of the basin.
All of the hydrologic models are available to the Calibration, Operational Forecast, and ESP systems.

As part of the calibration procedure, for a particular basin, the simulated streamflow is statistically and visually compared to the observed streamflow to determine the necessary model parameter adjustments.
The ideal model parameters are those with which the model simulated streamflow most closely matches the observed streamflow.