Need for interaction

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The process of hydrologic forecasting requires human-machine interaction.
This is because:

• the equations, which represent the physics of the hydrologic cycle, do not perfectly model the actual movement of water
• the process we use to calibrate, or find specific parametric values for the models does not produce perfect results
• we do not perfectly observe rainfall or stream conditions as input to the models

In order to properly forecast a hydrologically connected series of sub-basins, a forecaster must make decisions for each location along the river where observed river conditions are available.
If values simulated by NWSRFS do not agree with observations, the forecaster must decide on the most likely error, and make adjustments.
When a river system is forecast with NWSRFS, a group of sub-basins are processed in a single batch run.
Errors in upstream sub-basins propagate into downstream basins, making forecasts for those basins less reliable.
The only way to avoid this problem is by making adjustments to reduce or remove the error in any sub-basin before processing downstream sub-basins.
The NWSRFS IFP provides the forecaster with this capability.

An additional benefit of the IFP is the enhanced display capabilities of high-resolution of color display terminals.