Snow course data is used in calibration of snow accumulation and melt. Model calibration can seem esoteric, until you have experience doing it. It is best, however, to do calibration systematically. See the Hydrologic Journal for calibration methods for land surface and snow parameters. It is certainly prudent to find out if a hydrologic method that you are considering is applicable in your region or watershed, and if the calibration of the method has demonstrated acceptable accuracies.
Many watersheds are ungaged.
Hydrologic models can be applied to ungaged streams when model parameters represent the physical characteristics of the streams. Calibration to nearby gaged watersheds is the verification that your hydrologic analysis is consistent with field data. In the U.S. check the USGS and NOAA web sites. More historic and real-time data is becoming available every month on Internet. Data is also available on CD-ROM's from Hydrosphere Data Products and EarthInfo .