The isotope profiling snow gage: twenty years of experience

The gamma transmission profiling snow gage has been in use for about two decades. Sufficient experience has now been gained to evaluate its general utility in snow hydrology research and operational forecasting. The gage produces an incremental depth-density profile with minimal disturbance of the snowpack. Its principal value lies in its ability to repeatedly measure the same vertical section of snow and thus record density changes through time. The snow gage has been an essental part of many studies in the mid-elevation snowpacks of the Sierra Nevada. Data obtained with the instrument have been subject to errors resulting from source decay, electronic variations, and physical influences of the access tubes on the measured snowpack. Overall complexity and expense of the snow gage limit its use in routine monitoring and forecasting applications. The profiling snow gage continues to have great potential in various snowpack investigations.