Cold Regions Hydrology Workshop

Breakout Session Description and Status

Accurate Snow Water Equivalent Data Collection

The discussion led the group to identify five areas for improvement in the measurement of SWE:

1) WFOs need to establish NWSLI site IDs for data supplied by external users (including snow-water equivalent, snow depth, etc.). Also, locations of SWE data collected by outside observers as well as local networks established by WFOs should be consistent between observations and subsequent years. ACTION: This should be accomplished by the Service Hydrologist, Hydrology Focal Point, DAPM, or the responsible party for establishing the site IDs and maintaining local SWE networks.

2) Observers of snow-water equivalent data need to be reminded that using a 10:1 ratio of snow depth to water content is not an accurate, let alone reasonable assumption. ACTION: Regional personnel should remind MICs of this, who in turn should see to it this practice is no longer used.

3) WFOs can improve SWE data collection for River Forecast Centers by establishing 2 or 3 locations within a basin, and starting data collection in December or January. Discussion is ongoing between NCRFC and Central Region about the importance of early SWE data collection to support the January AHPS probabilistic forecasts. It is recommended each Region or River Forecast Center coordinate with the local office to begin data collection in January.

4) WFO can recruit new observers by putting a message on the WFO web-site, newspapers, post-offices, etc. New observers can be furnished with a 4-inch rain gauge, snow board, snow stake, and other pertinent equipment. ACTION: This should be accomplished by the WFO SH, HPM, DAPM, OPL, or other party responsible for establishing new cooperative observers.

5) There needs to be clarification on the measurement frequency of SWE data collected by WFOs, and the need to include snow depth (SD) with the 18Z snow-water equivalent (SW) observation. ACTION: National Headquarters should clarify to Regions, River Forecast Centers, and WFOs the new SCD requirements.

Based in part on some of these recommendations, NOHRSC has provided eleven snow measurement recommendations (pdf) on their NOHRSC Technology page under the NWS Policy and Snow Requirements section. NOHRSC also prepared a description of measurement errors and associated impacts (pdf) for sharing with data collectors and handlers. Action: Ensure a wide distribution of these recommendations within your offices and to your observers.