WMOD00425

• Title: Demonstration of Improved Operational Water Resources Management Through Use of Better Snow Water Equivalent Information
• Date: 9/1/2002
• Weather Modification - Doc Type: Report

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the applied research and development of such an SAA and did so in the succeeding 3 years. The
results were published in Super and Holroyd (1998).

1.3 GCIP Applications of the SAA

In 1997, Reclamation submitted a proposal to the GCIP. The proposal, No. GC97-0045, was
selected for funding by NOAA's OGP, and work began in 1998. The principal goal ofthe
proposal, entitled "Demonstration of Improved Operational Water Resources Management
Through Utilization of Better Snow Water Equivalent Information," was to significantly improve
estimation of SWE distributions and snow cover. This was to be accomplished by the SAA's
provision of SWE estimates to the NWS's National Operational Hydrologic Remote Sensing
Center (NOHRSC), which would use them in their snowpack models and direct the results to the
operational river models at the MBRFC. These river models, which provide crucial streamflow
forecasts to Reclamation, would thus be improved by more accurate snowpack inputs.

1.4 Snowpack Estimation and Hydrologic Modeling

NOHRSC is the NWS center of expertise in satellite and airborne remote sensing and geographic
information systems (GIS) used to support the NWS operational hydrology program for the
United States. The most widely used NOHRSC products estimate snow cover properties with
data collected by airborne, satellite, and ground-based sensors. The center operates two
terrestrial gamma radiation detection systems on low-flying aircraft to infer snow water
equivalent over a network of more than 1,900 flight lines covering portions of 27 States and
7 Canadian provinces. NOHRSC developed the Snow Estimation and Updating System (SEUS),
which uses a geographic information system to store, analyze, and display the spatial data
necessary to perform the estimation. Reclamation originally intended for SAA SWE estimates to
be ingested in SEUS, but NOHRSC later decided to replace it with a more sophisticated system
called the Snow Data Assimilation System (SNODAS). This system is currently being
implemented on a test basis. SEUS never had the ability to assimilate SWE observations from
radar, as does SNODAS.

The NWS River Forecast System (NWSRFS) (Burnash, 1995) consists of various components,
including the Operational Forecast System (OFS). Within the OFS is the SNOW-17 model,
which calculates snow accumulation and ablation (sublimation and melting). This model passes
rain plus snowmelt to a bulk hydrologic runoff model called the Sacramento Soil Moisture
Accounting (SAC-SMA) model. Neither model now has input from SNODAS, but this will
change once the latter becomes operational. Reclamation has recently completed work to input
SAA SWE estimates to SNODAS.

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