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• Board Meeting Date: 5/20/2008
• Description: CWCB Director's Report
• Board Meetings - Doc Type: Memo

and provides several new products that include: modeled snowpack
characteristics such as snow ripeness, melt rates, mean snowpack
temperature, and sublimation losses in a variety of alphanumeric, gridded,
map, and time-series representations. SNODAS products and data sets are
available in near real-time to end-users from the NOHRSC web site and
FTP through the National Snow & Ice Data Center (NSIDC;
http://nsidc.org).
COLORADO SNODAS OVERVIEW
The CWCB goal in this project has been to test SNODAS model output to
determine how useful it might be for water management at the state and
local level and provide reports and documentation of findings to the model
developers and snowpack and streamflow forecasters. The initial phase
was to provide SNODAS model output specifically for Colorado and
develop the calculations of the gridded data set. Phase II and III have
Riverside Technology, inc.. of Fort Collins analyzing and comparing
SNODAS calculations to other data sets, developing water balance budgets
for a few key points, and then coupling the SNODAS data with an NOAA
experimental distributed hydrologic model to draw comparisons to
Colorado River Basin Forecast Center simulations.
DAILY MAPPING OF SNODAS OUTPUT- PHASE I
The "Enhanced Snowpack Assessment Project" or "SNODAS
project" are the same and are terms that are used interchangeably in
Colorado. The project is an adaptation for Colorado of the nationwide
Snow Data Assimilation System's (SNODAS) modeled snowpack. The
goal is to provide quantitative information for flood preparedness and
water management objectives like reservoir operations and stream flow
forecasts. The operational SNODAS model is being used to calculate
basin-average SWE values for the USGS eight-digit Hydrologic Unit Code
basins. These averages are then aggregated back up to Colorado's large
watersheds and shown in the legend in the upper right.
Reclamation has graphical and alphanumeric products from
SNODAS for Colorado on their precipitation products website found at
httpa/www.usbr.gov/pmts/rivers/awards/Co/Colorado.html.
The SNODAS modeling products are relatively new. The project
has provided maps since data became available in November 2003.
Reclamation maintains a webpage of SNODAS output and an archive of
daily maps, two-week animations, and yearly animations for the following
parameters and their basin averages:
• Snowpack SWE
snowpack depth
snowpack SWE one-week change
24-hour snowmelt
• 24-hour snowpack temperature.
This project phase was replicated in the State of Washington and their data is house on this website as well.
RESULTS PHASE I
Comparison of SNODAS SWE with areas close to the NRCS Snow Telemetry (SNOTEL) sites has
shown that the model is performing reasonably. SNODAS has the potential to improve snowpack assessment
because the data are more numerous and spatially continuous. An example calculation of the utility of the 1 km
grid is that SNODAS provides approximately 4,000 data points for SWE in the Upper Rio Grande basin, instead
of a few SNOTEL data points.
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