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

points in a basin, and not just at forecast points. A study should be performed to determine if the SNODAS-
RDHM system could provide reliable information at internal points in a basin.
In the next phase, improvements in snowpack assessment could be achieved by integrating the SNODAS system
with forecasting models at CBRFC. CBRFC is in the process of implementing RDHM for the Colorado River.
Recent development of historical datasets to drive RDHM allows the models to be calibrated and provides a
basis to develop procedures for updating model snow-water-equivalent. Gridded estimates of snow-water-
equivalent from CBRFC could be coupled with SNODAS snow-water-equivalent to produce improved volume
and spatial estimates of Colorado snowpack. Combining these two estimates will result in improved SNODAS
products from NOHRSC and more accurate streamflow forecasts from CBRFC.
PHASE III INTERGRATING SNODAS DATA TO FORECAST MODELS
In Phase II, RTi investigated using SNODAS data to drive a distributed runoff model. Quantitative use of SNODAS
data for snowpack assessment was constrained by a limited period of data availability and volume biases in
precipitation inputs to SNODAS. RTi proposes to integrate the SNODAS data with forecasting models at the
Colorado Basin River Forecasting Center to address limitations identified in Phase II. RTi plans to use the SWE grids
from SNODAS in conjunction with SWE estimates from the CBRFC to generate updated grids that represent the best
estimate of snow volume and spatial distribution in selected Colorado basins. Integrating the SWE estimates from
SNODAS and CBRFC will result in improved SNODAS products from NOHRSC and more accurate streamflow
forecasts. Phase III will also focus on automating snow data processing and display for the State of Colorado. Tools
will be developed to process SNODAS and SNOTEL data into maps that can be disseminated to the public. RTi will
deliver historical snow data to provide context for current snow conditions.
PROJECT OBSTACLES
This is a relatively new data source with no historical averages or long data sets to work with. It is a complicated
product that will require much analysis to tailor, refine, and develop products that are useful. That being said the daily
mapping products are online and water managers can utilize what we have developed so far to track the melt out of
snowpack and resulting streamflow. In order to truly use SNODAS operationally and quantitatively water balance
budgets and model fixes or correction factors may be warranted for each basin.
CONCLUSIONS
It is cautioned that the Enhanced Snowpack Assessment Project uses experimental data and should be used
provisionally in these early years. Improvements to the model will be made over time and confidence in the output
will continue to increase. Water managers have recognized the potential of this project and expressed their support
with statements such as: "Could improve the ability to estimate SWE above any particular point such as a reservoir or
flood-prone area"; "more detailed than what is currently available"; and "should improve forecasts". There are
unprecedented demands on our water resources and it is imperative that we modernize and be able to quantitatively
assess the water year and plan accordingly. It is our hope that investment in new technologies and systems like
SNODAS will assist us in developing greater certainty in our assessments of SWE, streamflow prediction, and
resultant water management decisions.
ACKNOWLEDGEMENTS
The project is designed to complement Colorado's NRCS Snow Survey's products and not replace them.
Indeed, SNOTEL provides critical data to SNODAS. We would like to acknowledge and thank the Colorado NRCS
staff members Mike Gillespie, Chris Pacheco, and Thomas Pagano for their assistance in sharing data and insight for
the development of the mapping and calculations for this project and commenting on reports. We also would like to
the U.S. Bureau of Reclamation, the NWS Office of Hydrologic Development, and Colorado Basin River Forecast
Center. Jay Day and his scientific team of Amy Volckens and Michael Thiemann at RTi are commended for their
commitment to analyzing and using SNODAS to assist the CWCB with the adaptation of SNODAS for water
management objectives. This is amulti-agency collaboration built on the best science available, but is in need of
continual change and refinement. Feedback on this applied research project is welcomed and can be directed to the
CWCB at joe.busto(a~state.co.us [phone], Michelle Garrison at michelle. arrg ison(ae,state.co.us [phone].
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