17a ‎(2)‎

• Board Meeting Date: 11/17/2007
• Description: CF Section – Bundled Non-Reimbursable Investments - High Resolution Gridded Sublimation Estimates
• Board Meetings - Doc Type: Memo

STATE OF COLORADO
Colorado Water Conservation Board
Department of Natural Resources
1313 Sherman Street, Room 721
Denser, Colorado 80203
Phone: [phone]
Fax: [phone]
wuu*. c~scb. state. co. us
Bill Ritter, Jr.
Goc error
TO: Colorado Water Conservation Board Members
Harris D. Sherman
DNR Executise Director
FROM: Michelle Garrison, Water Supply Protection Program
Joe Busto, Flood Protection & Dan McAnhffe
Acting CWCB Director
Weather Modification Permitting Program
DATE: November 1, 2007
SUBJECT: Agenda Item 17a, November 14-15, 2007 Board Meeting
"Bundled" Non-Reimbursable Investments
High-Resolution Gridded Sublimation Estimates
Introduction
Sublimation is a process that removes moisture from the snowpack. In seasonally-snow covered
catchments, sublimation can have a large effect on water supply, particularly in years of drought.
In recent years, such as 2004, runoff has been significantly lower than expected based on near-
normal snowpacks. The Spring of 2004 was warm and windy, conditions that favor high rates of
sublimation. Sublimation can be calculated using meteorological data, but stations are sparse in
the mountains, particularly at high elevation. Spatial variability in sublimation may be large due
to the complex terrain and associated wind patterns in mountainous terrain. Extrapolation of
sublimation estimates from the sparse data collection network is highly uncertain. Water-supply
forecast models commonly use estimates of sublimation rather than actual data, leading to
uncertainty in water-supply forecasts.
Discussion
The USGS Colorado Water Science Center proposes to develop and test a relatively low-cost
network of instruments for measuring sublimation in a pair of mountain basins in the northern
Front Range of Colorado. One basin will be in the upper Colorado watershed on the west side of
the Continental Divide, and the other basin will be in the headwaters of the South Platte
watershed. Both of these basins have existing or planned research-quality meteorological stations
operated by the USGS that can serve as an instrumentation backbone. Additional, lower cost
instruments will be installed at 4 to 6 sites in each study basin to provide increased spatial
coverage.
The purpose of the study is to provide high-resolution estimates of sublimation based on actual
data. One objective is to determine the minimum data requirements and instrumentation for
Water Supply Protection • Flood Protection • Stream & Lake Protection • Rater Supply Planning & Finance
Water Conservation & Drought Planning • Intrastate Water Management & Development