BOARD00043 ‎(3)‎

• Board Meeting Date: 9/19/2006
• Description: CF Section - Finance Subcommittee Meeting
• Board Meetings - Doc Type: Meeting

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STATE OF COLORADO

Colorado Water Conservation Board

Department of Natural Resources
1313 Sherman Street, Room 721
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
www.cwcb.state.co.us

MEMORANDUM

Bill Owens
Governor

TO:
FROM:

Colorado Water Conservation Board - Finance Committee
Michelle Garrison, Water Supply Protection Program

Russell George
Executive Director

Rod Kuharich
CWCB Director

DATE:
RE:

August 30, 2006
Non-Reimbursable Investments
USGS Snowmelt Timing Study

Dan McA uliffe
Deputy Director

Introduction

Recent studies of streamflow timing in the Western United States indicate that over the past 50 years, snowmelt
runoff in much of the West is occurring earlier than in the past. The analysis noted that changes were most
pronounced in the Sierra Nevada, Cascades, and northern Rocky Mountains, and only minor changes in streamflow
timing were identified in Colorado. The study raised important issues about the potential effects of climate change
on water supplies in the west, but the results for Colorado were somewhat puzzling given local perceptions that
recently, melt has been occurring earlier in Colorado as well.

Because of the puzzling results for Colorado, the USGS Colorado Water Science Center conducted preliminary
analyses on a dozen SNOTEL and streamflow sites in selected river basins in Colorado. Results indicate that
snowmelt and runoff are occurring earlier at almost all of the sites that were tested, in some cases by as much as 2
weeks. There appear to be important regional variations in the snowmelt- and runoff-timing trends, with relatively
strong trends in the Animas and Arkansas river basins and weaker trends in the South Platte river basin. Changes in
snowmelt timing at the pilot study sites were strongly correlated with increasing springtime air temperatures. These
preliminary results suggest a more detailed analysis is warranted, which could provide new information having
important implications for water resource management and availability in Colorado.

Discussion

The USGS Colorado Water Science Center proposes a detailed analysis of snowpack melt timing, streamflow
runoff timing, and trends in monthly air temperature and precipitation in high-elevation areas in Colorado. The
objective is to document recent trends in snowmelt and runofftiming, and to quantify how those parameters are
affected by changing climate. Snowmelt timing will be analyzed for selected SNOTEL sites and streamflow timing
will be analyzed for selected headwater streams with minimal or no diversions. All of the major river basins in the
western part of the state, including those in the Front Range, will be covered. Climate data will be obtained from
meteorologic stations co-located with the SNOTEL sites, and trend analyses of monthly air temperature and
precipitation will be conducted. Results will be used to estimate potential changes in runoff amount and timing
under a variety of climate change scenarios to understand possible implications to water resources in Colorado
including changes in water use, reservoir operations, timing and magnitude of snowmelt flooding, drought
response, and availability of flow at certain times to meet instream flow rights.

Flood Protection. Water Supply Planning and Finance. Stream and Lake Protection
Water Supply Protection. Conservation and Drought Planning