BOARD02469

• Board Meeting Date: 7/18/2005
• Description: CWCB Director's Report
• Board Meetings - Doc Type: Memo

For the purposes of completion of various programmatic requirements and in response to
the snowmelt flood threat, staff completed a number of visits to communities around the
state to discuss the flood threat situation and to assist the local communities in preparing
for potential high runoff.

In addition, the Flood Protection Section is active on an on-going basis to place online
information onto the CWCB website. A number of new items were developed on the
web this year in addition to the standard array of available data and important links.

Please view the Flood Section's website link at http://cwcb.state.co.us/Flood 1ntIo.btm
for additional information regarding online service.

Starting in mid-March 2005, staff monitored snowpack in Colorado watersheds, as
measured by inches of Snow-Water Equivalent (SWE) and % of 30-year average of
SWE. SWE is measured daily at the NRCS automated SNOTEL sites, and reports are
posted on the Internet. The inches of SWE measured at the SNOTELs represent the total
amount of water equivalent stored as snow in the portion of a particular watershed
represented geographically by each SNOTEL. The % of average SWE represents the
amount of water stored as snow in the portion of a watershed represented by each
SNOTEL as compared to a 30-vear average amount for that watershed. Both the absolute
number (inches ofSWE) and the relative number (% of average) are needed to paint a
comprehensive picture of conditions in the state's watersheds.

Staff monitored these numbers on a frequency ranging from every four or five days to
every day, depending on weather conditions in the mountains. Approximately once a
week the SWE numbers were assembled into tables and incorporated into the Weekly
Snowmelt Flood Updates.

Clearly three basins (Gunnison River, Upper Rio Grande, and San
MigueIlDolores/Animas/San Juan Rivers) had a very high proportion of SNOTELs
reporting high relative numbers. Another measure of regional snowmelt risk is basinwide
SWE as a percentage of 30-year average. The list below summarizes that percentage of
average (May 12,2005 values below are used for demonstration purposes) for all 8 major
river basins in Colorado:

. Gunnison River 150%
. Upper Colorado River 102%
. South Platte River 100%
. Laramie and North Platte Rivers 90%
. Yampa and White Rivers 81%
. Arkansas River 128%
. Upper Rio Grande 176%
. San MigueIlDolores/Animas/San Juan Rivers 155%

In addition to the table above, a graphical representation of the May 5, 2005 snowpack is
shown below for illustration purposes.

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