BOARD01460

• Board Meeting Date: 5/19/2003
• Description: Flood Section - Reporting on Weather Modification for Colorado and the Western USA
• Board Meetings - Doc Type: Memo

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STATE OF COLORADO

Colorado Water Conservation Board

Department of N atoral Resources
1313 Sherman Street, Room 72 I
Denver, Colorado 80203
Phone: (303) 866,3441
FAX: (303) 866,4474
www.cwcb.state.co.us

MEMORANDUM

Bill Owens
Governor

TO:

Colorado Water Conservation Board Members

Greg E, Walcher
Executive Director

FROM:

Larry Lang, Chief, Flood Protection Program
Joe Busto, Flood Protection Program

Rod Kuharich
CWCB Director

DATE:

Dan McAuliffe
Deputy Director

May 1, 2003

SUBJECT: Agenda Item 23.e - May 6, 2003 CWCB Meeting
Reporting on Weather Modification for Colorado and the Western USA

Introduction
The State of Colorado has had a weather modification program since 1972. The program is designed
to assure programs are monitored for public safety and the environment and that the operators are
qualified and efforts are coordinated with the State of Colorado. In 2002 the active permits doubled
from three to six for wintertime ground based precipitation enhancement programs. Approximately
25% of Colorado's snow fields are now in a target areas for cloud seeding programs. There are 65 new
generators in the central Rocky Mountains, 20 in the San Juan Mountains, and 20 in Gunnison County.

The principle wintertime cloud seeding operator in Colorado is Larry Hjermstad of W estern Weather
Consultants, Inc. out of Durango. In March 2001 Mr. Hjermstad release a report entitled "An Analysis
of Regional Snotel and Ski Area Precipitation Data to Evaluate Precipitation Changes Resulting from
Ten Seasons of Wintertime Cloud Seeding Operations over the Vail Ski Area". Conclusions from this
study showed for Snotel data there was a 15.6% average increase in the observed precipitation at the
Vail Ski area compared to what was likely to have occurred. What also was developed was a better
understanding of the percentages of increase for each directional approach of storms. This study has
contributed to the increase interest by water users.

Existing wintertime permits in 2002 were for Grand Mesa, Vail/Beaver Creek, Western San Juan
Mountains and Telluride/San Miguel Drainage. In 2002 in response to water deficits from the drought
new programs were created for the Central Rockies (Denver Water and Upper Arkansas WCD, Eastern
San Juan Mountains (Southwestern Colorado WCD, San Juan WCD), Gunnison County (Gunnison
County, Crested Butte, agricultural users, etc.) and a permit was renewed for Telluride/San Miguel
Basin (Town of Telluride, San Juan WCD, Southwestern Colorado WCD).

Final reports from the wintertime operators are due next month and a presentation by Larry Hjermstad
of Western Weather Consultants, Inc. and Don Griffith of North American Weather Consultants, Inc.

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