18b ‎(2)‎

• Board Meeting Date: 11/18/2007
• Description: CF Section – Referred Non-Reimbursable Investments - Purgatoire River Water Conservancy District/CWCB Water Supply Protection Section - Purgatoire River Channel Capacity Improvements
• Board Meetings - Doc Type: Memo

STATE OF COLORADO
Colorado Water Conservation Board
Department of Natural Resources
1313 Sherman Street, Room 721
Denver, Colorado 80203
Phone: [phone]
Fax: [phone]
wuu . o~n cU. state. co.us
TO: Colorado Water Conservation Board
FROM: Steve Miller, Water Supply Protection Section
DATE: November 6, 2007
Bill Ritter, Jr.
Governor
H:uris D. Sherman
DNR Executive Director
Dan McAuliffe
Acting CWCB Director
RE: Agenda Item 18b. November 14-15, 2007 Board Meeting
Water Supply Planning and Finance Section Referred Non-Reimbursable
Investments -Purgatoire River Water Conservancy District/CWCB Water Supply
Protection Section Purgatoire River Channel Capacity Improvements
Introduction
Trinidad Dam, a feature of the Trinidad Project impounds the Purgatoire River upstream of the
City of Trinidad providing flood control and irrigation water to the city and lands below, as
well as recreation and fishery benefits at Trinidad Lake State park. The project was built by
the US Army Corps of Engineers in the 1970's. The US Bureau of Reclamation is responsible
for the irrigation components of the project which are managed and repaid by the Purgatoire
River Water Conservancy District ("PRWCD"). Pursuant to the Arkansas River Compact the
project is considered a post compact development, and may not materially deplete useable
Stateline flows beyond historical consumptive uses that occurred prior to 1949. Flood control
operations at Trinidad must therefore pass all flood inflows at the maximum possible rate
limited only by the safe channel capacity through Trinidad in order to not deprive downstream
rights, including John Martin Reservoir, an opportunity to utilize historical flood flows.
USBR, the Corps, Kansas, and the PRWCD are currently engaged in a Ten Year Review of
project operations including the issue of flood releases and safe channel capacity.
Discussion
Since construction of the dam the channel below the reservoir has deteriorated due to
vegetative encroachment, flow management, and land use changes. It is now believed that the
channel cannot carry the design flood release of 5,000 cfs, and it there is uncertainty as to
whether the currently designated release rate of 3,000 cfs can be safely carried. The Corps has
instructed dam operators to not exceed a 1,000 cfs rate until qualified observers can be on site.
This ratcheting down of the release rate is of concern to downstream water users, particularly
the State of Kansas, who benefit from high flood flows, but understand the life and property
Water Supply Protection • Flood Protection • Stream & Lake Protection • Rater Supply Planning & Finance
Water Conservation & Drought Planning • Intrastate Water Management & Development