SPDSS_Task5_KeyStructure_NCWCD_CBT

• Title: SPDSS Task 5 - Key Structure, Northern Colorado Water Conservancy District and Colorado-Big Thompson Project
• Description: The Northern Colorado Water Conservancy District and Colorado-Big Thompson Project has been identified as a key structure for the South Platte Decision Support System ‎(SPDSS)‎ consumptive use and surface water modeling efforts. The purpose of this Task 5 memorandum is to document physical, legal, and operational aspects of those key structures identified.
• Decision Support - Doc Type: Task Memorandum
• Date: 7/7/2006
• DSS Category: Surface Water
• DSS: South Platte
• Basin: South Platte
• Contract/PO #: C153954
• Grant Type: Non-Reimbursable
• Bill Number: SB01-157, HB02-1152, SB03-110, HB04-1221, SB05-084, HB06-1313, SB07-122
• Prepared By: Leonard Rice Engineering

PHYSICAL INFORMATION
Constructed by Reclamation between 1938 and 1957, the C-BT Project consists of more than
100 structures, including 12 reservoirs, 35 miles of tunnels and 95 miles of canals (2/3 earth-
lined, 1/3 concrete-lined). Other features include dams, dikes, power plants, pumping plants,
pipelines, transmission lines, and substations.
The West Slope collection system is located in Division 5, Water District 51 within the upper
Colorado River basin. The key elements of the East Slope distribution system are located in
Division 1 Water Districts 3, 4, 5, and 6. Although descriptions of both systems are included
herein to provide a complete picture of C-BT Project operations, specifics regarding the eastern
slope collection and delivery system are the main focus of this memorandum due to their
location within the SPDSS study area. The layout of the system, connections between the
elements that make up the C-BT infrastructure, and associated background information are
discussed below in a generally upstream to downstream order.
West Slope Collection System
The C-BT Project's West Slope facilities collect high mountain runoff for diversion to the East
Slope, as shown in Figure 1. Water is stored in Lake Granby, Grand Lake, Shadow Mountain
Reservoir and Willow Creek Reservoir. The Willow Creek Pump Plant lifts the water 175 feet
from Willow Creek Reservoir where it flows via the Willow Creek Feeder Canal toward Lake
Granby.
The Farr Pump Plant lifts the water up to 186 feet from Lake Granby to the Granby Pump Canal,
where it flows 1.8 miles to Shadow Mountain Reservoir, through a connecting channel, and
ultimately to Grand Lake. Water also flows directly into Shadow Mountain Reservoir from the
North Fork of the Colorado River. On Grand Lake's southeast shore water enters the Adams
Tunnel on its way to the East Slope.
Green Mountain Reservoir (Structure ID 3603543)
Green Mountain Reservoir and Power Plant are located on the Blue River south of Kremmling.
Reclamation constructed Green Mountain Reservoir to maintain West Slope irrigation and power
generation during C-BT Project operations. Green Mountain Reservoir stores water to eventually
meet the requirements of water users' located downstream on the Colorado River, and to also
allow the C-BT to divert water to the East Slope during periods in which the C-BT Proj ect would
otherwise be out-of-priority. Green Mountain Reservoir has a drainage area of 559 square miles
and has a total capacity of 153,639 ac-ft covering 2,124 surface acres. The power plant has two
units with a total installed capacity of 26 megawatts. Green Mountain Reservoir's left abutment
spillway is controlled by three 25' x 22' radial gates and can discharge 25,000 cubic feet per
second (cfs).
Willow Creek Reservoir (Structure ID 5104620)
Completed in 1953, Willow Creek Reservoir captures snowmelt runoff in a 134-square mile
drainage area within the Willow Creek basin. The reservoir has a total storage capacity of 10,553
ac-ft covering 303 surface acres and typically operates with 3,329 ac-ft of active storage
capacity. The Willow Creek Pump Plant (ID 5100958) has a 400-cfs conveyance capacity and
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