FLOOD01459

• County: Gunnison
• Community: Uncompahgre Valley
• Title: Upper Gunnison-Uncompahgre Basin Phase 1 Feasibility Study Summary Report
• Date: 5/1/1989
• Prepared For: Colorado Water Resources and Power Development Authority
• Prepared By: HDR Engineering, Inc.
• Floodplain - Doc Type: Project

6-4

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The three reservoirs modeled in Scenario 2B were able to el iminate
shortages to agricultural depletion demands that were identified in the No-
Action Alternative. Enhanced instream flow targets were met or exceeded
throughout the 32-year study period (1952-1983) on Ohio and Tomichi Creeks,
but not on upper Cochetopa and Paul ine Creeks, where insufficient physical
supply caused infrequent deficiencies. Tables 6.2 through 6.4 summarize the
monthly instream flows predicted by the model in specified locations on Ohio,
Tomichi, and Cochetopa Creeks with the three reservoirs in place.

The recreation potential of Castl eton and Sargents No. 3 reservoi rs
appear good. As shown on Figures 6.1 and 6.2, these reservoirs fill regularly
and are substantially full most of the time. Paul ine Reservoir, shown on
Figure 6.3, is often very low or near empty because of the lack of physical
supply. Blue Mesa Reservoir storage levels under this scenario differ from
the No-Action Alternative as depicted in Figure 6.4.

The Taylor Park Exchange Agreement stipulates that the UVWUAbe given a
credit to draw on Blue Mesa storage in direct proportion to Taylor Park
Reservoir releases made in excess of Gunnison Tunnel diversions, up to an
amount equal to their Taylor Park storage decree. Flows downstream of Taylor
Park Dam, Blue Mesa Reservoir inflows, and tunnel diversions were all
monitored in the model to keep track of credits and debits to the "exchange
account." As mentioned previously, the late season releases from the three
reservoirs increase late season inflows to Blue Mesa, which reduces the need
for Gunnison Tunnel diversions to draw on Blue Mesa storage during the latter
part of the growing season. This reduces the draw on UVWUA's storage credit
in Blue Mesa and results in the Taylor Park Exchange Account showing a higher
average storage credit than in the No-Action Alternative. The average
monthly exchange credi t under Scenari 0 2B is 5228 af /mo, compared to 4857
af/mo in the No-Action Alternative. This indicates that construction of the
three in-basi n reservoi rs increases the dependabil i ty of the UVWUA water
supply from Taylor Park Reservoir.