9676

• UCREFRP Catalog Number: 9676
• Author: U.S. Department of the Interior.
• Title: Preliminary Analysis
• USFW Year: 2001.
• USFW - Doc Type: Wayne N. Aspinall Unit Operations and the Draft Endangered Fish Flow Recommendations for the Gunnison and Colorado Rivers.
• Copyright Material: NO

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Upstream flooding due to ice jams above Blue Mesa would not be affected by any of the model runs
because the same criteria was used in all model runs to meet the winter target reservoir elevation that
reduces ice jams. If this criteria were changed to assist in meeting flow recommendations, ice flooding
could increase.

Compact Entitlement

The State of Colorado is entitled to waters from the Colorado River and its tributaries based on several
compacts, including the 1922 Colorado River Compact and the 1948 Upper Colorado River Basin
Compact. The State of Colorado estimates that at least 450,000 acre-feet of undeveloped water remains
of their Compact entitlement. As noted earlier, one of the purposes of the Aspinall Unit is to allow
Colorado to use its apportionment of water under the compacts. The Gunnison River, as one of the
largest tributaries to the Colorado River, is a strong potential source for this future water development.
Blue Mesa Reservoir holds one of the State of Colorado's largest uncommitted water supplies.

In general, model runs that reduce the frequency of filling Blue Mesa would reduce the potential for
Colorado to develop water supplies. In dry water years, operating to meet the flow recommendations
could result in Blue Mesa releasing up to 150,000 to 200,000 acre-feet of storage water more than the
Baseline Run. The effect of the flow recommendations on future Colorado water uses has not been
analyzed.

Relationship with the Black Canyon Reserved Water Right

The U.S. filed claims in 1971 for federal reserved water rights. In 1982, the Colorado Supreme Court
confirmed a decision by the Water Court granting the U.S. an unquantified federal reserved water right
for instream flows in the Gunnison River for purposes of the Black Canyon of the Gunnison National
Monument. In January 2001, the United States filed an application to quantify the reserved right.

The NPS conducted studies in the Black Canyon on vegetation, stream organisms, recreation access, and
stream morphology to provide data for quantifying the reserved right. Reclamation's policy has been to
support quantification of the reserved water right while continuing to meet Congressionally authorized
purposes of the Aspinall Unit. The NPS desired flows call for a year-round minimum flow of300 cfs and
depending on hydrologic conditions, a spring peak in excess of 12,000 cfs with specific ramping rates,
and inundation flows4 between 300 and 3,350 cfs. NPS desired flows are measured at USGS gage,
(Gunnison River below Gunnison Tunnel), at the upper end of the Black Canyon of the Gunnison
National Park.

Both the endangered fish and NPS desired flows call for a high spring peak. In attempting to meet the
fish flow recommendations at Whitewater, the fish flow model runs (Runs B, C, and D) indicate the
desired NPS peak would be met or exceeded in only 1 of the 26 model years. These model runs also
indicate at least 90 percent of the NPS desired peak flows would be met in 4 years, and 75 percent of the
peak would be met in 6 years. In the model, these occur in dry, moderately dry, or average dry years.

4Inundation flows provide an 85-dayminimum flows between May 1 st and July 31 st to
protect NPS resources.

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