7886

• UCREFRP Catalog Number: 7886
• Author: Hydrosphere Resource Consultants.
• Title: Yampa River Basin Recommended Alternative, Detailed Feasibility Study
• USFW Year: 1995.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

I Reservoir Operating Studies
I Reservoir Operations
Three existing reservoirs are operated explicitly in the basin model--Stagecoach
Reservoir, Steamboat Lake, and Elkhead Reservoir. The operations of all other existing
reservoirs (most of which are located in headwaters areas) were assumed to have negligible
1 effect on basin hydrology either because of their small size or because of their mode of
operation.
Reservoir evaporation and storage carryover are automated in the model and storage and
release operations are driven by the relative priorities between reservoirs and demands. The
representation of releases from contract storage pools in the existing reservoirs was based on
information provided by the operators of those reservoirs. Generally speaking, users holding
existing contracts for storage water were the only demands allowed to have access to contract
storage pools. Release amounts were not adjusted for transit losses.
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Stagecoach Reservoir is modeled as having three storage pools: an industrial pool of
9,000 af, a municipal pool of 7,635 af, and a recreation pool of 16,640 af. These pool
allocations reflect implementation of the Yamcolo Exchange and anticipated reductions in the
Tri-State contract (it was learned near the end of the study that the Tri-State ownership totals
11,000 af; however the model scenarios reported herein were not re-run to reflect this new
information). In addition to water supply releases from the first two of these pools, Stagecoach
is also operated to generate hydropower and to maintain minimum instream flows below the
dam. Demands assumed to have access to the industrial pool are the Craig Station (after it has
exhausted its Elkhead supplies) and the Hayden Station (after it has exhausted its Steamboat
Lake supplies), although the Hayden Station does not presently have a formal Stagecoach
contract. Demands having access to the municipal pool are Steamboat Springs and Hayden, the
Mt. Werner Water and Sanitation District, the Steamboat ski area (for snowmaking), and small
industrial demands near Hayden. No water supply releases are made from the recreational
pool
.
As a result of the Four Counties decree at Stagecoach Reservoir, in most years total
decreed storage rights add up to greater than the physical capacity of the reservoir. Based on
discussions with the Division 6 Engineer, it was assumed that this "excess" decree capacity
would be administered as a refill right. This causes some complications in accounting between
the two contract pools (municipal and industrial) and the recreation pool. Because of the
additional decreed storage capacity over and above a single reservoir fill, there are instances
when contract pools could partially refill and could potentially deliver more than their contract
amount in a single year. While it is reasonable to expect this additional water to be stored
rather than bypassed, the "refill" water in the contract pools would likely be held in storage for
the next year. Therefore, the model limits deliveries out of the Stagecoach contract pools to
their contract amounts (e.g., industrial = 9,000 of per year) even though additional water may
actually be available in the pools as a result of refill.
Hydropower operations are implemented in the model by defining a set of decreasing
end-of-month storage targets in the winter. Hydropower releases are made only when the
reservoir is above this target after performing its other water supply release operations. The
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