Colorado River Ecology and Dam Management Proceedings of a Symposium May 24-25, 1990 Santa Fe, New Mexico (1991) / Chapter Skim
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Reservoir Operations
Reservoir Operations
Pages 207-225
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From page 207... ...
a reservoir hydrology model with monthly time steps and (2) a model of releases with hourly time steps to capture the hourly variation in value of hydropower and to characterize downstream flowsinput to a routing model or to other models for environmental parameters that are affected by diurnal flow and ramping rates.
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From page 208... ...
_ D o CL :~: Targets Time Flow Rate FIGURE 9-1 Relationship of hydrology and energy models. COLORADO RIVER ECOLOGY AND DAM MANAGEMENT Hydropower Model Compare Base Case to Other Minimum flows ~ I mpacts either historic data or output from a large multireservoir operation model, which is not shown.
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From page 209... ...
It therefore appears that the CRSS model underestimates evaporation by about 24%. As more data become available on reconciliation of theoretical versus actual mass balance of parameters in the reservoir and releases from GCD versus flows at Lee's Ferry, the way in which bank storage in Lake Powell is modeled should be improved.
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From page 210... ...
The determination of releases, for example in July versus May, is done in a simulation framework (same as the CRSS model) , which is to say that the monthly operating rule is assumed, not optimized as it would be by using a linear decision rule or a dynamic programming model.
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From page 211... ...
The current USBR approach to determining future releases is not an explicit one, such as would be obtained from a linear decision rule, but rather is a heuristic approach developed by considering both an optimistic and a pessimistic range of runoff from current snowpack and observing the resulting range of storage results. The procedure is then repeated monthly, and projected flows are updated by using actual current storage and revising future inflow estimates conditioned upon current snowpack conditions.
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From page 212... ...
U] 6 3 COLORADO RIVER ECOLOGY AND DAM MANAGEMENT _~ it, r \\ \ \ \ / \1 —'1 \ Initial \~ I Final ~ ~ ~ \.
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From page 213... ...
Hourly releases from upstream reservoirs are totally redundant for modeling GCD releases necessary to capture the impact of revised minimum instantaneous flow rates. Also, monthly release targets (the USER operation decisions)
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From page 214... ...
-/ '/ 0.0 i ~ ~1 1 1 1 1 1 i I 0 5000 10000 15000 20000 25000 30000 35000 40000 RELEASE (cfs) FIGURE 9-3 Glen Canyon Dam release probabilities during peak and off-peak hours (1978-1989~.
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From page 215... ...
. The data from which the base case was developed were monthly releases for the 23 years of operation of GCD, from which time-of-week excedance functions were developed.
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From page 216... ...
From reasons discussed above, an operator following a new random load and a higher minimum release will produce an average release
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From page 217... ...
Although the current 35% requirement is much greater than the minimum related flows, it is not necessarily greater than the average resulting from higher minimums, and periods when load is less than minimum generation could result if this contract requirement is not increased. OTHER RELATED WAPA REPORTS Report on Impact of Alternative Interim Flows WAPA has also produced a report related to the impact of possible increased minimum flows during the next 5 years (WAPA, 1989~.
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GCES ECONOMIC TEAM PROGRESS TO DATE The GCES II economic study team has completed an initial report (Bureau of Reclamation, 1990) on one important aspect of the way in which the impact of increased minimum flows should be analyzed—that is, what type of model is best for predicting the nature of the response to increased minimum flows by large utilities that are firm power customers of CRSP.
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From page 219... ...
ELFIN-an energy system simulation model developed by the Environmental Defense fund; (2) EGEAS-an investment timing optimization model used by the Electrical Power Research Institute; and (3)
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From page 220... ...
The research releases requested by GCES, however, specifically require both high and low ramping rates. It was necessary for WAPA to define the terms high and low before the cost of these flows could be modeled in the 1990 report on cost of research flows.
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Oct Nov Dec Jan Feb Mar Apr May Jun o -l ..
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From page 222... ...
Figure 9-8 shows actual dam releases, the average releases for peak and off-peak hours, and an assumed load. The hypothetical load must always be greater than the 35% of firm capacity (about 10,700 cfs)
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The hourly data for all 23 years of operation of GCD were used to develop the following summary of historic ramping rates. The average maximum ramping rates in delta cfs/hour for durations of 1-7 hours are shown in Figure 9-9 for each of the 7 days of the week.
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From page 224... ...
The GCES II economic impact research team, which is charged with analyzing the economic cost of possible increased minimum releases from Glen Canyon Dam, should use hourly historic data for developing both the generation and load probability distributions. This apporach will improve the modeled shapes of both the load pattern and the dam release pattern relative to those used in the WAPA reports to date.
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From page 225... ...
Analysis of Altemative Release Rates at Glen Canyon Dam. Westem Area Power Administration, Salt Lake City Area.
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