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8-4 aeal-time Adjustments in Releases During actual real-time dispatching of releases, expected purchases and sales must be adjusted to reflect conditions of scheduled transmission line outages and critical transmission line loadings, and to ensure that specific transmission contract paths are being used. Western's dispatchers must be flexible to adapt to real-time power system needs and uncertain conditions, such as (a) economic market opportunities, (b) emergency deliveries, (c) transmission overloads or contractual schedule limits, (d) unscheduled customer deviations from power schedules, and (e) changes in forecasted reservoir operations, unit availability, and powerplant constraints. These conditions may make it economically beneficial to try to buy or sell more or less power than anticipated. Also, when adjacent utilities lose resources due to forced outages or maintenance requirements, they may seek emergency assistance from the Federal systems which was unanticipated. Transmission overloads or contractual schedule limits may restrict planned resource exchanges. Mid-month changes in water release volumes due to changes in forecasted runoff affects the water resources available. Such changes may require disposing of more or less hydropower energy. These all may alter the anticipated Federal energy available for load or marketing on a real-time basis and limit the capability of optimally using hydropower. Factors Which Affect Kaxt.wa a.leases Glen Canyon powerplant release constraints are key components of the Interim Flow restrictions. The absolute limits of 5,000 and 20,000 cfs have particular importance to aquatic and sediment resources. The extent of daily fluctuations affect all downstream resources. The frequency that releases exceed a certain flow are tied directly to the monthly release volume and peak energy demands. Historic operating practices under the constrains of Interim Flows have shown that peak releases do not reach 20,000 cfs unless the monthly release volume is at least 900,000 AF (daily average of 15,000 cfs). This is intuitive since the maximum allowable daily fluctuation of 8,000 cfs effectively limits the departure from the daily average. The uncertainties of power system load, purchase cost and availability, and transmission capability have historically tended to keep generation from strictly matching loads. Therefore, maxUnuffi releases are fairly predictable, largely a function of average daily release and allowable daily fluctuations. Variance from this equation largely results from the uncertainties cited earlier.