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Six operational scenarios were identified for release patterns for a given annual release volume, that is, for how the <br />water is distributed on monthly, daily, and hourly bases. For reference, the release hydrographs for each scenario are shown <br />as the top panel (A) in figures 3 -8; the data sources are discussed in detail below. <br />1) Modified Low Fluctuating Flows (MLFF) — This is the current operational regime as selected in the 1995 <br />Environmental Impact Statement and record -of- decision for the operation of Glen Canyon Dam (U.S. Department <br />of the Interior, 1995) (fig. 3). <br />2) Steady Daily Flows (SDF) — This scenario eliminates fluctuations in releases that occur under MLFF on a daily <br />basis, but maintains the MLFF pattern of monthly volume releases (fig. 4). <br />3) Equal Monthly Volumes (EMV) — This scenario maintains the daily fluctuations of MLFF but replaces the pattern <br />of monthly volume releases with an equal volume for each month (fig. 5). ; <br />4) Steady Year Round (SYR) — This scenario eliminates both daily fluctuations and monthly volume changes resulting <br />in a single steady flow all year (fig. 6). <br />5) Seasonally Adjusted Steady (SAS) — This scenario eliminates daily fluctuations and revises the MLFF monthly <br />volumes to a pattern with the highest monthly volumes in May —June and lowest volumes in Aug —Dec (U.S. <br />Department of the Interior, 1995) (fig. 7). <br />6) Increased Daily Range and Down Ramp (IDR) — This scenario increases the MLFF daily ranges in discharge (up to <br />12,000 cubic feet per second [cfs] compared with 8,000 cfs) and down ramp rates (up to 4,000 cfs/hr compared with <br />1,500 cfs/hr) (fig. 8). <br />