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<br />flow recommendations were developed for each month using exceedance values of 75, 50,
<br />and 25 percent. The exceedance values were determined using daily values from the period
<br />1944 through 1964. The 25, 50, and 75 percent exceedance values are classified as flow
<br />recommendations for wet, average, and dry water years, respectively. The USFWS flow
<br />recommendations are shown in the table below with the USFWS flows calculated in ac-ft
<br />per month in the second table.
<br />
<br />
<br />Year Type Oct
<br />
<br />Nov
<br />
<br />Dec
<br />
<br />Jan
<br />
<br />Feb
<br />
<br />Mar
<br />
<br />Apr
<br />
<br />May Jun Jul
<br />
<br />Aug
<br />
<br />Sept
<br />
<br />Dry 109
<br />
<br />26S
<br />
<br />350
<br />
<br />345
<br />
<br />379
<br />
<br />3S2
<br />
<br />199
<br />
<br />334 621 40
<br />
<br />31
<br />
<br />47
<br />
<br />~verage 216
<br />
<br />374
<br />
<br />428
<br />
<br />410
<br />
<br />437
<br />
<br />471
<br />
<br />370
<br />
<br />906 1,600 209
<br />
<br />100
<br />
<br />10S
<br />
<br />Wet 331
<br />
<br />477
<br />
<br />499
<br />
<br />477
<br />
<br />493
<br />
<br />590
<br />
<br />603
<br />
<br />1,790 2,970 524
<br />
<br />285
<br />
<br />193
<br />
<br />
<br />Year Type Oct Nov Dee Jan Feb Mar Apr May Jun Jut Aug Sept Total
<br />
<br />Dry 6,690 15,741 21,483 21,176 21,012 21,606 11,821 20,501 36,887 2,455 1,903 2,792 184,067
<br />
<br />Average
<br />
<br />13,258 22,216 26,271 25,156 24,227 28,910 21,978 55,610 96,040 12,828 6,138 6,237 337,879
<br />
<br />We' 20,317 28,334 30,629 29,278 27,332 36.214 35,818 109,870 176,418 32,163 17,493 11,464 555,331
<br />
<br />The recommendations for channel scouring and maintenance flows were modified in the
<br />March 9, 1995 memorandum. The recommended channel scouring flows are 2,800 to
<br />3,000 CFS once every 4 years and recommended channel maintenance flows averaging
<br />1,500 to 1,800 CFS in the other 3 years, The January 23, 1995 letter stated that the lower
<br />value would be a target flow for an average water year and the higher value would be for
<br />an above-average water year. The duration for these modified flow recommendations is
<br />not specified in the March 9, 1995 memorandum. The January 23, 1995 letter recommends
<br />that the events be a minimum of 2 weeks.
<br />
<br />The current flow recommendations from the USFWS is their best attempt without ~ore
<br />specific biological, and other types, of data. Results from future studies were identified to
<br />be critical in determining and refining flow recommendation for the Duchesne River.
<br />
<br />SLC\ 1341 07\REPT1.DOC
<br />
<br />E.4
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