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ATTACHMENT B <br />(From Bowman and Carlson, 1994) <br />Table 2.�' Pulse^ ow recommendation for the central Platte River Valley ecosystem during May and <br />June. <br />Flow Duration Frequency (yrs) <br />Period (cfs) (dam) Exceedence ( %) <br />very wet May 1 - June 30* > 16,000 5 ** 1 in 5 (20 %) <br />wet May 1 - June 30* > 12,000 5 ** 1 in 2.5 (40 %) <br />normal May 20 - June 20 > 3,000 7 -30 * ** 3 in 4 (75 %) <br />dry May 11 - June 30 none * * ** all remaining (100 %) <br />* At least 50% of these pulse flows should occur during May 20 to June 20, with May 1 to June 30 as the <br />timeframe for broadset benefit for channel maintenance, and instream and wet meadow habitats. Occurrence <br />between February 1 and June 30 would accomplish the necessary effects for channel maintenance. The 10- <br />year running average for the mean annual pulse flow targets should range from approximately 8,300 cfs to <br />10,800 cfs. <br />** The duration of these pulse flows should emulate the historic, natural pattern: (a) ascended over <br />approximately 10 days, (b) cresting for approximately 5 days, and (c) descending over approximately 12 days. <br />* ** The target is for a 10 -year running average for the 30 -day exceedence flow (i.e., 10 -year running <br />average of the annual level exceeded for 30 consecutive days) of at least 3,400 cfs. A flow of 3,000 cfs <br />should be exceeded for 7 -30 days in at least 75% of years. Pulse flows should be followed by descending <br />flows approximating a rate of 800 cfs /day. <br />* * ** No pulse flows during May and June in driest years; target flows identified in the March 1994 <br />workshop (Bowman 1994), apply under dry year conditions. <br />16 <br />