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<br />less than 10,000 <br />10,000-16,000 <br />16,000-31,500 <br />31,500-48,000 <br />over 48,000 <br /> <br />4 <br />7 <br />71 <br />13 <br />5 <br /> <br />data <br />under <br />preparation <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />this change, showing the dam releases beginning ap- <br />proximately one year before sta.rt of the GCES and <br />continuing through to near the end of the study. Op- <br />erational strategies, the physical and biological <br />environment, and recreational users were all adjusting <br />to this changing situation through.out the study period. <br /> <br />Flows during the study period varied considerably and <br />included flood flows, flows of less than 5,000 cfs, <br />nearly steady flows, and fluctuating flows. Table II-1 <br />shows the percent of days in specified flow ranges <br />during the study period and during- the filling period. <br />Low to medium flows were uncommon during the study <br />period. Most flows were at the h.igh end of powerplant <br />releases. Although 27 percent of the days during the <br />study had flows which fluctuated more than 10,000 cfs <br />during a 24-hour period, this generally occurred before <br />field work for most studies had begun, or was at times <br />which were not seasonally most important for the <br />critical resources. <br /> <br />Table II-1. Flow distribution during the GCES study <br />period and the Lake Powell filling period (in percent <br />of days). <br /> <br />study Period <br />(1983-1986) <br /> <br />Filling Period <br />(1963-1980) <br /> <br />Flow Range, in cfs <br /> <br />Fluctuations greater <br />than 10,000 cfs <br /> <br />27 <br /> <br />14 <br />