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Table 9. Peak flows and mean monthly flows in the upper end of the 15- <br />mile reach during years in which peak flows at the State line gage were <br />about 22,000 cfs. Data from Appendix Tables I and II. <br />Mean monthly <br /> <br />Year Stateline <br />peak 15-mile <br />peak <br />April <br />May <br />June <br />1987 22,000 12,950 3,039 7,847 6,668 <br />1974 22,400 14,495 2,203 10,492 9,664 <br />1971 20,900 17,007 4,113 7,535 13,846 <br />1959 21,800 14,232 982 5,319 10,104 <br />1950 22,187 15,566 2,629 5,913 12,187 <br />1940 22,782 14,320 1,420 12,860 7,512 <br />Mean 22,012 14,762 2,398 8,328 9,997 <br />SD 641 -1,259 1,132 2,862 2,720 <br />Though we believe peak flows are important, they actually describe the <br />flows of only one day during the year. Obviously, one day of high water <br />would not be enough to maintain channels, flush introduced fish, prepare <br />the spawning substrate, prevent establishment of tamarisk seedlings, or <br />provide enough time for razorback suckers to spawn in flooded bottomlands. <br />In addition to these peak flows, recommendations for monthly flows during <br />April, May and June must be provided and would necessarily be something <br />less than that of the high day. To arrive at these, we employed the method <br />used above in arriving at peak flow recommendations, that is, to average <br />the mean monthly flows for those years used in the peak-flow recommenda- <br />tions. To obtain peak flows at the State line in the 30,000-40,000 cfs <br />range, we would expect mean monthly flows in the 15-mile reach of approxi- <br />mately 3,200-3,900 cfs in April, 10,800-12,900 cfs in May and 12,800- <br />16,200 cfs in June (Tables 7 and 8). Years that have provided the minimal- <br />ly acceptable peak flows of about 22,000 cfs at the State line, or an <br />average of 14,800 at the top of the 15-mile reach, have mean monthly flows <br />45