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.... ~. ong:3 27 Storage outflow relations for a 2 -percent chance of excess in outflow can be compared wi th those for the maximum observed flood volume developed in the previous section. The maximum observed data are shown as circles in figure 5. For the Delaware River the maximum observed requirements are somewhat greater than those for 2-percent chance. Similar comparisons are shown for 14 long-term gaging stations in figures described in the follow- ing section and indicate at these sites that the 2-percent chance storage re- quirements are not as great as would have been necessary to control some exceptionally great floods in the past such as that of 1951 in some areas. The method of developing storage-outflow curves for 2-percent chance of exceedance, was used to develop similar curves for 4-, 10-,20-, and 50- percent chance of exceedance in order to provide users with a wider selec- tion of design c ri teria. Storage-Outflow Frequency Curves Storage-outflow frequency curves (fig. 6-106) are presented in this sec- tion for 101 gaging stations operated for 10 or more years under unregulated conditions. The illustrations are in downstream order corresponding to the order of the stations in table 1. Each station is numbered in agreement with table 1, the map in figure 1, and with prior reports in this technical series. The curves in each illustration show the storage required to limit the outflow to the indicated rate with a chance of deficiency in storage or excess in out- flow ranging from 2 to 50 pe rcent. No allowance is made for evaporation or seepage losses. The upper limits shown on each figure represent the highest rate of discharge that would be reached for each probability if there were no reservoir storage. The storage-outflow frequency curves are developed from streamflow records extended to the base period 1921-60 except for 22 sta- tions in western Kansas which are extended to somewhat shorter periods. Gross outflow is in cubic feet per second per square mile and the correspond- ing storage requirement is depth in inches of runoff. Depth in inches is de- fined as the depth of an equivalent quantity of water spread over the entire basin above the site. Contributing drainage area is noted at the bottom of each figure and indicates that portion of the total basin containing a continu- ous drainage pattern that contributes to direct surface runoff. The circles and numerals appearing on the curves are identified by footnotes. Each set of curves is based on essentially unregulated flow. Other in- vestigators may wish to apply other criteria for identifying unregulated flow. For this report is was arbitrarily decided that all years of record at all sta- tions could be used in developing the outflow-storage relations except as fol- lows: (1) For station 9, (see table 1 for station names) the records used in filling out the base period were only those prior to closure of Lovewell Res- ervoir upstream. (2) Daily discharges for gaging stations 8, 14, 28, 50, 61, 70, 109, and 112 were adjusted for travel time and for daily inflow and out-