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C0' ,', (l 0 \J ,_ LJ ,) 3. (c) 12 -month periods for users concerned with the minimum ex- pected inflow into large reservoirs, Low-flow frequency for 24- and 48-month periods and its application to stor- age studies will be covered in a later report. Low-flow frequency data extend and enlarge the opportunities for water- supply studies beyond the opportunities available from flow-duration data such as described in Technical Report No, 1. Low-flow frequency curves can be used to determine storage requirements, to select sites for water supplies, to appraise the adequacy of unregulated natural flow for allocation of water rights and dilution of wastes, and to delineate hydrologic character- istics. The need for low-flow frequency analyses for streams in Kansas has been long recognized, but the task of arranging the basic streamflow records for such analyses has been a major obstacle, With electronic computers the task has now been simplified, To prepare the data for electronic computers, more than 2,450 station years of daily discharges were transferred to punched tape, which totaled 25 miles in length, The tapes were passed through an electronic computer which prepared a list of the lowest mean discharge for six separate intervals of time ranging from 7 to 183 consecutive days for each year of record at each gaging station, These lists provided the nucle- us for the studies herein, The lists for each gaging station are maintained in the files of the U. S. Geological Survey in Topeka and are available to those who wish to make additional studies. This report provides water-use planners with low-flow frequency curves for Kansas streams, The curves could have been based solely on the period of operation of each gaging station, but this procedure would result in mis- leading data for small basins that had experienced a preponderance of either floods or droughts not typical of the long term experience in the general re- gion, The future expectance of flow needed for planning purposes would best be defined if records were available over a long-term period at all sites. Such a goal cannot be attained with the records now available, and the task of obtaining natural-flow records in the future will be complicated by man- made regulation, In the absence of long-term records at all sites, typical regional experience has been approached in this report by using correlation techniques to extend the experience of all records to a 37-year base period April 1920 to March 1957 and by applying to each stream the representative hydrologic experience of that region. As transfer of experience from one stream to another depends on cor- relation of unregulated flow, frequency curves should be developed now be- fore proposed artificial storage and land-use developments seriously modi- fy natural flow, Furthermore, curves for unregulated flow provide a base for future studies of the effect of regulation, diversion, and ground-water withdrawal.