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0015D3 23 Records analyzed are the months of record used in extending the data to the base period. All periods are shown for which records are equiva- lent to those at the site described in the location paragraph. Average base flow is the average annual base flow for the period of record. This is computed au the average of the yearly mean base flows, rather than the average of the mean monthly flows. Extremes are the maximum and minimum monthly mean base flow for the entire period of record. Remarks include descriptions of the extent of regulation and irrigation and other pertinent information. The base-flow data presentedin this part of the report are contained in three tables. The first table shows monthly and yearly mean base flow in cubic feet per second. Each monthly figure is the mean base flow for an entire month; no record is tabulated for a partial month. Likewise, each yearly figure is the mean base flow for a full year, and no figure is shown for a partial year. The me an of record summary at the bottom of the table is the mean monthly or yearly base flow as computed from the tabulated monthly or yearlymeans. The mean forthe base period is the me an month- ly or yearly base flow as computed from the tabulated monthly or yearly means plus the estimated monthly or yearly means (discussed subsequent- ly) needed to complete the base period. Because of the manner in which the extended data were estimated the mean yearly base flow will not agree exactly with the mean of the mean monthly base flows. The second table shows the mean monthly and yearly direct runoff for the base period. This is computed by subtracting the mean monthly and yearly base flow from the mean monthly and yearly total flow. Again, be- cause of the manner in which the extended data were estimated, the mean yearly direct runoff will not agree exactly with the mean of the mean month- ly direct runoff. The third table shows the monthly and yearly mean total flow. As in the first table, each monthly figure is the mean flow for the entire month and each yearly figure is for a full year. These values are from the water- supply papers of the U.S. Geological Surveyl2. The summaries at the bot- tom of the table are similar to the summaries in the first table. 12 U.S. Geological Survey, issued annually, Surface water supply of the United States; pt. 6b, Missouri River basin below Sioux City, Iowa and pt. 7, Lower Mississippi River basin: U.S. Geol. Survey Water-Supply Papers.