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. OSli.~ Table 1. Summary of river reaches, streamflow-gaging stations I river distances, drainage areas, and analysis periods used at selected surface-water sites along the iower Purgatoire River, [NN. no numbers; n, no data; NO, no da~ were used] Site U.S. Geological Dlatance Analysis number Survey Station downstream Dralnaga period of (see station name1 from area station Trinidad Dam (aquare miles) record2 fig. 1) number (river miles) (yeara) Reacltl NN NN Trinidad Dam (upstream study boundatY) 0 Q1 07124410 Purgatoire River below Trinidad Reser;voir 0.1 672 1984-92 Q1A 07124500 Purgatoire River at Trinidad 1.3 795 1957-67 Q1B 07125000 Purgatoire River near Hoehne 12.1 857 1957-67 . TJ 07125100 Frijole Creek near Alfalfa 80 1957-67 12 07125500 San Francisco Creek near Alfalfa 160 1957-67 . QIC 07126000 Purgatoire River near Alfalfa 35.5 1,306 1957-67 ReacloZ Q2 07126300 Purgatoire River near Thatcher 60.6 1,791 1984-92 T3 07126325 Taylor Arroyo below Rock Crossing near Thatcher 48.4 1984-92 T4 07126390 . Lockwood Canyon Creek near Thatcher 41.4 1984-92 T5 07126415 Red Rock Canyon Creek at mouth, ne~ Thatcher 48.8 1984-92 T6 07126470 Chacuaco Creek at mouth, near Timpas 424 1984-92 T7 07126480 Bent Canyon Creek at mouth, near Timpas 56.2 1984-92 ReaCh 3 Q3 07126485 Purgatoire River at Rock Crossing neaf Timpas 100.7 2,635 1984-92 Q3A 07126500 Purgatoire River at Ninemile Dam ne'V Higbee 113.5 2,752 ND Q4 07128500 Purgatoire River near Las Animas 159.2 3,318 1984-92 (downstream study boundary) NN NN Purgatoire River at mouth 162.5 lStation names may be different from the stream names shown in figure, 1. 2Length of available streamflow record used for daily traveltime and g~n-and~loss analyses; streamflow records may exist for other time periods. is a useful visual tool for examining the central tendency and for summarizing the distribution of selected streamflow data. When plotted on the same scale, boxplots can be compared visually, and differences and similarities among surface-water sites or between different seasons can be identified. The median (50th percentile) is the center value of the data distribution and is shown as a solid line splitting the box, which indicates that 50 percent of the data are less than or equal to that reported value. The quartile skew of the data distribution is seen by comparing the parts of the box above and below the median line. For a linear scale, if the upper part is larger than the lower part, the data are skewed to the high values, The interquartile range represents the middle 50 percent of the data (variation or spread of the data) and is the enclosed part of the box between the 25th and !75th percentiles. The lengths of the vertical lines i( whiskers) compared to the length of the box indicate how stretched the tails of the data distribution are. The whiskers extend to the last observation that is .within 1.5 times the length of the box (1.5 times the ,interquartile range). Standard boxplots (Helsel and !Hirsch, 1992) provide concise visual summaries of the I !presence or absence of unusual data values (outliers) !from the rest of the boxplot. Extreme observations ibetween 1.5 and 3 times the interquartile range are !plotted individually with an asterisk (outside values). 'Observations greater than 3 times the interquartile 'range are distinguished by plotting them with a small ,circle (far-out values). The width of the box has no !particular meaning in boxplots. Further information Ion boxplots is contained in Helsel and Hirsch (1992). 8 Evaluation of Streamflow Traveltime and Streamflow Gains anll LOBBes along the Lower Purgatoire River, Southeastern Colorado, 1984-92