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("1""1 uo{..' Reach 1 Reach I extended 60.6 mi from site QI (Purgatoire River below Trinidad Reservoir) to site Q2 (Purgatoire River near Thatcher) (fig. I). Review of hourly streamflow data for sites QI and Q2 did not result in any suitable streamflow events to estimate traveltimes for reach I. The reasons for this lack of suitable streamflow largely are due to the substantial effects of diversions to canals and unmeasured return flows in this irrigated study reach. The irrigation canals can return unmeasured quantities of water back to the river a short distance downstream from the diversion structure; parts of these return flows, as well as unmeasured return flows from the irrigated areas, then are diverted by the next downstream irrigation canal. Therefore, a qualitative and quantitative comparison of streamflow hydrographs at sites QI and Q2 did not result in an estimate of traveltime for reach 1. Because the hourly data could not be used successfully in estimating traveltimes in reach I, daily mean streamflow data collected between January 1957 and December 1967 were analyzed to see if travel- times could be estimated from additional streamflow data available at mainstem sites QIA, QIB, and Q I C and at tributary sites Tl and T2 (fig. I). However, the results were similar to those for the hourly data analysis, in that suitable streamflow events at site QIA could not be distinguished at the two downstream stations (sites QIB and QIC). Therefore, traveltime could not be estimated for reach 1. Reach 2 Reach 2 extended 40.1 mi from site Q2 (Purgatoire River near Thatcher) to site Q3 (Purgatoire River at Rock Crossing near Timpas) (fig. I). Analysis of hourly streamflow records compiled between 1990 and 1994 resulted in selection of 31 suitable streamflow events to estimate travel- time. For reach 2, the relation of traveltime to the instantaneous peak streamflow at site Q2 is shown in figure 7A. Traveltime in reach 2 generally increased as the streamflow in the reach decreased, but travel- time also varied for a specific streamflow (fig. 7). Traveltime variation for reach 2 might have occurred because of different antecedent river conditions that existed prior to each streamflow event. The travel- times computed for reach 2 ranged from about II to about 47 hours, with 23 of the 31 instantaneous streamflow peaks within 12 hours of I day (fig. 7). A regression analysis indicated that streamflow and traveltime were significantly related (p=O.OOOI) in reach 2, and about 70 percent of the variation that was observed in the traveltimes could be explained by streamflow. Streamflows greater than 100 ft3/s at sites Q2 and Q3 were infrequent (fig. 6). Most of the traveltime estimates made for reach 2 were computed for instantaneous peak streamflows greater than 100 ft3/s. However, there were five streamflow events selected with instantaneous peak flows less than 100 ft3/s, and their traveltimes through reach 2 ranged from about 23 to about 47 hours (fig. 7). Reach 3 Reach 3 extended 58.5 mi from site Q3 (Purgatoire River at Rock Crossing near Timpas) to site Q4 (Purgatoire River near Las Animas) (fig. I). Analysis of hourly streamflow records compiled between 1990 and 1994 resulted in selection of 30 suitable streamflow events to estimate travel- time. For reach 3, the relation of traveltime to the instantaneous peak streamflow at site Q3 is shown in figure 7B. Traveltime in reach 3 generally increased as streamflow in the reach decreased, but traveltime also varied for a specific streamflow (fig. 7). Travel- time variation for reach 3 might have occurred because of different antecedent river conditions that existed prior to each streamflow event. The trawl- times computed for reach 3 ranged from about 6 to about 61 hours, with 22 of the 30 instantaneous streamflow peaks within 12 hours of I day (fig. 7). A regression analysis indicated that streamflow and traveltime were significantly related (p=0.0001) in reach 3; however, only about 40 percent of the variation that was observed in the traveltimes could be explained by streamflow. Streamflows greater than 100 ft3/s at sites Q3 and Q4 were infrequent (fig. 6). Most of the traveltime estimates made for reach 3 were computed for instantaneous peak streamflows greater than 100 ft3/s. However, there were five streamflow events selected with instantaneous peak flows less than 100 ft3/s, and their traveltimes through reach 3 ranged from about 43 to about 56 hours (fig. 7). STREAMFLOW TRAVEL TIMES 15