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C) Colorado River near CO-UT State Line <br />W 500 <br />E <br />- 400 <br />m <br />300 <br />W <br />r <br />u <br />a 200 <br />D <br />100 <br />e <br />c 0 <br />Q <br /> <br />a <br />12.0 <br />c <br />m <br />8.0 0 <br />m <br />CL <br />4.0 <br />0 <br />0.0 - <br />1930 1940 1950 1960 1970 1980 1990 2000 <br />d) Colorado River near Cisco, UT <br />600 <br />71 <br />E <br />m 400 <br />E, <br />W <br />L <br />u <br />200 <br />W <br />7 <br />C O <br />G <br />Q <br />1930 <br />a <br />16.0 <br />c <br />m <br />12.0 <br />0 <br />8.0 n <br />4.0 ° <br />0.0 <br />1940 1950 1960 1970 1980 1990 2000 <br />Figure 14 (cont.). Trends in annual discharge and suspended sediment load at the (c) State Line and <br />(d) Cisco gauges. Horizontal lines indicate means for the periods 1934-1958 and 1959-1997. <br />The results of the Mann-Whitney tests (Table 6) show that since 1934 there has been no significant <br />change in the mean annual discharge of the Colorado River; this is indicated by the low values of <br />the test statistic, z, and the high values of the significance probability, p. This result is potentially <br />misleading, however, because it does not take into account the effects of transbasin diversions, many <br />of which were in place prior to 1934. <br />Turning to the comparisons of sediment loads, the test results indicate that there have been <br />significant changes in the average annual suspended sediment load of the upper Colorado River <br />since the late 1950s (p values ranging from 0.002 to 0.02; Table 6). Interestingly, the difference <br />between pre- and post-1958 sediment loads decreases downstream, from 40% at the Glenwood <br />Springs gauge to about 25% at the Cisco gauge. This trend likely reflects a combination of the <br />25