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<br />OJJlfrO <br /> <br />SECTION III <br /> <br />RIVER CHANNEL HYDRAULICS <br /> <br />A starting point for the determination of travel time and transit loss <br />is with the river channel hydraulic characteristics and the adjacent geography <br />and geology, for it is this aspect of the river which has the most effect upon <br />the rate of flow and the stream losses and their determination. The study of <br />the river hydrographs at the various gaging stations throughout the study reach <br />is similar in many respects to reviewing electro-cardiographs. The hydrographs <br />themselves provide a source of extensive knowledge of channel hydraulics, and <br />their analysis in regard to time, volume and rate of flow can provide an inte- <br />grated picture of a given river run under given specific conditions. However, <br />there is a need for interpolations and interpretations for the projecting of <br />results under previous ungaged conditions, and it is because of this that spe- <br />cific knowledge on the detailed character of the river channel is important. <br /> <br />In this Section of the report, information is presented and observations <br />noted which should be of particular value to future hydrologists as additional <br />studies of the Arkansas River are undertaken to further upgrade the accuracy of <br />the travel time and transit loss studies. <br /> <br />GENERAL <br /> <br />The flow conditions in the Arkansas River between Leadvil Ie and Pueblo <br />can in general be described as unsteady and non-uniform. Tributary inflow, <br />diversions, evaporation and seepage-,_ combined with almost continuous changes <br />in cross sections, make the flow non-uniform except over very short reaches <br />of river channel. Stream flow recorder charts indicate that there are periods <br />of a day or more in duration during which there is little or no change in stage, <br />which would indicate steady flow conditions. However, for time periods in <br />excess of a day, the flow is generally unsteady. Diurnal variations in stream <br />flow are often evident, especially during the spring time at the upstream gages. <br /> <br />The flow characteristics of the Arkansas upstream from Canon City can be <br />described as swift and turbulent with numerous rapids and pools. The channel <br />slope in this reach is hydraulically steep. Downstream from Canon City the <br />river becomes tranquil; the channel remains relatively well-defined, with an <br />increase in the amount and degree of meandering. The channel slope in this <br />reach is hydraulically mild. <br /> <br />Reservoir releases made in the Leadville region generally result in rapid <br />increases in river discharge which approximate gravity waves. The celerity <br />of these waves as they travel downstream exceeds the mean velocity of water <br />within the channel by a factor of about 1.3. The apparent wave front velocity <br />would be higher if there were not so many channel storage requirements in side <br />pools, behind bridges, etc. <br /> <br />19 <br />