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<br />~ <br /> <br />0754 <br /> <br />Even if no losses or gains occur in a reach of channel, the shape <br />of an upstream hydrograph will be modified downstream by the storage <br />characteristics of the channel. The effect of channel storage can be <br />determined by various routing methods. In a recent study, Sauer (1971) <br />successfully used the unit-hydrograph technique to route releases from <br />Toledo Bend Reservoir to three locations as far as 50 miles down the <br />Sabine River on the Texas-Louisiana State line. <br /> <br />Channel Storage <br /> <br />As part of the Sabine River study, a computer program was developed <br />which routes reservoir releases by the unit-hydrograph technique. This <br />program was used to determine the effects of channel storage along the <br />Arkansas River from Granite to Avondale (fig. 2), The hydrographs at <br />the Granite gaging station for eight actual reservoir releases were <br />routed approximately 170 miles downstream by means of the program. The <br />releases selected for study included a variety of release discharges <br />and antecedent river conditions. The results of this analysis were used <br />to define channel storage as a function of time. This relationship is <br />shown in figure 4. Figure 4 shows that although the rate at which <br />release water enters channel storage is initially high, it decreases <br />rapidly with time and ceases in from 7 to 31 hours depending on the <br />amount of the release. Figure 4 also gives a table which summarizes <br />the average channel storage for selected time intervals. <br /> <br />. <br /> <br />Bank Storage <br /> <br />If the alluvium and river are hydraulically connected, an inter- <br />change of water is possible. For example, if the stage of a river <br />increases, flow which normally occurs from the alluvium to the river <br />may be reversed, and bank storage occurs. <br /> <br />Two approaches to define bank storage during reservoir releases <br />were investigated. The first approach was to study streamflow gains <br />and losses before and during a reservoir release. The second approach <br />waS to monitor head changes in observation wells near the river as a <br />release passed. <br /> <br />Gain-loss studies <br /> <br />During August 28-31, 1970, in the reach from Turquoise Lake to the <br />Arkansas River at Nepesta gaging station, gain-loss investigations were <br />conducted within 36 hours before and 24 hours after the passage of a <br />392-ft3/s release to Colorado Canal. The study involved measurement of <br />235 inflows, 58 outflows, 15 miscellaneous mains tern sites, and 12 main- <br />stem gaging stations. The flow at each mainstem gaging station was inde- <br />pendently measured by two hydrographers to insure accurate determination <br />of river flow. The same procedure was used during a second series of <br /> <br />. <br /> <br />11 <br />