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As stated previously, a residual results from the mass - balance calculations done by PWAP. It <br />cannot be avoided due to uncertainties in the input data and the exclusion of direct rainfall, <br />unmeasured tributary inflow, and potential seepage losses and bank storage. <br />In PWAP, if the residual is a gain, it is credited completely to natural flow water. If the residual <br />is a loss, it is distributed proportionately to the natural flow, storage, and environmental account <br />water. <br />Graphs showing the number of gaining and losing months during 1982 to 1999 for selected <br />reaches can be found in Appendix B. <br />South Platte River <br />Until now there has not been a need to track natural flow and either storage or environmental <br />account water in the South Platte River. Therefore, before the South Platte River can be added to <br />PWAP, travel time and CL estimates must be established. <br />River Geography <br />There are three gages that could be used in PWAP on the South Platte River. They include the <br />gages at Julesburg, Roscoe, and North Platte. <br />A time of travel study was completed for the South Platte River between the Julesburg and the <br />. North Platte. It was found that it took approximately 22 hours for a pulse of water to travel from <br />Julesburg to Roscoe and an additional 30 hours to travel from Roscoe to North Platte (graphs <br />showing the results can be found in Appendix Q. The river distance between Julesburg and <br />Roscoe is approximately 36.4 miles and the distance between Roscoe and North Platte is <br />approximately 47.8 miles. The average velocities in each reach are 0.60 miles per hour (mph) <br />and 0.63 mph. Because of the coarseness of the input data, they are essentially equal. Therefore <br />it appears that a gage site near the Korty Diversion Dam (approximately 6 miles downstream of <br />Roscoe) would be closer to the middle point between the Julesburg and North Platte gages and <br />would more closely approximate a daily time step. It is approximately 42.2 miles upstream to <br />the Julesburg gage and 42.0 miles downstream to the North Platte gage. Until a change can be <br />made on the location of the intermediate gage it is recommended that there be two reaches on the <br />South Platte River for use in PWAP. <br />• Julesburg to Roscoe <br />• Roscoe to North Platte (Confluence with the North Platte River) <br />• <br />Conveyance Losses <br />The conveyance losses were calculated in the same manner as on the North Platte and Platte <br />Rivers. The results are shown in the following table. <br />2 <br />