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<br />OO~834 <br /> <br />at Imperial Dam since there are no dampening effects. Erratic <br />ungaged inputs produce large variances at Imperial but have a <br />smaller impact on upstream stations, indirectly affecting salin- <br />ities by altering releases from upstream reservoirs. <br /> <br />Replacing month-by-month ungaged inputs in the Parker-Imperial <br />reach by a single annual cycle reduces the variance significantly <br />at Imperial Dam and slightly increases those upstream. <br /> <br />Replacing month-by-month target flows by a single annual pattern <br />reduces the variance at every station. <br /> <br />Although the variance of Run No. 31 compares most closely with present <br />modified data, Run No. 32 was used as the base run for adding future <br />developments. It was used because future target flows at Imperial Dam <br />are likely to be very regular as a consequence of complete control of <br />the river and full basin development. Plots of the reservoir volumes <br />and salinities are given in Appendix D. <br /> <br />Effect of Averaging Data <br /> <br />In general, averaging time-dependent hydrologic data over longer <br />and longer time periods reduces the variance for the entire period. <br />Several runs, made during development of the base run, illustrate <br />this fact. Results for Imperial Dam are presented in Table VII for <br />the following conditions: <br /> <br />Run No.6 - Month-by-month values for all ungaged tributary inputs. <br /> <br />Run No. 9 - A single annual cycle of monthly percentages was used <br />to distribute annual totals. Percentages were computed using mean <br />monthly values. <br /> <br />Run No. 7 - A single annual cycle of monthly values, equal to the <br />means, was repeated for each year. <br /> <br />Results at Imperial Dam are used because they represent the integrated <br />effect of all upstream activities. Although the same total mass of <br />salt and water is input for each ungaged tributary, changes in the <br />sequence of inputs as well as storage changes account for different <br />mean concentrations. Time- and flow-weighted concentrations are Seen <br />to decrease with more averaging. The fact that the standard deviation <br />increases when an annual percentage distribution is used is somewhat <br />surprising. However, when the single annual cycle of monthly values <br />is used, the variance is radically reduced. <br /> <br />It should be noted that these results are only presented to support <br />general observations. They are based on runs in which Lakes Mohave <br /> <br />24 <br />