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<br />001321 <br /> <br />Positive water quantities and salt masses denote additions to the river <br />system while negative values represent depletions. The sign of the con- <br />centrations depends on the sign of both the water and salt mass. A pos- <br />itive sign means the masses have the same sign while a negative denotes <br />opposite signs. By convention, concentrations are set to zero when <br />flows are zero, even though there may be a computed salt mass. However, <br />in making the computer runs, both the computed water and salt masses are <br />applied, regardless of magnitude or sign. ' <br /> <br />Lake Powell Reach <br /> <br />Inflows to the Lake Powell reach are the four upstream boundary sta- <br />tions on the Colorado, Green, San Rafael, and San Juan Rivers. Out- <br />flows are reflected by the unregulated Lees Ferry data. \~en the <br />mean evaporation amounts are added to the Lees Ferry values, all <br />reservoir effects have been removed, data reflect river reach condi- <br />tions, and the standard procedures for a reach without storage are <br />used. <br /> <br />It was previously noted that unregulated flows may exceed the outlet <br />works capacity. By considering Lees Ferry flows in Appendix A and <br />the maximum capacity of Table I, it is noted that the capacity is <br />exceeded for the following months: <br /> <br />April 1942, 1962 <br />May 1942-l945, 1947-1949, 1952, 1957, 1958, 1962, 1965, 1969, <br /> 1970 <br />June 1942-1953, 1956-1958, 1962, 1965, 1967, 1968, 1970 <br />July 1957, 1965 <br /> <br />An inspection of Figures C-2 and C-3 along with the corresponding <br />tabulations reveals a distinct change in the character of ungaged <br />salinities in 1963. The series for the 1963-1970 period are mark- <br />edly different from the 1941-1962 period. This is not apparent for <br />flows, Figure C-l. The most readily identified event occurring in <br />1963 was the closure of Glen Canyon Dam and the initial filling of <br />Lake Powell. Table C-4 and Figure C-4 present the historic end-of- <br />month contents. This suggests that while historic data were cor- <br />rectly modified to account for the change in storage of water, <br />corresponding adjustments for salts were not included. <br /> <br />In an effort to improve ungaged salinities for 1963-1970, the <br />ungaged salt mass was correlated with the corresponding flows for <br />the 1941-1962 period. If a reasonable correlation existed, then <br />1963-1970 data could be generated from the regression equation. <br />Results for a fourth-degree polynomial are presented in Figure C-7. <br />The correlation, obviously very poor, produced a coefficient of <br />determination of 0.11, forcing abandonment of this approach. <br /> <br />II <br />