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<br />(~;') <br />.-..) <br />I\~ <br />t-'" <br />00 <br />""'-l <br /> <br />155 <br /> <br />data. Discrepancies are on the order of at most 5%, within the <br /> <br />accuracy of estimates and measurements. <br /> <br />Table 5.1(b) displays a balanced salt budget, balanced to within <br /> <br />+ 8% over the period 1941 to 1962. The modeled stream salinities <br /> <br />were calculated as a function of the measured streamflow using the <br /> <br />stream salinity subroutine. Estimates of side inflows of salt were <br /> <br />made from USBR information (USBR, 1971a). Estimates of changes in <br /> <br />salt stored in Lake Mead were made using discharge concentrations and <br /> <br />initial and final total storage values. The discrepancy between the <br /> <br />actual and modeled outflow of salt from Lake Powell is removed from <br /> <br />subsequent simulation runs by adjusting the contribution from side <br /> <br />inflows upward (see Table 5.5). <br /> <br />1963-1968 <br /> <br />The water and dissolved solids budgets for the period 1963-1968 <br /> <br />are shown in Table 5.2(a,b). The difference between the measured <br /> <br />change in Lake Powell storages and the modeled change in storage is <br /> <br />presumably the amount lost to bank storage during the filling of <br /> <br />Lake Powell. This difference represents a 23% error in the estimate <br /> <br />of accumulated surface storage. The aggregate difference between <br /> <br />measured and modeled changes in Lake Mead Surface storage is 7.7%. <br /> <br />The difficulties in forming a mass balance of dissolved solids <br /> <br />for the 1963 to 1968 period are compounded by the filling of Lake Powell <br /> <br />(Hoffman, 1967). <br /> <br />Effects of initial filling upon downstream <br /> <br />water quality are difficult to ascertain (USBR, 1971a). The modeled <br /> <br />discharge of salts from Lake Mead is not as well reproduced by the <br /> <br />