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<br /> <br />(~ <br />) <br />~ <br />lv <br />J <br />~ <br /> <br />172 <br /> <br />Base-line irrigation depletions are taken from the Compre- <br /> <br />hensive Framework Study (1971; Table 5, p. 57). Higher levels of <br /> <br />irrigation depletions are taken from Ribbens and Wilson (1973; Table X). <br /> <br />5.5.1.4 Total Dissolved Solids Loading from Irrigation Return Flows <br /> <br />As described in Section 5.2.2, increases in total dissolved <br /> <br />solids loading due to irrigation return flows are modeled as a function <br /> <br />of the acreage irrigated. Further, only return flows from irrigation <br /> <br />above the base-line conditions must be considered, as stated in Section <br /> <br />3.3.2 and again in Section 5.2.2. Increases in irrigated acreage for <br /> <br />each depletion level are obtained from Ribbens and Wilson (1973; Table <br /> <br />~. <br /> <br />5.5.1.5 Side Inflows above Lake Powell <br /> <br />Ungauged side inflows of water and salt are modeled as constant <br /> <br />monthly inputs to the river system. These inputs are treated as con- <br /> <br />tro1 variables so that adjustments for depletions and salinity control <br /> <br />projects affecting these flows may be imposed. <br /> <br />The sources of information for base-line conditions have <br /> <br />been given in Tables 5.1 and 5.2. As indicated in Section 5.3, <br /> <br />modeled side inflows of salt have been adjusted upward to correct for <br /> <br />the observed imbalance in Table 5.1(b). <br /> <br />Side inflows of water and salt above Lake Powell are displayed <br /> <br />in Tables 5.5 to 5.8 for each level of depletion. Depletion levels <br /> <br />DPL #l to DPL #3 exhibit a side inflow of water greater than the base- <br />