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<br />. <br /> <br />w <br />~ <br />..t::- <br />c.n' <br /> <br />. <br /> <br />. <br /> <br />Inflow to Lake Powell. - With regard to inflow to Lake Powell, the <br />relationships between the 1976 present modified salt load and flow at the <br /> <br />four gaging stations measuring inflow into Lake Powell were analyzed to <br /> <br /> <br />determine if significant changes in the relationships had occurred during the <br /> <br /> <br />1941 through 1976 period. <br /> <br />Results of the study show that for the Colorado River, there is a 90 <br />percent or greater probability that the salt load versus flow relationship <br />for the 1968 through 1976 period is different than the relationship for the <br />1941 through 1967 period. These studies also indicate the change in relation- <br />ship began in 1968. For a virgin flow of 14 million acre-feet per year, the <br />estimated salt load to Lake Powell is 363,000 tons less when based on the <br /> <br />1968 through 1976 relationship than when based on the 1941 through 1976 <br />relationship. <br />For the Green River, the salt load versus flow relationship during 1941 <br />through 1976 has periods of relatively higher salinity followed by periods of <br />relatively lower salinity. The relationship resulted in a lower level of <br />salinity for the period 1970-1976. Because of this variable nature of the <br />relationship, the period of record is too short, however, to determine <br />whether a statistically significant change in relationship has actually <br />occurred and whether the recent lower trend will continue into the future. <br /> <br />Until additional data become available, it was assumed that the relationship <br /> <br /> <br />has not changed and the relationship based on the entire 1941-1976 period of <br /> <br /> <br />record was used for the 1981 review. <br /> <br />Slight increases in salinity after 1962 are indicated for the San Juan <br /> <br />River. However, statistical analyses indicate the periods before and after <br /> <br />1962 are not significantly different. Therefore, as with the Green River, it <br /> <br />15 <br /> <br />,;11 <br /> <br />" <br /> <br />.!illiI <br /> <br />1, <br /> <br />-, -"- -" <br />