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<br />, <br /> <br />M::>. <br />Cl <br />W <br />00 <br /> <br />RESULTS <br /> <br />The various model predictions regarding future TDS <br />levels in the Colorado River are based on the assumption <br />that TDS concentrations will vary inversely with flows. <br />Sufficient data were available to statistically evaluate <br />,these relationships at Lees Ferry and Grand Canyon during <br />!pre- and post-Lake Powell periods and below Hoover Dam dur- <br />:ing three post-Lake Mead periods. <br />: The flow vs. TDS concentration relationships developed <br />ifor these locations are presented in Table I. It was evident <br />: that TDS concentrations were inversely related to flows dur- <br />ling pre-Lake Powell periods at Lees Ferry and Grand Canyon. <br />I The correlation coefficients for these relationships were <br />: highly significant at each location (Table I). There was no <br />: apparent relationship between TDS concentrations and'flows <br />- ia~ Lees Ferry or Grand Canyon during the post-Lake Powell <br />: period (Table I). A similar situation existed below Hoover <br />Dam (Table I), even though annual flow variations were simi-' <br />lar in magnitude to those at Lees Ferry and Grand Canyon <br />during the pre-Lake Powell period. The lack of a relation- <br />!ship, or poor relationship, between TDS concentrations and <br />:flows during the post-impoundment periods indicated that <br />iother factors were operating in the impoundments to in flu- <br />; ence TDS. <br /> <br />Table I. Regression Equations and Correlation Coefficients <br />for Relationships Between Changes in Flows (X) and <br />TDS Concentrations (Y) for Various Time Periods and, <br />Locations in the Colorado River, (fiFlow Units as <br />m3 x 1010 and fiTDS Concentrations as mg/l) [USGS <br />Da ta ] . <br /> <br /> Time Regression <br /> Location Periods N Equations r <br /> a b x 10-10 <br /> : Lees Ferry 1951-60 9 Y- 0;53-151.712(X) -.852* <br /> : Lees Ferry 1970-79 9 Y= 4.40-110.844(X) -.384 <br /> , Grand Canyon 1926-42 16 Y= 4.66-211. 686(X) -.7861' <br /> . Grand Canyon 1951 -60 9 Y= -2.84-172.953(X) -. 894* <br /> . Grand Canyon 1970-79 9 Y= -4.92- 42.164(X) -.208 <br /> Hoover Dam 1935-43 8 y= -1.28- 11.391 (X) -.079 <br /> Hoover Dam 1951-60 9 y= -2.01-121.480(X) -.568 <br /> Hoover Dam 1970-79 9 y= 5.18- 6.297(X) -.011 <br />: *Significant at PC.01) <br />, <br />I <br /> <br />.6 <br /> <br />.. <br />