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<br /> <br />000892 <br /> <br />~ <br />. <br />. <br />. <br />. <br />-- <br />- <br /> <br />then used as a guide in selecting independent variables. In <br />this manner a prediction equation was designed to maximize <br />physical meaning and statistical accuracy. <br /> <br />Selection of an Annual Regression Equation. <br /> <br />Lengthening the sample of the dependent variable and <br />one of the independent variables was first examined. The <br />dependent (predicted) variable, purgatoire River flow at <br />Thatcher (Qth) and a potential independent (predictor) vari- <br />able, Van Bremer Arroyo flow (Qvb) have a period of record <br />only since 1967 as a result of the 1965 Model transfer <br />decree. Extension of Qth back to 1925 was possible by cor- <br />relation with flows of the Purgatoire River at Trinidad <br />(Qtr) and Ninemile Dam near Higbee (coefficient of multiple <br />correlation, R=O.97). A similar extension was not possible <br />for Qvb. <br /> <br />Initial multiple linear regressions (MLR's) involved <br />the lengthened record for the predicted variable, Qth- <br />Unfortunately, the best MLR's computed for the long record <br />included diversions to project ditches. The problems with <br />the lengthened record MLR's were threefold: <br /> <br />1. The statistical population of project ditch diver- <br />sions has changed since Trinidad Reservoir opera- <br />tion beganl diversions cannot be used as an <br /> <br />-15- <br />