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<br />. <br /> <br />. <br /> <br />l\j <br />~ <br />w <br />co <br /> <br />Statistical Analysis' <br /> <br />Step 1. ~'Preliminary examination of variables: <br /> <br />Variabl~s which will be considered in the statistical analysis include <br />time, s~reamflow, and the concentration, load, and mass fraction of <br />individUal ionic solutes. Time will be defined as a discrete variable <br />with uni!ts of months, beginning with the first month in the period of <br />record. . Average monthly discharge (Qm) and solute concentrations <br />(Cim) willl be obtained from the data base. Solute loads (Jim. Kg/s) <br />and mas~ fractions (Pim) will be calculated <br /> <br />Jim = Cim * Qm <br /> <br />)!} <br /> <br /> <br />Cim <br />Pim = TDSm <br /> <br />where TDS~ is the average monthly concentration of total dissolved solids <br />obtained, by summation of the six solute concentrations (eim)' <br /> <br />Plots wi11 then be generated for the entire time series of variables Cim' <br />Om. Jim,! and Pim' Mean values and standard deviations will be computed <br />for each' variable. Monthly values more than two standard deviations from <br />the mean' will be 1 i sted as out1 iers but wi 11 not be exc1 uded from the data <br />.set. If, the plots indicate a step change for any variable, means will be <br />recomput~d for the periods before and after the change and the significance <br />of the'change tested by comparison of means. If the change is significant, <br />the before and after time periods will be evaluated separately in steps 2 <br />through Ii. <br /> <br />.. <br /> <br /> <br />Step 2. - Analysis of seasonal variability: <br /> <br />The complete data set will then be used to identify seasonal variations. <br />Mean values and standard deviations will be computed for each variable by <br />calendar;month (January, February, etc.). Again, values more than two <br />standardjdeviations from the mean will be listed as outliers. <br /> <br /> <br />-L <br /> <br />~ ,.~, ,.1. &':i'_ <br /> <br /> <br />6 <br />