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<br />. <br /> <br />k <br />W <br />'J <br />c..:-' <br /> <br />. <br /> <br />. <br /> <br />NOTES <br /> <br />Tables 1 through 20 <br /> <br />The historical flo", and quality of ",ater data have been recalcu- <br />lated using the U.S. Geological Survey WATSTORE data base and computer <br />techniques developed jointly by Reclamation and the USGS. The purpose <br />of the ne", analysis is to develop a consistent, documentable methodology <br />for the calculation of monthly salt loads in the Colorado River Basin <br />and to computerize the preparation of the tables. <br /> <br />The method "'as originally developed for the trend studies recently <br />conducted by Reclamation and the USGS. Several procedures ",ere evalu- <br />ated. A 3-year moving regression ",as determined to be the best overall <br />method in terms of providing the most complete record, preserving short- <br />term fluctuations, and being insensitive to minor errors in the data. <br />Using this method, daily salt load (L) was computed from discharge (Q) <br />and conductivity (S): L = aQbSc, <br /> <br />The coefficients a, b, and c for each year of record were estimated <br />by regression analysis using data from a 3-year period. For example, <br />coefficients for 1975 "'ere derived with data from 1974-76.1' For days <br />without specific conductivity data, an equation for load as a function <br />of discharge alone is also evaluated: L = a'Qb' <br /> <br />Daily loads were added to yield the monthly values given in Tables <br />1 through 20. Monthly values were then added to yield annual values. <br />All values shown in Tables 1 through 20 are rounded but were computed <br />using unrounded values. <br /> <br />For this analysis, salt load data were based on TDS as the sum of <br />constituents, whenever possible. Sum of constituents was defined to <br />ioe lude calciumi magnesium, sodium, chloride J suI fate, some measure of <br />carbonate (C03- plus the carbonate equivalent of HC03- or the carbonate <br />equivalent of alkalinity) and, if measured, silica and potassium. If a <br />sum-af-constituents value could not be computed, TDS as residue on <br />evaporation (at 1800 C) was substituted. <br /> <br />Extensive error analyses ",ere performed on the WATSTORE data. Sus- <br />pect values were corrected according to published records or deleted. <br />The resultant data set is considered by Reclamation and the USGS to be <br />the best available for stations in the Colorado River Basin. <br /> <br />Annual values based on the new method were compared to values in <br />previous Quality of Water Progress Reports for selected stations. The <br />observed di fferences were between .::.5 percent, wi th mean di fferences <br />approximately zero. Changes in the progress report data base can, there- <br />fore, be considered generally insignificant and unbiased. <br /> <br />11 Since 1984 data were unavailable, the 1983 analysis is pre- <br />limi nary. <br /> <br />139 <br />