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~- 00 ~I"') (~. . _.- :,-. .--h. -....: . of mean EC and mean TDS. The results are represented in Table 41 by runs El through E4. The coefficients for run ES are from the previously mentioned 1976 USGS report. These coefficients differ from the Bureau's somewhat because of 3 reasons. First, they are based on a smaller period of record. Secondly, they don't include Bureau data. In the third place, they are based on TDS calculated by the residue method. The TDS values used by the Bureau in this report for the regression equations and all salt loading computations represent TDS calculated by the method of sum of constituent:s. Where TDS by sume of constituents was not available, TDS by residue was c,)nverted to an equivalent sum of constituents value according to a correlation between residue and sum of constituents TDS values in Grand Valley. . Finally, the sensitivity of the mean annual loading to different types of available data was examined and the results presented in Table 42. It is interesting to note that the results are insensitive to the type of available data. In fact, simply interpolating between grab samples (run F4) yields nearly the same mean loading (at least for this station which is on a highly regulated river), as using all the data (run 0). Overall, the sensitivity of the estimated of Cameo's mean annual salt loading appears to be very low. It is believed that the loading estimates of all the river stations used in this report are similarly insensitive. The loading estimate for stations with less data or unregulated watercourses would probably be much more sensitive. At any rate, the insensitivity of the mean . annual salt loading should lend some confidence to the mean annual salt pickup estimate presented in this report. A-12