The 3-month moving FWC for TDS for the period of record is presented in Figure 3.5. The TDS 

 objectives have not been exceeded during the period of record. On inspection of the plot in Figure 3.5, it 

 is apparent that the 3 -month moving FWC increased gradually, year by year, up imtil the spring runoff 

 of 1997, when an exceptionally heavy snowmelt contributed sufficient water of low ionic strength to the 

 river and the reservoir to dilute the accumulated salts built up in the system. Dissolved-solids 

 concentrations were slightly higher in 2004 relative to those recorded in 2003. In general, low spring 

 runoff and higher contribution from ground water have kept the TDS concentrations close to the long- 

 term objective of 1,000 mg/L. 



The 5-year moving FWC for TDS (Figure 3.6) did not exceed the long-term objective of 1,000 mg/L in 

 2004. The maximum monthly FWC in 2004 was about 935 mg/L, which is slightly higher than the 2003 

 maximum monthly value of 887 mg/L, but lower than the maximum value of 943 mg/L reported in 

 2002. 



The daily TDS values, as generated by linear regression from the daily specific-conductance readings, 

 for the period January 1990 through December 2004 are shown in Figure 3.7. The data show an abrupt 

 drop in TDS corresponding to the snowmelt runoff occurring during the spring of each year. 



The relationship between TDS and specific conductance based upon data collected from 1974 to 2003 is 

 as follows: 



TDS = (0.62461 x specifle conductance) + 35.184 

 (R^ = 0.84, n = 617) 



Note: The above equation was used to derive the missing TDS water-quality sample data for 2004. 

 These derived data are used in the current annual water-quality report. 



11 



