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Boron 



During 1987, boron concentrations in the East Poplar River at the 

 International Boundary varied from 1.4 mg/L (May 19) to 2.2 mg/L 

 (August 5) (Figure 7). 





• • • 





Figure 7. 1987 Boron Grab Sample Data, East Poplar River at 

 International Boundary 



Three-month flow-weighted boron concentrations using grab sample 



and regression computed data for the period of record are shown in 



Figure 8. The relationship between boron and specific conductance 



at the East Poplar River sampling location during the period 



1975-1987 is described by the equation: 



Boron = (0.00146 X specific conductance) - 0.277 

 r2=0.73, n=322) 



The short-term objective of 3.5 mg/L boron has not been exceeded in 

 the period 1975-1987. The effect of flow is evident in low boron 

 concentrations occurring during the high spring flow events of 

 1976, 1979, 1982, 1983 and 1986. A trend in boron concentrations 

 is not discernible in the historical data base. 



The five-year flow-weighted concentrations are presented in 

 Figure 9 . The five-year flow weighted concentrations remain well 



