- 10 - 

 SURFACE WATER QUALITY 



East Poplar River 



The 1981 report by the IJC to Governments recommended: 



For the March to October period, the maximum flow -weighted 

 concentrations should not exceed 3.5 mg/L for boron and 

 1500 mg/L for total dissolved solids for any three con- 

 secutive months in the East Poplar River at the Interna- 

 tional Boundary. 



For the March to October period, the long-term average of 

 flow-weighted concentrations should be 2.5 mg/L or less for 

 boron, and 1000 mg/L or less for total dissolved solids 

 in the East Poplar River at the International Boundary . 



For the period prior to 1982, three-month moving flow-weighted 

 concentrations (FWC) for boron and total dissolved solids (TDS) have 

 been calculated solely from monthly monitoring results. Since the 

 beginning of 1982, the USGS has monitored specific conductance daily 

 in the East Poplar River at the International Boundary, allowing 

 estimates of daily boron and TDS concentration to be derived from 

 regression relationships with specific conductance. Thus, three- 

 month FWCs for the period 1982 to 1988 have been calculated from 

 both the results of monthly monitoring and the daily concentration 

 estimates . 



The Bilateral Monitoring Committee has adopted the approach that 

 for the purposes of comparison with the proposed IJC long-term ob- 

 jectives, the boron and TDS data are best graphically plotted as 5- 

 year moving flow-weighted concentrations which are advanced one month 

 at a time. Prior to this year, long-term averages were calculated 



