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1981-90 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 

 consecutive months in the East Poplar River at the 

 International 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) were 

 calculated solely from monthly monitoring results. Since the beginning 

 of 1982, the U.S. Geological Survey (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 adopted the approach that for the 

 purposes of comparison with the proposed IJC long-term objectives, the 

 boron and TDS data are best graphically plotted as five-year moving FWCs 

 which were advanced one month at a time. 



Beginning in 1988, FWCs were calculated from the five year period 

 preceding each plotted point. Prior to 1988, long-term averages were 

 calculated from a five year period in which 2.5 years preceded and 2.5 

 years followed each plotted point. For example, the FWC for December 



