13 

 3.5 Water Quality 



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 milligrams per litre (mg/L) for boron 

 and 1500 mg/L for TDS for any three consecutive months in the East Poplar 

 River at the International Boundary. For the fi/farch 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 TDS in the East Poplar River at the 

 International Boundary. 



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

 (FWC) for boron and TDS were calculated solely from monthly monitoring results. Since 

 the beginning of 1982, the USGS has monitored conductivity 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 conductivity. Thus, 

 three-month FWCs for the period 1 982 to 1 988 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 purpose of 

 comparison with the proposed IJC long-term objectives, the boron and TDS data are best 

 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 



