3.2.5 Water-Quality 



The 1981 report by the UC 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/Lfor 

 TDS 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 TDS 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 TDS were calculated solely from monthly monitoring results. Since the beginning of 1982, 

 the US 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 the regression relationship with specific conductance. Thus, three-month FWCs 

 for the period 1982 to 1995 have been calculated from both the results of monthly monitoring and 

 the daily concenfration estimates. 



The Bilateral Monitoring Conmiittee adopted the approach that for the purpose of comparison 

 with the proposed UC long-term objectives, the boron and TDS data are best plotted as five-year 

 moving FWCs which were advanced one month at a time. Prior to 1988, long-term averages were 

 calculated for a five year period in which 2.5 years preceded and 2.5 years followed each plotted 

 point. Beginning in 1988, FWCs were calculated from the five year period preceding each plotted 

 point. For example, the FWC for December 1995 refers to the FWC of the period December 1990 

 to December 1995. The calculations are based on the results of samples collected throughout the 

 year, and are not restricted to only those collected during the months bracketing the period of 

 irrigation (March to October) each year. 



