present the long-term trends in tlie data. The 5-year, moving f! 5w- 

 weighted concentration for boron does not exceed the 2.5 mg/L recom- 

 mended long-term objective. The maximum value for the period, 1975 

 to December 1984, is 1.46 mg/L, plotted for January 1979. 



Other Water Quality Characteristics 



Table 4 shows the multi-purpose water quality objectives recommended 

 by the International Poplar River Water Quality Board to the IJC. 

 The number of samples collected for each parameter by Canadian and 

 United States agencies is also shown. One dissolved aluminum concen- 

 tration of 0.11 rag/L was reported on the 17th of June. This single 

 value is not considered to be significant, however, as it is only 

 0.01 mg/L above the objective of 0.10 mg/L. Other than this one 

 anomalous value, the recommended objectives were met for the East 

 Poplar River at the International Boundary. 



The inverse relationship on the East Poplar River that existed 

 between specific conductance and streamflow prior to construction of 

 Cookson Reservoir remains, but has been modified somewhat as a result 

 of reservoir mixing and controlled releases. During periods of high 

 runoff, such as the spring freshet, the specific conductance de- 

 creases, as the proportion of streamflow derived from ground water 

 decreases. Conversely, during times of low streamflow (late summer, 

 winter) the contribution of ground water to streamflow is proportion- 

 ately greater. Because the natural ground water has a higher ionic 

 strength than does the surface water entering the river, the specific 

 conductance of the stream increases markedly during periods of 

 reduced flow. 



With the exception of a sample taken on August 8, 1984, the Environ- 

 ment Canada data indicated that the mercury content was at or below 



16 - 



