21 

 1 981 to 1 991 (90% confidence level). The boron Increase, as calculated by the Seasonal 



Kendall Sen Slope Estimate, is approximately 0.0250 mg/Uyear. As with TDS, this trend 



may be explained by the drought conditions in addition to consumptive use of water for 



cooling and natural evaporation from Cookson Reservoir. 



3.5.3 Other Water Quality Variables 



Table 3.1 contains the multipurpose water quality objectives for the East Poplar River at 

 the International Boundary, recommended by the International Poplar River Water Quality 

 Board to the IJC. One exceedence of the multipurpose objectives occurred in 1 991 . The 

 4.0 mg/L objective for dissolved oxygen was exceeded for an Environment Canada 

 sample collected on January 15, 1991 (2.5 mg/L). It is believed that the extensive ice 

 cover coupled with low flow conditions drastically inhibited the aeration process. 



Environment Canada monitored the East Poplar River for phenoxyacid herbicides and 

 organochlorine compounds during 1991. Trace concentrations of 2,4-D (in two of nine 

 samples), gamma-BHC (in one of nine samples), alpha-BHC (in three of nine samples), 

 and Dicamba (in one of nine samples) were recorded. The presence of these compounds 

 in prairie surface waters is well documented (Integrated Environments Ltd., 1991). All 

 other organic compounds monitored were below analytical detection limits. 



