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Girard Creek and Cookson Reservoir 

 1981-1990 



The 1981-90 Cookson Reservoir data for TDS and boron collected prior to 

 freezeup conditions illustrate increasing trends. A review of concurrent 

 reservoir volumes and the declining trend over the past four years 

 suggest the low inflows may have exacerbated the upward trend. During 

 the same review period, the East Poplar and Girard Creek inflows 

 demonstrated annual variability but long term trends were not apparent. 



The major ion compositions in early winter samples collected in 1980, 

 1981, 1985, and 1990 from Cookson Reservoir near Morrison Dam and at 

 Highway 36, and Girard Creek were examined. The ionic characteristics 

 have remained generally similar although some subtle changes in 

 composition have occurred. The shifts have primarily related to the 

 magnesium, sodium plus potassium, bicarbonate and sulphate ions. 



Over the 1981-90 period, the water quality has essentially been within 

 the objectives established for the East Poplar River at the international 

 boundary (Table 5) . Apart from TDS and boron, percentile ranges and 

 trends for the remaining variables have been as listed in Table 5. 



