3 



to December 31, 1982 was 0.076 m /s, well above the recommended flow of 



0.057 m /s for that time period. During the year the recorded flow was 

 below the recommended minimum flow approximately 19 percent of the time. 

 However, the average flow for each of the three periods exceeded the recommended 

 minimums. 



The hydrograph of the East Poplar River at the International Boundary is 



depicted in Figure 1, along with the International Joint Commission recommended 



minimum flows. As can be noted from the hydrograph, there was a large and 



3 

 sustained snowmelt runoff during I982. Of the total volume of 29,000 dam 



3 

 recorded for the year, 22,500 dam occurred in April. 



Reservoir Storage 



Cookson Reservoir Was at elevation 751.867 m on January 1, rising to 753-026 m 

 during the peak of the snowmelt runoff on April 15. The reservoir level was 

 held steady, near full supply levels for several months with the highest 

 level for the year recorded on June 2 at elevation 753-160 m. The reservoir 

 declined slightly over the summer months and the reservoir level at year end 

 was 752.681 m. The corresponding volumes of stored water were: 



Full Supply Level 43,^00 dam^ (elevation 753-000 m) 



3 

 January 1 35,000 dam 



April 15 't3,600 dam^ " 



3 

 June 2 44,700 dam-^ 



3 

 December 31 41,000 dam"^ 



3 

 The increase in storage over the year was 6,000 dam , with only small reservoir 



drawdown in the summer and fall, primarily because coal-seam dewatering dis- 

 charge entering Cookson Reservoir through Girard Creek was of sufficient 

 volume to help offset evaporative losses and releases from the reservoir. 

 Because of the near full supply level conditions at the end of the year, the 

 reservoir will not have a major modifying influence on the I983 spring runoff 

 in the East Poplar River. 



