28 



1000 



800 



600 



O) 



E 



400 



200 



7 



— X- 



16 

 24 







Jan-80 Jan-83 Jan-86 Jan-89 Jan-92 Jan-95 



DATE 



Figure 3.12 Total Dissolved Solids in Samples from Montana Monitoring Wells. 



3.4 Cookson Reservoir 



3.4.1 Storage 



On January 1, 1994, Cookson Reservoir storage was 23 300 dam^--only 54 percent of the full- 

 supply volume. The 1994 maximum, minimum, and period elevations and volumes are shown in 

 Table 3.4. In addition to runoff, reservoir levels were augmented by ground-water pumpage. Wells 

 in the Supplementary Water Supply Project supplied 5 485 dam^ to Girard Creek. Approximately 70 

 percent of this flow volume reached Cookson Reservoir. Wells in the Salinity Control Project 

 supplied 1 090 dam^ directly to the reservoir. 



