27 



_j 756 



^ 755 



LlJ 



_l 754 



^ 753 



> 751 



^ 750 



in 749 



^ 748 



^ 747 



Z 746 



2 745 



O 744 



^ 743 



y 742 

 ^ 741 



T 1 1 1 1 1 1 1 1 I f 



Full Supply Level 



missing data 



\ 



'Minimum Desired Operating Level 



'Unusable Storage Level 



MEAN DAILY WATER LEVEL FOR 1 992 



MEDIAN OF MONTHLY MEAN ELEVATION FOR 1 981 -1 991 



JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 



1992 



Figure 3.13 Cookson Reservoir Mean Daily Water Levels for 1992 and Median 

 Monthly Water Levels for 1981-1991. 



3.4.2 Water Quality 



For the last several years, the lack of normal spring runoff has been the most significant factor 

 influencing Cookson Reservoir water quality. During 1992, Cookson Reservoir did not experience 

 boron concentrations in excess of 3.5 mg/L However, the reservoir water quality exceeded 1 500 

 mg/L for total dissolved solids. 



The net effect of little spring runoff over the last several years has been a decrease in reservoir water 

 quality. From 1988 to the end of 1992, several analytes have doubled in concentration; sulfate, 

 sodium, and boron, for example. The reservoir water quality has decreased to the point that a 

 substantial spring mnoff will be required to have any significant impact on the reservoir quality. 



