- 19 - 



The 

 6 



1986 spring runoff was about normal in volume (13.5 x 

 3. 



10" m~) which resulted in approximately one-quarter to 

 one-third of the reservoir volume being turned over. This had a 

 diluting effect on the reservoir and consequently improved its 

 water quality. 



The 1987 spring runoff was only 20 percent of normal and had little 

 influence in improving reservoir water quality. Full supply volvime 

 was not reached during 1987. During the remainder of 1987 the 

 water level continued to decrease and by the end of 1987 the water 

 volume was down 20 percent from full supply volume, the lowest 

 volume since 1982. As expected, there was a modest increasing 

 trend for several analytes (TDS, sulphate, and conductivity). 

 Figure 10 illustrates how the total dissolved solids concentration 

 changes inversely with reservoir volume. If the histbrical trend 

 continues and there is no significant runoff in 1988, the water 

 quality of the reservoir will be lower during 1988. 



COOKSON RESERVOIR - POPLAR RIVER POWER STATION 

 Water Volume and T.O.S. (mg/L) 



^.S.L. /^o/umej 



' I I I I I I 1 1 I I I I I I I I ) I 1 1 1 1 1 1 II I I I I I I I < I I 1 1 I I I I I I I 



Jon 1982 Jon 1983 Jon 1984 Jan 1985 



YEARS 



Jon 1986 



Jon 1987 



Figure 10. Variation in TDS Concentrations with Reservoir Volume 



