CONDUCTIVITY 



micromhos of 25* C 



FIG. 11 



metric indicators and also with a portable, 

 battery operated, glass electrode pH meter. 

 Tbe glass electrode method iisually gave pH 

 veLLues from 0-0.4 units higher than those 

 given by the colorlmetric method. Colori- 

 metric values would differ by 0-0.2 units, 

 depending upon the indicator used. 



All of these pH values are at best, 

 approximations, for the following reasons: 



1. Colorlmetric methods are subject 

 to error frc«n color perception of 

 the observer, deterioration of the 

 standards or the indicator sind firm 

 pH alterations by the indicator In 

 poorly buffered samples of water 

 (19). 



2. Electrcmetric methods are affected 

 by temperature of the samples. As 

 the sample warms, the pH will rise 

 because of an increase in ioniza- 

 tion in the sample and because of 

 the nature of the electrodes them- 

 selves. This change in tempera- 

 ture was compensated for with the 

 meters used when the water tem- 

 perature was well above 10° C. 

 When the water temperatures were 



around 10° C. or lower the pH 

 readings would be low. Thus, if 

 a sample wanned from 10° C. to 

 20° C. from the time of sampling 

 to the time of pH measurement, the 

 pH read would be above that actu- 

 sLLly existing in the river. Elec- 

 trometric pH values should be re- 

 corded with the sample temperature 

 at the time of pH measurement. 



PRESENT STATUS OF WATER QUALITY 



- COLUMBIA RIVER BASIN 



Reservoirs 



Insufficient data were obtained from 

 reservoirs within the Colimibia River Basin 

 to enable the presentation of noimal water 

 quality data thereon. From a study of the 

 data obtained by the University and reser- 

 voir water quality data from other sources, 

 there appears to be no significant effect 

 of existing reservoirs on downstream water 

 quality other than by a change in tempera- 

 ture and a levelling out of the constituent 

 values. This has not always been true. 

 Following the construction of Merwln Dam 



33 



