fllvER MILES FROM MOUTH Of LEWtS RtVEH 



AVERAGE WATER QUALITY IN LEWIS RIVER 

 SUMMER 1954 - 55 



COLUMBIA RIVER SURVEY DATA 



RIVER MILES FROM MOUTH OF lEwiS RIVER 



AVERAGE WATER QUALITY IN LEWIS RIVER 



SUMMER 1954-55 



COLUMBIA RIVER SURVEY DATA 



FIG. 22 



Yakima River, the rise in constituents 

 during the suramer is more a function of the 

 decrease in flow than it is a function of 

 increased irrigation. 



Figures l8 and 19 illustrate the pro- 

 gressive water quality change in the Yakima 

 River during the summer as it flows from 

 Thorp (above the irrigated area and center 

 of population) to Enterprise, near the 

 river mouth. A very large rise in all con- 

 stituents, except for ammonia, is shown. 

 The most pronounced increase occurs after 

 the river enters the lower valley and 

 passes the bulk of the irrigated acreage . 



Snake River: I'^axinmm and mininrum constitu- 

 ent values in the Snake River are closely- 

 related to the rate of river disciiarge, as 

 shOT-m in figure 20. Color and turbidity are 

 greatest with h igh d ischarge in Kay and the 

 other constituents are greatest during low 

 discharge in the autvunn. At its confluence 

 with the Colu3T±iia River below Pasco, the 

 Snake River constituent values are nuch 

 higher than those in the Columbia River. 

 In the case of sulfate, they are several 

 hundred percent greater. 



FIG. 23 



Wenatchee River: This river is relatively 

 low in dissolved substances as shown in 

 figure 21. Total solids are markedly 

 affected by the higher turbidities during 

 the period of the spring runoff. Maximum 

 constituent values and conductivity were 

 observed in the winter and early spring 

 when stream flows were low. This river 

 system will be discussed in detail in a 

 subsequent report. 



Lewis River: The Yale and Merwin Dams are 

 high dams used for power production. These 

 are the only significant man-made changes 

 in the Lewis River Basin (other than log- 

 ging) that might affect water quality. 

 Station 5 represents water quality as it 

 enters the upper reservoir; station h, 

 water quality between the two reservoirs; 

 and station 3j water quality below the 

 reservoirs. Values plotted in figures 22- 

 23 are for the summer period only. All 

 values but hardness (and its constituents, 

 calcium and magnesium) are lower below the 

 dams than above. This can be explained by 

 the fact that the reservoirs are large and 

 that portion of the water they are spilling 



39 



