are evened out or are delayed when there is 

 a large upstream Impoundment. Color and 

 turbidity may be greatest during periods of 

 high dischaz^. Their compeirlson by weighted 

 averages is questionable. 



In the Columbia River Basin, Van 

 Winkle's data are compared with contempo- 

 rary data in tables 15 to 23 and figures 

 U3 to 59 for the following locations: 



Columbia River at Northport (Inter- 

 national Boundary) 



Columbia River at Pasco 



Colxmibia River at Cascade Lock and 

 Maryhill 



Wenatchee River at Cashmere 



Snake River at Burbank, Central 

 Ferry, and Clarkston 



Yakima River at Cle ELum 



Yakima River at Prosser and Kiona 



Deschutes River at Moody 



Okanogan River at Okanogan and near 

 the mouth 



These tables and figures show the actual 

 observed constituents. To properly evaluate 

 the change in constituents, the reader must 

 also compare the difference in stream dis- 

 charge for that month (a higher discharge 

 results in more dilution of constituents ) . 



Table 2k is a ccmpilation of the 

 yeeurly weighted averages for seven of these 

 stations. Average monthly values are 

 weighted according to flow by multiplying 

 the average monthly flow by the average 

 monthly constituent, summing them for the 

 year, and dividing the sum by the total of 

 the monthly flows. Table 25 shows the 

 approximate changes in population, Indus- 

 try, and irrigated acreage from I9IO to 

 1950 and table 26 gives the changes in 

 river constituents on a tonnage beisis. 

 These tables and figures sa« described 

 below: 



Colimbla River at Northport (Inter - 

 national Boundary), Figures ^3 and kh , 

 Table 15 : 



The Columbia River and tributaries 

 above the International Boundary pass 

 through a series of large lakes or impound- 

 ments. These impoundments tend to even out 

 the river flow and the change In water 



quality that cosaes with changes in river 

 flow, 5,039,000 acre-feet of impounded water 

 have been Eidded to this stream section since 

 1910. Decreases in dissolved constituents 

 will be reflected in downstream stations 

 three months past the period of high runoff 

 (figs. 10 and 11, reference 50) wherejis in 

 a stream without impoundments, these changes 

 will be observed coincidental with the change 

 in flow. Between I910 and 195Ci there was a 

 h6 percent increase in watershed population, 

 a 32 percent increase in irrigated acreage 

 and an industrial waste addition to the rlAier 

 equivalent to an estimated population of 

 513^000 persons on an oxygen demand basis. 

 The average river discharge during these two 

 periods of ccmparison differed by only k 

 percent. 



Figures k^ and hh show an increase in 

 all constituents excepting for sodium plus 

 potassiimi and silica. An increase in all 

 mineral constituents could be expected be- 

 cause of an increase in waste discharge to 

 the river, denudation of forest cover frcm 

 logging and because of an increase in irri- 

 gation. Between I9IO and 1952, the river 

 constituents increased by the following per- 

 centages: Alkalinity - 5; hardness - 1^; 

 dissolved solids - 6; sulfate - 19; calcium 

 plus magnesium - Ik; chloride - 125; and 

 nitrates - 220. Iron showed no change while 

 sodium plus poteisslum decreased ^1 percent 

 and silica 20 percent. The 300 percent in- 

 crease in nitrates and 200 percent in chlo- 

 rides can be expected from the Increased 

 discharge of organic matter and municipal 

 wastes to the river. No plausible explana- 

 tion can be advanced as to why silica and 

 sodium plus potassium did not also Increase 

 during this period of time. 



Columbia River at Paaco , 

 Figures k'y and kb, Table I6 ; 



The data shown herein for 19514-56 

 were collected by the University and do not 

 represent as accurate a representation of 

 the water constituents as do those collected 

 by the U. S. Geological Survey since sample 

 collection was less frequent. There are no 

 flow data for the I910 sampling period. 

 Since these two sets of data are not direct- 

 ly comparable, they can be examined only in 

 a very general sense. Sodium plus potassium 

 valxies have shown an apparent decrease (as 

 at Northport) and calcium plus magnesium and 

 sxilfates have shown little change. The 



68 



