period. As shown in figxires ^4^7 and '*8> 

 these constituent Increases or decreases 

 show no monthly correlation with changes 

 In stream discharge or with the period of 

 Irrigation and return flows. This lack of 

 correlation can be attributed to the com- 

 plexity of water quality variables upstream 

 from Maryhlll. 



Snake River, Figures k9 and 50 » 

 Table l6 : 



The U.S.G.S. water quality data were 

 collected at Burbank near the Snake River 

 mouth for the I91O-II period. From I951 

 to 1955, the U.S.G.S. collected water qual- 

 ity data from the Snake River near Clark- 

 ston. In October of 1955 > this station 

 was moved downstream to Central Ferry 

 because the Clearwater River, tributary at 

 Clarkston, was not thoroughly mixed in the 

 Snake at the sampling station below Clark- 

 ston. The data in table I8 is for both 

 the Clarkston and Central Ferry stations 

 as Indicated in the footnote. Central 

 Ferry is 8k miles and Clarkston l40 miles 

 upstream from Burbank. Water quality 

 values at these stations are comparable 



since there are no Intervening cities or 

 industries and the Intervening tributaries 

 (Palouse and Tucaonon Rivers) have a com- 

 bined flow of only 1 percent of that in the 

 Snake River. 



Between I9IO and 1950, the Snake River 

 watershed impoundment behind dams increased 

 by U, 075, 000 acre-feet, the population in- 

 creased by 77 percent, irrigated acreage 79 

 percent and industrial wastes comparable to 

 a population of 768,000 persons on an oxygen 

 basis was added to the watershed. The Snake 

 River flow in the I9IO-II period was 31 per- 

 cent higher than in the recent period under 

 comparison. This diluting effect of higher 

 flows will be compensated for by making the 

 ccoQjarison on the basis of weighted averages 

 (table 2k). 



All constituents, excepting for color, 

 were higher in the 1952-56 analyses than in 

 the 1910-11. The most noticeable increases 

 were in the suomer and autumn irtien the irri- 

 gation return flows were greatest. Based on 

 the yearly weighted averages, the percentage 

 increase in constituents were as follows: 

 Alkalinity - 6O; hardness - 70; dissolved 



Table 18. — V^ater quality comparisons. 

 Snake River at Burbank, 1910-11 (U.S.G.C.) 

 In P. P.M. 



J»n. r»b. M»r. April Mu jima Jqly lag. 3«pt. 0«t. Her. 



D50. 



Tlaet SanplMl'i' 

 rioir X 1,000 

 Tot«l Alk.' 

 SvHItU 

 Colsr 

 T«rtldlty 

 C« ♦ Kg 

 b * I 

 Slsi. SoUda 

 Total SoUda 

 Iron Cfe) 

 Total Hardnasa' 

 Stile* 

 Htnta (103 

 Ctalerld* 



^??j:i 



Vloaa 34aq>l*d'^ 



71o» I 1,000 



Total UJc.< 



SulfaU 



Colsr 



Ca ♦ H 



U* t 



Clas. Solids 



Iron 



Total Bardms*^ 



Sillea 



Bltrtta (I*,-) 



Chloride (d-) 



Snake River at Central Ferry (near Pomeroy) 

 1955-56 (U.S.G.C.) 



Jan. 



rob. 



5 

 U7 

 88 

 28 

 18 

 32 

 22.5 

 173 



0.07 

 93 

 25 



2.5 

 10 



Har. 



7 



36 



103 



33 



8 



38.6 

 25.6 

 200 



0.01 

 111 

 25 



2.1I 



68 

 79 

 23 



25 

 29.3 



17.8 

 153 



0.12 

 85 

 21. 



2.6 



9 



_4Ertl_ 



6^ 



128 



55 



11. 



15 



20.2 



11.7 

 105 

 0.06 



57 



20 

 1.3 

 5.5 



3 



102 

 57 

 18 

 22 



20.1 



U.6 

 US 

 0.10 



58 



20 

 0.7 

 5.7 



3 



165 

 57 

 17 

 20 

 19.7 

 12.6 

 105 



0.07 

 56 

 17 



0.8 



5 



Jnly» Aug.* Sopt.' 



Oct. 



Vt 



• Data for Snaka RlTor naar Clarkaton, 1952-53. 



1 Each eanpl* reprosanta eompoalt* of one to 10 dalljr salvias. 



2 Aa p.ppiu C^X>3 



38 

 86 

 36 

 17 

 31.8 

 22.1. 

 201 

 0.02 

 92 



2b 

 2.6 



10.5 



Coapotsd froa Ca and Hg aa CaCO^. 



75 



