increased in the future from 64.9 to 65.1° 

 F. at Monitor on the VVenatchce River; from 

 63.2 to 64.8* F. at Rock Island and from 

 66.4 to 71.4° F. at Pasco, both on the 

 Columbia River. Maximum water temperatures 

 may be somewhat less than indicated since 

 the rate of temperature increase will di- 

 minish as water temperatures approach the 

 mean air temperature. If these proposed 

 dams (or a portion of them) were to be high 

 dams with large impoundments having a high 

 depth-to-area ratio, the downstream water 

 temperatures would probably be cooled rather 

 than warmed during the summer (as is the 

 case with Lake Roosevelt and Grand Coulee 

 Dam) . 



Columbia and Wenatchee river water 

 is low in dissolved and suspended organic 

 matter. The areas where water is to be 

 impounded are also low in organic matter 

 (providing the Wenatchee Reservoir site is 

 cleared of timber). Therefore it is ex- 

 pected that decomposition in the lower res- 

 ervoir levels will be minor and that there 

 will be no appreciable change in dissolved 

 oxygen due to bacterial decomposition of 

 organic matter. Other decomposition pro- 

 ducts, such as carbon dioxide, ammonia and 

 sulfides should also be insignificant in 

 the reservoirs and downstream water. One 

 to two p. p.m. less dissolved oxygen should 

 be experienced between the Wells Dam and 

 Pasco during the late summer after the dams 

 have been built because of £Ui increase in 

 water temperature and because of reduced 

 aeration. This anticipated drop in dis- 

 solved oxygen may be more than compensated 

 for by photosynthetic activity in the new 

 reservoirs. An oxygen reduction of 2 p. p.m. 

 would still leave ample oxygen for aquatic 

 life. These predictions are made with the 

 assumption that future industrial and munic- 

 ipal waste discharges to the river will 

 have low oxygen demands. 



A slight increase in the yearly 

 weighted-average dissolved constituent 

 values should be experienced in the Colum- 

 bia River after the dams are built because 

 of the longer contact time cufforded between 

 the water and the mineral matter in the 

 river bed. This increase may be quite ap- 

 preciable soon after the water is impounded 

 because of its contact with soil that has 

 previously received a minimum of leeching 

 action from rainfall. This increase in 

 dissolved mineral matter should have no 

 harmful effect on aquatic life; it may be 



beneficial by augmenting the present food 

 supply. Water turbidity during the flood 

 season should be reduced by deposition in 

 the reservoirs. Water color may be reduced 

 through increased bleaching by the sun in 

 the new reservoirs. 



SUMMARY 



A water quality study has been made 

 in the Wenatchee River Basin and on the 

 Columbia River from Beebe (near Chelan) to 

 McNary Dam for the purpose of ascertaining 

 the effect proposed dam construction will 

 have on water quality and its relation to 

 aquatic life. Six dams are under construc- 

 tion or are proposed for construction in 

 this section of the Columbia River and its 

 tributaries. These will be low-head run- 

 of-river hydroelectric facilities. Fourteen 

 water sampling stations were established 

 in the study area. Water samples were 

 analyzed for the common constituents and 

 for other constituents which might affect 

 aquatic life. 



Water quality data were summarized 

 and documented. These data will make it 

 possible to evaluate future water quality 

 data obtained after the dams have been 

 constructed. U. S. Fish and Wildlife Ser- 

 vice and Chelan County P.U.D. thermograph 

 records of water temperature have been 

 summarized and analyzed. U. S. Geological 

 Survey quality of water data have been 

 used when applicable. A comparison was 

 made of 1910-11 water quality in the We- 

 natchee River with that observed in the 

 1954-57 period. 



The Wenatchee River and its tribu- 

 taries are cool, "clean" waters. They are 

 low in dissolved constituents and are low 

 in suspended matter except during periods 

 of high runoff. The Columbia River between 

 Beebe and Pasco usually has maximum tem- 

 peratures under 65° F. It is saturated 

 with dissolved oxygen and contains only a 

 moderate amount of dissolved and suspended 

 constituents. Below the Snake River con- 

 fluence, the Columbia River water quality 

 at McNary Dam shows a narked change from 

 that observed at Pasco. During the summer, 

 the Snake River may raise the Columbia 

 River temperature by 2.5° F. and increase 

 its dissolved constituents by 20+ percent. 

 Water quality data obtained from all 

 stations throughout the year gave no data. 



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