YAKIMA RIVER IRRIGATION AMD 

 POLLUTIONAL EFFECTS 



The Yakima River is the most highly 

 developed and most highly utilized water 

 source in the Columbia River Basin. Its 

 waters Irrigate 425,000 acres and receive 

 the treated waste discharges frcm some 

 76,000 persons and from industries (mostly 

 late summer food processing) having an 

 oxygen demand population equivalent of 

 138,000 persons. Table 27 lists the prin- 

 cipal irrigation projects (see map of area) 

 and diverted irrigation water for the irri- 

 gation year of 195'*« The average diverted 

 water per acre was k.kQ acre-feet for the 

 season. If this quantity of water were 

 applied uniformly to the 425,000 acres 

 irrigated in the valley, an average total 

 river flow of 5,820 c.f.s. would be required 

 to supply this diversion. 



In the peak irrigation months of 

 Jxily and August, an average of O.92I acre- 

 feet per acre per month of water was 

 applied to the land which would require a 

 total river flow of 6,580 c.f.s. Consider- 

 ing JMly and August of 195** to be average 

 Irrigation months tind with a total average 

 Yakima River available flow of 5,100 c.f.s. 

 in July and August, it Is apparent that 

 the water diverted for irrigation exceeds 

 the river flow by about 1,400 c.f.s. This 

 extra water used ccmes frcm irrigation 

 return flows upstream fron the point of 

 diversion. Thus, the entire river flow is 

 utilized for irrigation with seme of the 

 water being passed over the land more than 

 once. 



During the late summer, there are 

 times when nearly the entire river flow 

 is diverted near Parker (between Mapato 



YAKIMA RIVER BASIN 

 AREA MAP 



f.«r. I. Mil.. 



-! — I — n — k 



FIG. 60 



87 



