142 percent) are due to photosynthetic 

 activity of the plankton. Carbonate alka- 

 linity was observed from July through Decem- 

 ber with the maximum August value of 56 

 mg/1 as CaC03 occurring during the period 

 of peak irrigation return flow. Soluble 

 mineral matter, as indicated by the conduc- 

 tivity, calcium and magnesium, etc., was 

 greatest in the autumn and winter when the 

 reservoirs were drawn down and when the 

 river flow consisted largely of ground water. 

 High total solids, color and turbidity 

 values in February and March are not normal 

 values for these months. They were caused 

 by work on the Ice Harbor Dam, 8 miles 

 upstream from the point of sampling. 



Columbia River at Pasco 

 Table 8, Figures 11 and 12 : 



In a warm summer, the average-monthly 

 water temperatures in August and September 

 exceed 65° F. Carbonate alkalinity was 

 observed only during the month of August, a 

 period when carbonate alkalinity (C03= ) was 

 maximum in the Yakima River which discharges 

 into the Columbia River 5 miles upstream 

 from Pasco. Dissolved oxygen saturation, 

 corrected for elevation and saturation table 

 deficiencies (see discussion on reliability 

 of water quality data), is equal to or 

 greater than 100 percent saturation through- 

 out most of the year. Maximum color, tur- 

 bidity and total solids were observed in the 

 spring when the snow-melt at lower elevation 

 tions was proceeding most rapidly. Ionized 

 dissolved substances, as measured by conduc- 

 tivity, are least during June, the period 

 of maximum runoff. 



Yakima River at Enterprise 



The Yakima River flow is regulated 

 for irrigation excepting during the spring 

 runoff. Marked changes in water quality 

 occur as the river passes through the irri- 

 gated areas and receives large quantities 

 of return flow. During the summer, the 

 majority of water in the lower river is com- 

 posed of return flows. In July and August, 

 water temperatures at Richland have exceeded 

 80° F. At Thorp, the Yakima River is a 

 typical cool, clean, slightly alkaline, low- 

 dissolved solids stream while at Enterprise, 

 153 river miles downstream, the river is 



warm, alkaline 2ind relatively high in dis- 

 solved organic and inorganic solids. Table 

 26 is a comparison of average values for 

 typical constituents at Thorp and Enterprise 

 for the month of August (heavy irrigation 

 return flows). Dissolved oxygen concentra- 

 tions are high at Enterprise despite the 

 volume of organic wastes discharged into 

 the Yakima River from municipalities, indus- 

 try and from agriculture. Dissolved oxygen 

 values during the hours of darkness were 

 2-3 p. p.m. less than during daylight hours 

 but they did not drop below 6 p. p.m. at 

 Enterprise (26). 



Table 26. — Comparison 

 water quality, average 



of Yakima River 

 values for August 



Water temperatures have risen above 

 65° F. for 5- or 6-day periods during August 

 and September. However, the night tempera- 

 tures have dropped well below 65° F. on 

 these occasions. This river, even at the 

 mouth, is of high quality. The water is 

 normally clear, slightly alkaline and satu- 

 rated with oxygen. Turbidity, total solids 

 and color are high only during the period 

 of spring runoff. In contrast with the 

 Yakima and Snake Rivers, the Wenatchee River 

 has but 0.36 of the dissolved material that 

 is in the Columbia River at their point of 

 confluence (using average yearly constituent 

 values) . 



Crab Creek near Mouth 



Table 12, Figures 19 and 20 : 



The flow in Crab Creek is low and 



92 



