record) has been plotted. (Wenatchee was 

 selected as the air temperature in Wenat- 

 chee is representative of the Columbia 

 Basin. ) Note the similarity between the air 

 and water temperature patterns. Air tem- 

 peratures range from a low of 26° F. in 

 January to a high of 7^+° F- in July for a 

 range of U8' F. , water temperature range is 

 28° F. The rate of rise and fall of monthly 

 air temperatures is about twice that of the 

 water temperatures. Water temperature 

 changes Isig air temperature changes by about 

 one month. This is due to the high heat 

 capacity of the water and the 750 miles of 

 river lying above Rock Island. 



Figure 30 illustrates the relative 

 water temperatures in the Columbia River 

 from Grand Coulee Dam to Cathlamet during a 

 period in September 195^4- when tributary 

 water temperatures had been taken, it also 

 shows temperatures in December of 195^*^ for 

 purposes of comparison (no tributary tem- 

 peratures ) . In September, the water left 

 Coulee Dam with a temperature of 60.6° F. 

 Flowing downstream, the temperature gradu- 

 ally rose to a high of 6^4-. 4° F. at Bonne- 

 ville and then gradually declined to 63.9° 

 F. at Cathlamet. Tributary streams on the 

 east side of the mountains that flow throiigh 



areas of irrigated farming, or areas where 

 solar radiation is at a maximum, were wanner 

 than the Columbia. (Okanogan, Chelan, Crab 

 Creek, Yeikima, Snake, Walla Walla, Umatilla 

 and John Day Rivers.) Tributary streams west 

 of the mountains and those on the eastern 

 slope receiving a minimum of solar radiation 

 were cooler. (Nespelem, Entiat, Wenatchee, 

 Deschutes, Klickitat, Hood, White Salmon, 

 Wind, Lewis, Kalama and Cowlitz Rivers.) The 

 Methow and Willamette Rivers temperatures 

 were about the same as the Columbia. In 

 December, the water left Grand Coulee Reser- 

 voir at a temperature of W F. , declining 

 gradually to U3° at Pasco. Between Pasco 

 and Utaatilla, the temperature fell 2° F. 

 because of the colder Snake River inflow. A 

 low temperature of kO' F. was observed at 

 Bonneville, with a gradual rise down river 

 to 4l.5°F. , at Cathlamet, illustrating the 

 wanner winter air temperature effect west of 

 the Cascades. 



Yakima and Wenatchee Rivers and 

 Columbia Basin irrigation temperatures 



Water temperature data at selected 

 points along the stream are available from 

 only the Yakima and Wenatchee Rivers (other 

 than the Columbia). Figure 3I is a plot of 



FIG. 31 



?1 



