OtURNAL TEMPERATURE VARIATIONS IN A COLO AND MEDIUM TEMPERATURE RIVER 



PflEPAPED FROM CHELAN PUDANOFSWS THERMOGRAPH RECORDS 



FIG. 34 



the minimum temperature Is observed about 

 the time of simrise^ 6:00 a.m., vhlle the 

 nn^yifrntm temperature is about the time of 

 sunset In this sb£ided valley, 6:00 p.m. 

 In the spring and autumn, the minimum tem- 

 perature remains at about 6:00 a.m. vhlle 

 the maximum temperature occurs about one 

 hour earlier than In the summer. A tempera- 

 ture fluctuation of 5* F. Is shown for the 

 summer and 3>3* F. for the spring and 

 autumn. 



Wenatcbee River at Monitor ; The 

 Wenatchee Is a medium temperature river, 

 originating at Lake Wenatchee on the east- 

 em slope of the Cascade Mountains and 

 flowing some 55 miles to the Columbia River. 

 It has a steep gradient for flow and pajsses 

 through areas of small forest cover. The 

 mean annueil flow Is about 2700 c.f.s. A 

 diurnal temperature variation of 9 •5° F. 

 is shown for late August and 3* F. for 

 early June. The Avigust curve is character- 

 ized by its abrupt temperature changes. 

 Indicating In this unregulated stream, a 

 direct sensitiveness to air temperature 

 changes. Sensitiveness to air temperatiire 

 Is also indicated by the minimum tempera- 

 ture being at 7:00 a.m. and the maximum at 

 5:00 p.m., about the time when the sun's 



OIURNAL TEMPERATURE VARIATIONS 

 PREPARED FROM F & M S THERMOGRAPH RECORDS 



FIG. 35 



rays reach and leave the river areas. 



Yedclma River at Richland ; This is a 

 waxm, regvilated, medium sized river, having 

 an average discharge at Klona of about 3900 

 c.f.s. Frcm the headwaters in Lake Keeche- 

 lus, it flows some 205 miles through moun- 

 tainous and farming areas to its confluence 

 with the Columbia River at Richland. IKuring 

 the late summer, nearly the entire river 

 flow at Richland consists of waim, irriga- 

 tion return flows. In figure 35 > a daily 

 temperature vsirlatlon of 7* F. is shown for 

 August and h* F. for June. An interesting 

 feature of these cxirves is the displacement 

 (from other rivers) of the times of minimum 

 and maximum daily temperatures. Minimum 

 temperature is at noon while maximum tem- 

 perature is at midnight. The river tempera- 

 ture at Richleuid then is responsive to the 

 air temperatures over the large irrigated 

 area in the lower river val 1 ey where most 

 of the return flow originates. A flow time 

 of about six hours from the center of this 

 irrigated area to Richland is indicated. 



Snake River at Ripau-ia : The Snake 

 River is a cold river In the winter and a 

 waim river in the summer. It is the prin- 

 cipal tributary of the Columbia, having a 



