WATER LOSSES FROM WET AREAS 



101 



controls, if the same rate were maintained, would be 0.013 acre-inch 

 per day. Between these controls the average measured loss of water 

 per day durino; this period was 1.06 acre-inches. Therefore the evapo- 

 ration would be only 1.2 per cent of the total measured loss. These 

 values are shown in Table 33 together with the daily comparisons 

 during the period. 



TABLE 33 



COMPARISON OF ESTIMATED LOSS BY EVAPORATION FROM STREAM AND TOTAL 

 LOSS BETWEEN MIDDLE AND LOWER CONTROLS IN COLDWATER CANYON 



September 8-14, 1932 



Date 



1932— 

 September 8 

 September 9 

 September 10 

 September 11, 

 September 12 

 September 13 

 September 14 



Averages 



Depth of 



evaporation 



from tank 



2 feet in 



diameter 



surrounded 



by stream, 



in feet 



0.015 

 .007 

 .000 

 .007 

 .008 

 .005 

 .005 



.0076 



Estimated 



evaporation 



from stream 



in acre-inches' 



0.026 

 .012 

 .010 

 .012 

 .014 

 .009 

 .009 



.013 



Loss between 



middle and 



lower controls, 



in acre-inches 



1.44 



1.19 

 .91 

 .86 



1.01 

 .97 



1.01 



1.06 



Estimated 



evaporation 



loss expressed 



as a percentage 



of total loss 



1.8 

 1.0 

 1.1 

 1.4 

 1.4 

 .9 

 .9 



1.2 



tank. 



> Evaporation computed for a stream surface 3 feet wide by 2,080 feet long at same rate as evaporation from 2-foot 



The true rate of evaporation from the stream would no doubt be 

 less than the rate from the evaporation tank, as the average daily 

 maximum temperature for the period was 2.4 degrees higher in the 

 tank than in the stream. Air and water temperatures for this period 

 are given in Table 34. It can be seen from Plate XX, which shows a 

 typical section of the canyon, that the water surface of this stream is 



TABLE 34 



DAILY MAXIMUM AND MINIMUM TEMPERATURES IN COLDWATER CANYON OF THE 

 AIR, THE STREAM, AND THE WATER IN THE EVAPORATION PAN 



September 8-14, 1932 



Date 



1932— 



September 8 

 September 9 

 September 10 

 September 11 

 September 12 

 September 13 

 September 14 



Averages 



Temperature, in degrees Fahrenheit 



Water in stream 



Maximum 



68 

 68 

 67 

 66 

 66 

 66 

 65 



66.6 



Minimum 



62 

 64 

 60 

 58 

 58 

 58 

 00 



60.0 



Water in the 

 evaporation pan 



Maximum 



71 

 72 

 69 

 68 

 67 

 68 

 68 



69.0 



Minimum 



62 

 64 

 61 

 60 

 59 

 58 

 59 



60.4 



Air 



Maximum 



100 

 93 

 86 

 85 

 87 

 85 

 83 



88.4 



Minimum 



87 

 81 

 60 

 58 

 60 

 63 

 59 



66.9 



