118 



DIVISION OF WATER RESOURCES 



pan sunk in the stream channel and completely surrounded by the 

 stream, and a recorder on a ground water pit about 10 feet away from 

 the stream. 



Readings were taken at all installations throughout this period 

 each day near sunrise, near sunset, and at various other times. Rela- 

 tive humidity was determined with a sling-psychrometer near the mouth 

 of the canyon and at various locations in the canyon. The maximum 

 and minimum discharges at the middle and the lower controls also were 

 carefully checked each morning and evening. 



PLATE XXX 



September 1932 



UJ 



COMPARISON OF LOSS OF Vi'ATER FROM EVAPORIMETER AND AIR 



TEMPERATURE NEAR MOUTH OF COLDWATER CANYON, 



SEPTEMBER 7-15, 1932. 



Plate XXX shows the comparison, during the period, of the air 

 temperature near the mouth of the canyon with the evaporation from 

 the evaporimeter at the same location. Note that insolation is the 

 primary causative factor controlling the loss from the evaporimeter, 

 since it is very nearly in phase with the radiant energy cycle and 

 reaches a maximum each day just about noon. The air temperature 

 lags behind and does not reach a maximum generally until around 

 2 p.m. 



The daily evaporation from the evaporimeter compared with the 

 daily loss from the atmometers, both in the canyon and at the mouth 

 of the canj^on, is given in Table 44 together with the daily loss between 

 the middle and the lower controls. 



The record of the fluctuations during this period in the ground 

 water pit has alreadj^ been referred to and is shown on Plate XXVI. 

 The evaporation from the evaporation pan also has been discussed and 

 the dailj^ values given in Table 33. 



