124 DIVISION OF WATER RESOURCES 



No definite conclusions should be drawn at this time from the 

 results of the first year's work. However, the data presented in Table 

 46 indicate that the evaporation loss from the Los Angeles County 

 Flood Control pan is greater than that from the standard Weather 

 Bureau pan at Baldwin Park during 1932. The cause of this result 

 is not apparent at this time as Sleight * found that the loss from a 

 standard Weather Bureau pan was greater than that from his 2-foot 

 pan, but it is possible that the discrepancy is due to differences in con- 

 struction and especially to the use of a cross bar in the Los Angeles 

 pan that was not used in the Sleight type. This cross bar was intro- 

 duced to make possible measurements of depth in the center of the 

 pan. 



MISCELLANEOUS EVAPORATION RECORDS 



Evaporation stations maintained by the Bureau of Agricultural 

 Engineering at locations other than Baldwin Park have been previously 

 described in Chapters II and III. 



In addition to observations of evaporation from standard Weather 

 Bureau pans at the Santa Ana and San Bernardino stations, records 

 were obtained from circular tanks 23 inches in diameter by 32 inches 

 deep, set 30 inches in the ground. Measurements were made with a 

 hook gage in a still well to prevent inaccuracies due to surface move- 

 ment. The normal rate of evaporation from the sunken tank was more 

 uniform than that from the Weather Bureau pan as the water in the 

 tank maintained a more even temperature. The total evaporation, 

 however, was less than that from the pan. Experiments by Sleight* 

 at Denver indicate that evaporation from a similar tank 24 inches 

 in diameter by 3 feet deep, set 2.75 feet in the ground was 86.2 per 

 cent of that from an adjacent standard Weather Bureau pan for the 

 period April to November 1916. This agrees closely with the average 

 ratio of 88.8 per cent derived at Santa Ana and 86.6 per cent at San 

 Bernardino for the three-year period ending April 30, 1932. The 

 difference in depths of the tank at Denver and those in California 

 is probably of no importance, but the difference of one inch in diameter 

 may have had a slight effect on the evaporation. 



Evaporation data collected by the Bureau of Agricultural Engi- 

 neering at Santa Ana, San Bernardino, Prado, Ontario, and Victorville 

 stations are summarized in Tables 47 to 51, inclusive. 



A canvass was made for other evaporation records and these are 

 published herewith as Tables 52 to 69, inclusive, through the courtesy 

 of agencies collecting them. 



* "Evaporation from the Surfaces of Water and River-bed Materials," by R. B. 

 Sleight, Journal of Agi'icultural Research, Vol. X, No. 5, July 30, 1917. 



