An interesting fact determined from studies at the 

 Bakersfield station was that cleanliness, or presence of algae 

 growth, had little effect upon evaporation rates from evaporation 

 pans. During an l8-month period starting in January 1959, three 

 pans were maintained in the same environment and were treated in 

 an identical manner, except that algae was permitted to grow in 

 one pan while the other two were cleaned frequently. The dif- 

 ference of evaporation vms small, with only 3 percent greater 

 evaporation in the pan where algae was allowed to grow. 



In an evaporation investigation carried on by A, A. Youn 

 in Southern California during the period from 1935 to 1939, inclu- 

 sive, a study was conducted to determine the effect of pan color 

 upon evaporation. He found differences varying from approximately 

 17 percent less to 7 percent more than from a standard U. S, Weathe 

 Bureau pan. It is of Interest to note that evaporation from a 

 dark green colored pan was 2.5 percent greater than that from the 

 standard U, S, Weather Bureau pan. The presence and growth of 

 algae appear to give similar results. 



The difference in evaporation between black and white 

 atmometers, as shown in Table 2, appears to be affected less by 

 environmental conditions than are pans. This indicates a differenc 

 in response bet^^reen pans and atmometers to various climatic condi- 

 tions. This will be discussed further 3n Chapter IV. 



Monthly evaporation data from pans and atmometers for 

 each year and for each station are set forth in Tables A-2 and 

 A-3, respectively, of Appendix A, The data are segregated by area 

 and by environment. 



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