60 



Tank 3 



^^^Top of bonk ' 



V 



^_ _-y 



'»-»■- 



§ 



Thermometer 

 Supply tanks □ 



Anemometer Evaporation 

 ^ pan 



Rain gage 



Q 



Supply we 



I'O 



Sfrefc 



Edge of swomp \ \^"PP'y ^^"^ 



Q 



Ground water 

 ^rs. well 



Tank I 



61-0"- 



FIGURE 7. — Plan of Victorville station. 



The highest consumptive use occurred during July, averag- 

 ing 14.13 inches in depth for the 6-foot tank protected by sur- 

 rounding swamp vegetation as compared with 63-38 inches by the 

 exposed 2-foot tank. No material difference in the use of water 

 was found between tanks of different size in the swamp. The 

 larger tank is preferred as providing greater opportunity for 

 root expansion and maintenance of soil fertility. A condensed 

 summary of evaporation, consumptive use of water, and meteorolog- 

 ical data for the 2-year period is presented in Table 11. 



For this period the average annual depth of water used by 

 tules in the 6-foot tank in the swamp was 78.45 inches as against 

 272.24 inches by the exposed tank, clearly demonstrating the ef- 

 fect of unnatural exposure upon consumptive use. The second ob- 

 jective of the investigation was to determine the relation of 

 consumptive use to evaporation from a Weather Bureau pan. During 

 the 2 years of study the average annual consumptive use was 78.45 

 inches, or 95 per cent of the evaporation. This relation is not 

 constant but varies throughout the year from a maximum of 122 per 

 cent in September to a minimum of 57 per cent in March. 



The conditions of evaporation from a Weather Bureau pan 

 and from a lake or reservoir are so dissimilar that a reduction 



