70 



SUPPORTING TANK DATA 



The general data secured by measurement of consumptive use 

 of water by stream-bottom vegetation led to further study of sim- 

 ilar vegetation grown in tanks. Two tanks, each about 2 feet in 

 diameter by 3 feet deep, were set in the ground near the upper 

 control where surrounding vegetation was nearly representative of 

 that in the entire area. Tank A was planted to tules and reeds, 

 while small willow shoots were set in tank B. Measurements of 

 use of water by the tank growth were carried on from October 1929 

 to June 1930 at this location. In June, tank B was moved 20 miles 

 to Ontario and fitted with a sensitive automatic device for sup- 

 plying water to the tank as it was consumed by the vegetation, and 

 with a recorder for obtaining continuous hourly records of these 

 losses. The willow shoots in tank B were not representative of 

 normal willow growth because of their small size. In fact, they 

 failed to survive the winter months and were gradully supplanted 

 by swamp grass and weeds. Water was maintained at about 3 inches 

 above the ground surface. The monthly use by vegetation in the 

 tanks is shown in Table 15. 



TABLE 15 



CONSUMPTIVE USE OF WATER BY SWAMP VEGETATION IN TANKS AT 

 TEMESGAL CREEK AND AT ONTARIO, CALIF., 1929-30 



Water used 



Tank A 



Tules 

 Inches 



Tank B 



Willow shoots 



swamp gra s s , 



and weeds 



Inches 



17 Not applicable to large areas without adjustment, 



