WATER LO^iRES FRf^r WET AREAS 



83 



1931 the highest use from Tank No. 2 occurred in May, before the 

 tank was entirely surrounded by swamp growth, and amounted to 16.03 

 acre-inches per acre, while the highest use for Tank No. 1 occurred in 

 July, and amounted to 55.83 acre-inches per acre. The use in July 

 from Tank No. 2 was 14.37 acre-inches per acre, which is approximately 

 one-fourth of the use from Tank No. 1 for that month. This difference 

 must be due to the relative exposures of the two tanks, since the density 

 of stalks was not materially different. When the tules were set out in 

 1931 the plants in Tank No. 2 started to grow and use water earlier 

 than the plants in Tank No. 1, because they were warmed by the rising 

 water that flowed around the tanks in the swamp. A flood in May, 

 1932, damaged Tank No. 2 and the connected supply tank, so that the 

 record from this tank is incomplete for 1932. The record for 1931, 

 however, supplied the data necessary for the principal objective — 

 demonstration of the effect of exposure on the use of water from 2-foot 

 tanks. This is shown graphically in Plate XVII. A comparison on a 

 mean monthlv basis for the entire period of record is shown in 

 Plate XVIII. * 



PLATE XVIII 



Jan. 



\ Indicating excessive use 

 44*^ of tvafer, due to plants 

 y//y_ \in no I Tank being _ 

 away from natural 

 environmenf. 



Nov. Dec. 



MEAN MONTHLY EVAPORATION AND USE OF WATER FROM TANKS NO. 



NO. 2, AND NO. 3. 



1, 



A complete record was obtained from tule Tank No. 3 during both 

 the 1931 and 1932 seasons. This tank was 6 feet in diameter and had 

 a normal swamp expo.sure with a growth of tules completely surround- 

 ing the tank, so that there was a replication of natural conditions. The 

 highest monthly use of water from this tank occurred during July in 

 each year, amounting to 14.65 acre-inches per acre in July, 1931, and 

 13.61 acre-inches per acre in Juh% 1932. The mean annual use of 

 water from this tank based on the 25-month period from February, 

 1931, to February, 1933, is 78.45 acre-inches per acre. This value was 



