WATER LOSSES FROM WET AREAS 



87 



TABLE 30 



SUMMARY BY MONTHS OF MEAN TEMPERATURES, WIND MOVEMENT, EVAPORATION, 



AND CONSUMPTIVE USE OF WATER FROM TULE TANKS NOS. 1, 2, AND 3, AND 



USE OF WATER FROM TULE TANK NO. 3, EXPRESSED IN PER CENT 



OF EVAPORATION AT VICTORVILLE STATION' 



' This table is based on all data from February 1, 1931, to February 28, 1933. 

 ' Per cent based on totals per year. 



As tule Tank No. 3 replicated SAvamp conditions, the mean annual 

 use of water from this tank was employed in determining a factor to 

 be applied in calculating- swamp use from an evaporation pan record. 

 As the mean annual evaporation from the standard Weather Bureau 

 pan was 82.46 inches and the mean annual use of water from tule Tank 

 Xo. 3 was 78.45 acre-inches per acre, the use of Avater from the tule 

 swamp area Avould be 95 per cent of the eA^aporation from the Weather 

 Bureau pan. 



The evaporation from a lake surface may be estimated as 0.7 of 

 the mea.sured loss from a standard Weather Bureau pan. The mean 

 annual evaporation from a lake surface is, therefore, indicated to be 

 58 inches. The mean annual loss from tule Tank No. 3, Avhich replicated 

 natural conditions, Avas 78.45 inches. This indicates that the annual 

 use by tules would be 20 inches more than the loss from a lake surface. 

 Tliis is probably a maximum differential and Avould be expected in a 

 swamp area completely coA^ered Avith tules groAving in water. 



It may be seen from Plate XI that a considerable portion of the 

 moist area aboA'e the Narrows is coA'ered Avith a scattered groAvth of 

 cottonwoods interspersed with patches of open sandy areas. The dense 

 tule groAvths are restricted principally to sections along the main chan- 

 nel of the riA'er and in the swampy areas such as the one on which the 

 station Avas located. The mean annual consum]:)tiA'e use for the entire 

 moist area Avould undoubtedly be appreciably less than the value of 

 78 acre-inches per acre per year determined for the tule sAvamp areas. 



If the period from ]May to October, inclusive, be considered, and 

 a comparison made for that interval, it is found that tlie use of Avater 

 by the tules Avas 61.93 inches, and the estimated evaporation from a 

 lake surface, 40 inches. The difference is 22 inches, and for this period, 

 the loss of water from a tule sAvani]) area would be 155 per cent of the 

 loss from a free Avater lake surface. 



