130 



In an analysis of this chart there are a number of factors 

 to consider, the principal ones probably being climate and soil. 

 Climate regulates consumptive use and length of growing season. 

 The fineness of the soil determines the amount and limiting 

 height of water held by capillarity above the water table and 

 the probable depths to which saltgrass roots extend for moisture. 

 As these investigations were conducted under conditions varying 

 as to length of growing season and soil, the charts for each sta- 

 tion would not be expected to show the same relation. However, 

 in most cases they show the same general slope. 



Where data are available, consumptive use is plotted for 

 a 12-month period, although there is considerable variation as 

 to the time each period begins. Thus the Owens Valley data begin 

 in January and end in December; Santa Ana data are for May to 

 April; Los Griegos from October to September; and Escalante 

 Valley, Utah, from May to October. These differences are deemed 

 unimportant, however, as long as a complete cycle of seasons is 

 included. In his report of the Owens Valley study, Lee (16, 17) 

 divided the year into summer and winter seasons and plotted the 

 consumptive use-depth relation for each period separately. With- 

 out discussing the benefits of such division, it is apparent that 

 the two methods disagree when used to indicate the limiting depth 

 to which saltgrass roots appear to function. This has been given 

 for Owens Valley as 7.7 feet for the period April 1 to September 

 30, and 7-0 feet from October 1 to March 31. If consumptive-use 

 data had been plotted for the entire year, however, the limiting 

 depth would appear to be somewhat less. 



In comparison, the limiting depth for a 12-month period at 

 Santa Ana appears to be 5.3 feet for fine sandy loam soil, and 

 3.8 feet at Los Griegos for clay loam soil. Consumptive -use data 

 for Owens Valley and Santa Ana plot as parallel lines, yet the 

 Owens Valley curve represents approximately 10 inches greater use 

 of water for any given depth to water table. 



