108 



closely with consumptive use by tules at Isleta, N. Mex. , but 

 exceeds amounts at other tule stations where measurements were 

 obtained in swamp areas as distinguished from exposed tanks. 



ESCALAMTE VALLEY, UTAH 



The general method of estimating consumptive use by native 

 vegetation through attention to ground-water fluctuations has 

 been previously described. White (38), using the same method in 

 the Escalante Valley, Utah, as described by Smith in Arizona (see 

 page 18), shows that ground-water fluctuations respond to the 

 vegetal demand for moisture with declining water tables during 

 hours of sunlight and rising water tables during the night. 



Observations were made in 1926 and 1927 to determine con- 

 sumptive use by various species of native vegetation and to esti- 

 mate the water resources of the valley. This is a desert region 

 yet one in which a considerable area of native growth subsists 

 upon ground water close to the surface. Vegetation consisted 

 principally of saltgrass, greasewood, sagebrush, rabbitbrush, 

 shadscale, pickleweed, and willow. 



To determine the effect of consumptive use by these plants, 

 wells sunk in areas of each predominant species were equipped with 

 water-stage recorders. With this equipment, diurnal fluctuations 

 of the water table for each area were determined. The extent of 

 the fluctuations varied, not only with soil type but also, and 

 what is of greater importance, with the age, vigor, density, and 

 type of plant growth. The maximum daily draw-down observed ranged 

 from 1 1/2 inches for an area of greasewood to 4 1/4 inches in a 

 field of marsh grasses. Samples of recorder charts for several 

 vegetative species are shown in Figure 14. 



Ground-water fluctuations as described can only be trans- 

 lated into depths of consumptive use through determination of the 

 specific yield of the soil on which the vegetation grows. Obvi- 

 ously for large areas this is difficult because of ever-changing 

 soil conditions throughout the area. To obtain values of specific 



