82 THE FUTURE OF ARID LANDS 
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| 
| Average annual potential evapotranspiration in Utah, 
| Colorado, Arizona and New Mexico, in inches. 
Light figures, potential evapotranspiration computed by T-E method 
Bold faced figures, consumptive use, from various sources 
Figure 4. Distribution of average annual potential evapotranspira- 
tion in Utah, Colorado, Arizona, and New Mexico. 
information on the basis of these known limitations and to read- 
just their estimates of irrigation requirements and of the water 
resources of the arid areas. 
One of the objects of this paper has been to show the usefulness 
of the concept of potential evapotranspiration in arid and semi- 
