THE DUTY OF WATER IN ARIZONA. 



253 



So if the rainfall be but 2.4, or 6 inches, and we 

 apply the full practical duty of water thereto, in addi- 

 tion, is it not just so much injurious water that had 

 much better remain in our reservoir, or be used upon 

 other lands'? 



Suppose we should get 6 inches of rainfall upon the 

 40 million acres which he estimates we can irrigate, 

 it will be equal to 18 inches on IS 1 ^ million acres. 

 Why cannot we utilize this and thus extend the area 

 to be irrigated? I know we practically get the bene- 

 fit of the 7 inch rainfall in this valley, and why not 

 in other places? 



POSSIBLE AREA CAPABLE OF IRRIGATION. 



And now I will consider the vital question with 

 Major Powell the area which can be irrigated. His 

 estimate is 40 million acres. I have already shown 

 that this may be increased to 53*3 million acres, 

 leaving his conclusion about the possible and prac- 

 tical duty of water as he makes them, without elimin- 

 ating his errors. Now, consider that the absolute duty 

 of water according to his theory is 1.77 acre inches, 

 instead of 18 acre inches, that the evaporation and 

 waste is but 6 acre inches applying the water under 

 economic conditions, as he claims, and we have the 

 practical duty of 7.77 acre inches, instead of 24 acre 

 inches, a little less than one-third after eliminating 

 his errors, and we may irrigate three times o3 l 3 

 million acres, or 160 million acres. I will not now 

 attempt to go beyond this, leaving his theory of the 

 possible catch and the practical catch, with 60 per cent, 

 slashed off from the actual runoff to stand for the 

 present. But what about your practical application, 

 says Major Powell. You have used 20.24 and even 29 

 acre inches, at least as much as I have claimed the 

 practical duty to be. Yes, I admit that, but that is 

 where the variables come in. Central Arizona is but a 

 small portion of the arid region of the United States, 

 and there is nothing else like it anywhere, and I do 

 not know of any other place where the transpiration 

 and evaporation should be as great as here. Consider 

 the altitude, 1,100 feet, the distance from the sea 

 coast, 300 miles, the extreme dryness of the atmos- 

 phere, and the depth of the soil, from 5 to 10 feet. 

 Where else are these conditions all to be found? On 

 what extent of the arid region can you produce five 

 crops of alfalfa in one season? On what extent can 



you raise more than two crops? On what extent can 

 you produce a crop of wheat or barley and then a 

 crop of corn in the same season? I have shown you 

 that we can produce one crop of alfalfa with 5 acre 

 inches of water ; that we can produce three crops 

 with 12 acre inches; that we can produce a crop of 

 wheat or barley with 14 acre inches, and a crop of 

 corn with 15 acre inches. With the exception of a 

 small proportion of the arid region, two crops of 

 alfalfa, one crop of wheat or barley, one crop of corn, 

 and one crop of any other plant is the most that 

 would be attempted, and hardly anywhere else would 

 the demand for water be so great as here. 



AVERAGE AMOUNT OF WATER REQUIRED. 



The average here would be between 12.14 and 15 

 acre inches. These added together make 41, and % of 

 41 is 13.66 acre inches, and we could irrigate 110 million 

 acres, if the whole arid region required as much as 

 we do. I am led to believe that if Major Powell had 

 not fallen into the grave errors, to which I have 

 called attention, he would have found that the amount 

 of land possible to irrigate in the arid region would 

 not fall much, if any, short of the 160 million acres. 

 It is intended that we, the people, shall be benefited 

 by the expenditure of the large amount of money an- 

 nually devoted to paying the expenses of that par- 

 ticular branch of our political economy that is di- 

 rected by the genius of Major Powell, and it may be 

 well for us to take heed and abide by his statistics 

 and theories. But when we detect him in commit- 

 ting errors, even though it may be only the trifle, 

 1,830 tons in the weight of, or 16*4 acre inches in the 

 depth of the absolute duty of water for one acre, is 

 it not natural that we should have some grave doubts 

 about the correctness of his statement in general? 



I have considered the position he occupies, and the 

 high reputation he bears in his profession, and I 

 have tried to reconcile his statements and theories, 

 and the result is here given. If any person can 

 throw any more light on the subject, I shall be glad, 

 for I am in search of light on the subject of irriga- 

 tion, and the amount of water that various plants 

 will transpire while growing, and how much will 

 evaporate in the same time from different soils under 

 different climatic conditions. 



