IN REPLY TO POWELL: HOW MUCH WATER DOES 



A CROP REQUIRE? 



BY W. C. FITZSIMMONS. 



IN the February issue of THE IRRIGATION AGE 

 Major J. W. Powell, Director of the United 

 States Geological Survey, discussed at length the 

 question of the amount of water required to produce 

 crops of various kinds. Among the statements made 

 by Major Powell in this connection are these: 

 " Cereals, such as wheat, oats, barley and corn, will 

 exhale their dry weight in water every day. 

 Two tons of hay require 200 tons of water, which is 

 about 18 acre inches. If the crop of hay on an acre 

 is two tons the acre of grass will transpire 18 acre 

 inches of water." The distinguished writer alleges 

 that these results have been reached after more than 

 a century of labor among men of science in this 

 direction. After admitting that to some extent it is 

 a question of latitude, altitude, atmospheric humidity, 

 etc., Major Powell sums up the matter thus: " In the 

 western half of the United States, the mean absolute 

 duty of water, plus the practically unavoidable evap- 

 oration, is 24 acre inches for every average acre of 

 crop. Otherwise stated, an acre of growing crop will 

 drink up by its roots and exhale by its leaves an acre of 

 water 18 inches deep during one season, and in apply- 

 ing this water under economic conditions an acre of 

 water 6 inches deep must be wasted by evaporation. 

 The absolute duty of water is 18 inches; the possible 

 duty, 20 inches; the practical duty, 24 inches." 



All this, briefly stated, means that an average crop 

 (of wheat for example) absolutely requires for its 

 successful growth and maturity at least 18 acre 

 inches of water, none of which can be spared by drain- 

 age, evaporation or otherwise. That this amount of 

 water must be drawn from the soil by the roots of the 

 plant and utilized in its growth by the processes of 

 nature. But the inevitable waste by evaporation and 

 otherwise requires a greater rainfall than 18 inches, 

 and the minimum is fixed by Major Powell at 24 

 inches, without which an average crop is impossible. 

 It is interesting to note in this connection that it has 

 required a hundred years of scientific research to 

 determine this point. Had it not cost so great labor 

 and pains to establish in the scientific mind this 

 ponderous theory there might be some question in the 

 mind of the average layman regarding its truth. The 

 writer hereof has not spent a hundred years investi- 

 gating this important subject, nor does he make pre- 

 tense of being what is generally understood by the 

 gentlemen themselves when they speak of "scientists." 

 But he believes he has a somewhat firm grip on a 



few facts, some of which may be pertinent to this 

 occasion. 



Practically, and in a nutshell then, Major Powell 

 says it requires 24 inches of rainfall to produce an 

 average crop. Let us see: For thirty years Califor- 

 nia has been among the leading wheat growing States 

 of the Union. Some seasons she has led in the 

 amount produced and has always stood near the head 

 of the list. The wheat crop has never failed in that 

 State, and yet, broadly speaking, there is scarcely a 

 wheat field in California, and never has been, whereon 

 24 inches of rain has fallen in one year. But asser- 

 tion alone proves nothing ; and, unlike Major Powell, 

 it is here proposed to array incontestable facts and 

 figures from the highest authorities to support the 

 assertion above made. 



From 121 different localities in California, in or 

 near which wheat is grown on a large scale every 

 year, the writer has compiled the following data from 

 the records of the Weather Service in San Francisco, 

 and they cover periods ranging from two to forty 

 years: Average annual rainfall for the 121 stations, 

 15.5 inches. Minimum in any locality known to the 

 writer to be a successful wheat-producing district, 

 (Tulare), seven inches; maximum, (Auburn), 32.55 

 inches. Of the 121 stations, only eleven show a rain- 

 fall greater than 22 inches, and nearly all- of them are 

 in parts of the State where comparatively little wheat 

 is grown. 



To show that California's wheat crop is at least an 

 average one, we may cite the fact derived from fig- 

 ures published by the United States Department of 

 Agriculture, showing that for the past fifteen years 

 the average yield of wheat by the whole country has 

 been about 12 bushels, while that of California for 

 1893 was 13.3 bushels. The average of the whole 

 country for the last crop was 11.2 bushels per acre, 

 while that of some of the principal wheat-growing 

 States east of the Rocky mountains was as follows: 

 Michigan, 13 bushels; Ohio, 14.5; Illinois, 11.5; South 

 Dakota, 9; Missouri, 9.5; Indiana, 14; Kansas, 8.4; 

 Tennessee, 9; Minnesota, 9.6. It will thus be seen 

 that the average yield of California, which was not an 

 unusual one, was nearly 20 per cent, more than the 

 average for the country, and notably greater than in 

 Illinois, Dakota, Missouri, Michigan and Minnesota, 

 where a much greater annual rainfall is found than in 

 California. It may not be out of place to state here 

 that the value of this practical test, showing that 



