THE ART OF IRRIGATION. 



CHAPTER XVIII. THE AMOUNT OF WATER REQUIRED. 



(Continued) 

 BY T. S. VAN DYKE. 



WHILE the acre foot is the best way of 

 estimating the amount of water 

 used in irrigation, because it counts the 

 water actually put upon the land as shown 

 in the last chapter, there will still remain 

 a great difference in the quantity used in 

 different sections and by different irrigat- 

 ors in the same section, even side by side 

 and for the same crops. And each one 

 will be quite positive that his way is the 

 best, while many will claim that they are 

 cheated out of some water evn if they use 

 -a foot to the acre. 



The extremes of the use of water seem 

 a cubic foot a second to about eighteen 

 acres on the Bio Grande about Albu- 

 querque, embracing all the lands under 

 the old ditches for miles above that point 

 and some below, to a foot to about two 

 thousand acres at Pasadena in Southern 

 California. Pasadena has an average 

 rainfall of about eighteen inches, most of 

 which enters the ground, while on the Bio 

 Grande it is practically nothing. But this 

 does not begin to account for the difference. 

 Both these estimates are made by dividing 

 the acreage served by the amount of water 

 in the aqueducts. Both the acreage and 

 the amount of water are subject to some 

 errors from measurement, but not enough 

 to affect the result very much. And as all 

 other ditches in the land are in the same 

 condition, as far as knowing exactly the 

 amount of water or land, these are as good 

 data as can be had. 



WATEB FORTY FEET DEEP. 



The ridiculous nature of the irrigation 

 on the Bio Grande is seen in the fact that 

 a foot a second would in a year cover 

 eighteen acres about forty feet deep. But 

 counting only by the irrigating season of 

 say six months, only half that would be 

 put on. But this would be twenty feet 

 in six months, or forty inches in depth per 

 month. Allowing as much as ten per cent. 



of waste at the lower end of a tract to in- 

 sure good wetting of that part, and we 

 still have thirty-six inches, which would 

 be a larger rainfall than any part of the 

 United States has during the whole grow- 

 ing season, and would be equal in effect to 

 twice that amount of rain as it usually 

 comes. This is three acre feet a month, or 

 more than some of the best irrigating sec- 

 tions use for the whole year for anything 

 but alfalfa, and more than most of the 

 prosperous alfalfa sections use during the 

 six months of summer, five feet for the 

 whole year being about the outside figure 

 for those who make any extensive business 

 of it and understand it the best. This es- 

 timate of the duty of water on the Bio 

 Grande was made with much care by an 

 engineer of that section for his own infor- 

 mation, was stated in a paper read to the 

 Irrigation Congress at Albuquerque, and 

 was considered correct by those there best 

 qualified to criticise it. It is instructive 

 for three reasons: 



It shows the absurdity of taking the duty 

 of water in that way. 



It shows what progress may be made in 

 irrigation in four hundred years by people 

 who do not travel and study what other 

 sections are doing. 



THE MISTAKES MADE. 



It shows what a big fool the great Amer- 

 ican citizen of the tenth decade of the 

 Nineteenth century can be, for all up and 

 down the Bio Grande, where he is trying 

 to irrigate at all, he is following very 

 closely the old methods of the first Indian 

 settlers, without the slightest suspicion 

 that any other part of the United States 

 has learned anything of late years. When 

 you look at the region under the ditches 

 along that river you will not wonder that 

 Mexico is clamoring for the water that 

 used to come down to the line. Thousands 

 of acres of the most fertile land, under a 



