204 



THE IKRIGATION AGE. 



indicate what can be done by co-operation under the 

 provisions of the Carey Act. If there is a tetter way for 

 the Government to dispose of its desert lands the pro- 

 cedure has yet to be defined by law. The Carey Act 

 is limited and its operation is temporary. There is no 

 reason why this should be so. Congress ceded 1.000,000 



IRRIGATION EXPERIMENTS IN ARIZONA. 



Investigations Covering a Period of Four Years at the Experiment 

 Station Farm at Tucson. 



SIDON CANAL, WYOMING. VIEW LOOKING UPSTREAM, ONE- 

 HALF MILE BELOW HEADGATE. 



acres to each arid State under certain conditions and 

 then restricted the time in which canals and other irri- 

 gation works might be constructed. There is a ques- 

 tion as to whether the act does not expire as far as 

 new projects are concerned on the 16th of next August. 

 It is difficult to understand the reason for curtailing 

 the development that might be possible under this law 

 by these restrictions. But few companies and fewer 

 individuals care to undertake the construction of expen- 

 sive works when the time for complete irrigation and 

 reclamation is fixed at a date that makes the accom- 

 plishment of the task almost impossible. The lands 

 not reclaimed at the expiration of this time revert to 

 the Government and the investor is the loser. This is 

 by far the law best adapted to the needs of the arid 

 region. It is the one that is liable to fail first. The 

 Desert Land Act is next in value and it has been threat- 

 ened for the past four years. If both should be re- 

 pealed or become inoperative, practically no great devel- 

 opment can take place under private enterprise. 



Raymond F. Walter, of the U. S. Geological Survey, 

 expects to establish six stations in the western part of 

 South Dakota for the purpose of determining the 

 amount of water available for irrigation purposes. One 

 of these will be on the Belle Pourche river, on, Redwater 

 creek, one on Spearfish creek, one on the Cheyenne 

 river, near Edgmont, and two others, the location of 

 which has not been decided upon. After ascertaining 

 the amount of water available for irrigating, which 

 would include the rainfall, Mr. Walter will turn his 

 attention to the location of natural reservoir sites, 

 some twelve or fifteen of which have been petitioned 

 for by residents of the region. He will determine 

 whether or not they are practicable for conserving the 

 flood water for irrigation purposes, with particular at- 

 tention to the expanse of tillable land tributary, onto 

 which water may be carried by ditches from the pro- 

 posed reservoirs. 



BY PROF. ALFRED J. M CLATCHIE, 



Agriculturist and Horticulturist of the Arizona Agricultural Experiment 



Station. 



[CONTINUED.] 

 METHOD OP MEASURING WATER. 



For measuring flowing water two different units 

 of measurment are in use : the miner's inch and the sec- 

 ond-foot. The miner's inch is supposed to be the 

 amount of water flowing through an opening an inch 

 square, under certain conditions. In most regions 

 where the unit is used, the opening is supposed to be 

 so placed that there will be a certain depth of water 

 above it, causing some pressure. The required depth 

 of water above the aperture varies in different regions 

 from four to six inches, while in some localities the 

 aperture is not required to be below the surface of the 

 water from which the stream is flowing. There being 

 a lack of uniformity in the conditions under which, 

 a miner's inch is measured, the amount of water ex- 

 pressed by the term is plainly not a definite quantity. 

 Moreover, without a complicated device, it is imprac- 

 ticable to control the depth of water above the open- 

 ing; and consequently a miner's inch of water could 

 not be easily accurately measured out, even if the re- 

 quired conditions were the same in all localities. 



The second-foot is a much more convenient unit 

 of measurement, and is the one that is becoming gen- 

 erally adopted for the measurement of irrigating water. 

 A second-foot is the flow of a cubic foot of water dur- 

 ing each second of time. Thus, a second-foot flow of 

 water for one minute would equal just sixty cubic feet, 

 a second-foot flow for an hour just 3,600 cubic feet 

 of water, and so on. Since the second-foot is always 

 a definite flow of water, a second-foot flow for any defi- 

 nite period will equal a definite number of cubic feet 

 of water. It thus becomes easy to compute how much 

 irrigating water will flow upon a given piece of land 

 in a given time. Since there are 43,560 square feet 

 in an acre of land, it will take 43,560 seconds, or 12.1 

 hours, for a second-foot flow to cover an acre with water 

 to the depth of a foot. Enough water to cover an acre 

 a foot deep is termed an acre-foot. The flow of one 

 second-foot for 12.1 hours, or of one-half a second- 

 foot for 24.2 hours (twenty-four hours and twelve min- 

 utes) therefore equals an acre-foot. A second-foot flow 

 for twenty-four hours so nearly equals two acre-feet 

 (enough water to cover one acre two feet deep, or two 

 acres one foot deep) that in making computations on 

 farms it may be considered as equaling that amount, 

 without the error being great enough to cause the arrival 

 at serious misleading conclusions; and in most cases 

 the error would not be greater than the errors likely 

 to occur in making the measurements of the stream from 

 which the computations were made. In this region 

 an "inch" is now considered to be one-fortieth of a 

 second-foot, the latter thus equaling forty local "inches." 

 In making computations, a second-foot and forty "inch- 

 es" may be used interchangeably, therefor. 



To ascertain the number of second-feet flowing in 

 a ditch or other channel, it is necessary to determine 

 the size of the stream (the area of its cross-section) 

 and its velocity. The area of the cross-section (the 



