THE IRKIGATION AGE. 



205 



product of the depth in feet and the width of the 

 stream in feet) multiplied by the velocity in feet per 

 second will equal the number of second-feet. For ex- 

 ample, if the area of the cross-section of the stream 

 be two square feet, and the velocity one foot per second, 

 the flow of the stream would be two second-feet; or, 

 if the area were the same and the velocity three feet 

 per second, the flow would be six second-feet. 



In ditches with earthen (and consequently more or 

 less irregular) walls the area of the cross-section is ob- 

 tained by multiplying the average depth by the average 

 width. The placing of a flume in a ditch or other chan- 

 nel makes the shape of the stream flowing through it 

 regular in that part of it, and thus furnishes a more 

 convenient place for ascertaining the area of the cross- 

 section. If the flume be made a certain width as two 

 feet, four feet, or eight feet only the depth of the 

 water need be ascertained in making computations. 



The velocity of a stream is ascertained with more 

 difficulty than is the size of it. By means of a float the 

 velocity of the surface may be ascertained quite accu- 

 rately, and from this the velocity of the stream as a 

 whole estimated. For example, if a float be 40 seconds in 

 passing between two points 100 feet apart, the surface 

 velocity would be 2y^ feet per second. But the surface 

 of a stream moves faster than the parts of it that come 

 in contact with the bottom and sides ; hence the velocity 

 of the whole stream is less than that of the surface, 

 how much less depending upon the nature of its walls. 

 For obtaining the approximate flow of a stream, the 

 velocity of the stream may be considered as .8 of the 

 surface velocity. Thus, if the surface velocity be 2^ 

 feet per second, the velocity of the stream as a whole 

 may be considered as 2 feet per second. 



A more accurate means of obtaining the velocity of 

 a stream is furnished by the instrument known as the 

 current meter. By its use the velocity of all parts of a 

 stream may be quite accurately ascertained, and from 

 these data the velocity of the stream as a whole cal- 

 culated. 



The necessity of obtaining the ve!6city of a stream 

 to be measured may be obviated by causing the water to 

 flow over a weir placed in the channel. By this arrange- 

 ment only the width and depth of the stream need be 

 considered. But a measuring weir can be used only 

 where there is considerable fall in the bed of the stream 

 to be measured, most of the ditches in the Salt Eiver 

 valley having too little fall for this purpose. The Cip- 

 poletti weir is the one now generally used where condi- 

 tions are favorable. 



The following is the most practicable simple 

 method of water measurement in this region : Place in 

 a straight part of the stream a plain flume eight to six- 

 teen feet long, and of a definite width. Then ascertain 

 by a float or a current meter, what the velocity is when 

 the water flows at each of various depths, in the flume. 

 By checking the water some distance back of the flume, 

 and letting pass through definite varying amounts, it 

 can be thus caused to flow through the flume to the 

 depth of one inch, one and one-half inches, two inches, 

 and so on, successively. By ascertaining and recording 

 the velocity of the stream as it flows through at vari- 

 ous depths, the flow of the stream at these depths can be 

 tabulated and kept for future reference. If the banks of 

 the ditch above and below the measuring flume be kept 

 in the same condition as when the guaging of the fhime 



was done, the flow may be ascertained at any time by 

 noting the depth of the water and referring to the table 

 prepared. The measurement of the depth of the water 

 should be made midway between the two ends of the 

 flume, which should be placed and maintained in a hori- 

 zontal position in both directions. For convenience, a 

 thin- ruled measure may be tacked to one side of the 

 flume. 



AMOUNT OF WATER USED UPON FARM. 



A beginning was made during 1900 in keeping a 

 record of the amount of water used upon the farm and 

 of that applied during the development of individual 

 crops. Unfortunately, the farm is not so situated that 

 the measurement and division of the water that flows 

 upon it is an easy task. The fall of the ditch leading to 

 the farm and of the ditches upon the farm is too slight to 

 make the use of Cippoletti weirs possible. Hence it has 

 been necessary to measure the water in flumes placed at 

 the same level as the bottom of the ditches. The tri- 

 angular shape of the farm has increased the difficulties. 

 However, it is believed that a fairly accurate record has 

 been kept, and that a close approximate to the water 

 actually applied has been obtained. As the work of 

 recording the water has progressed during the two years, 

 experience has made it possible to make more accurate 

 measurements and keep more accurate records. 



A record of the depth and the duration of each 

 "run" of the water flowing through the ditch that sup- 

 plies the twenty-eight acres of the station farm involved 

 in this report, and a few small farms lying below it, is 

 made by a water-register situated at one side of a 

 gauged box placed in the ditch at the upper margin of 

 the farm. A Y-shaped division box a short distance 

 below the register separates the portion to which the sta- 

 tion farm is entitled from that which is to flow on 

 through the farms below. The station contracts with 

 the water company for the delivery of 33 1-3 inches 

 (the amount of its so-called water right) from the 

 Grand Canal, and a varying number of inches from the 

 Maricopa Canal. The farmers below contract for the 

 delivery of forty to sixty inches of Grand Canal water 

 and twenty to thirty inches of Maricopa water. Thus, 

 when water was flowing from the Grand Canal, and 

 forty inches had been contracted for by the farmers be- 

 low, the station was entitled to thirty-three and one- 

 third, seventy-three and one-third, or five-elevenths, of 

 the total amount flowing in the ditch ; and when water 

 was flowing from the Maricopa Canal, the station was 

 entitled to another definite fractional part of the total 

 amount. These fractional portions of the amount that, 

 according to the water-register, passed through the 

 ditch are taken as the amounts used upon the twenty- 

 eight acres of the station farm during the different 

 "runs." It is to be understood that after contracting 

 with the water company, which under our existing sys- 

 tem has entire control of the distribution of the water 

 to users, the station has no voice as to the amount of 

 water that shall pass through the ditch leading to the 

 farm, its only prerogative in the matter being to prop- 

 erly separate its portion from the remainder of the ditch 

 content. 



The amount of water used upon the twenty-eight 

 acres of the station farm supplied with water from the 

 ditch mentioned above, during each month of the period 

 during which a record was kept, is as follows : 



