94 



It should be borne in mind that the loss shown in the iibove table is 

 the net loss, as most canals receive more or less inflow from above. 

 In one case this was so ^reat that the canal showed a net gain. Again, 

 the portions of the canals measured represent only a part of the total 

 loss by seepage in the conve3'ance of water from the natural stream to 

 the irrigated fields. No attempt was made to determine the losses in 

 the network of laterals which take the water to the boundaries of the 

 fields. 



The efl'ect produced on the flow of a canal b}- the inflow of seepage 

 from another and higher canal, and the land which it irrigates, is well 

 illustrated b}' the Big ditch. August 9-13, 1900, there was a total loss 

 on this canal from Tilden's ranch to Ilesper farm, a distance of 22 

 miles, of 65 cubic feet per second, or 25.50 per cent of the total flow. 

 In the following year water was turned into a new branch of this same 

 canal known as the High Line, and the seepage from this new branch 

 and from the irrigated farms under it produced a noticeable change in 

 the flow of the main canal. In June, 1902, there was suflicient inflow 

 from the High Line canal to reduce the seepage losses in the main 

 canal to 47.11 cubic feet per second in 33.9 miles, or a total net loss of 

 onl}^ 15.16 per cent. In August of the same year a second series of 

 measurements was made and the total loss was but 9.25 per cent in 30.4 

 miles. The results of measurements made on the same canal in the 

 summer of 1903 show that a still larger quantity of seepage water was 

 admitted from the upper canals which included not only the Higli 

 Line, but also the Yellowstone canal. 



The Yellowstone ditch and also the High Line canal are located at 

 higher elevations than the Big ditch, and it is presumed that a part of 

 the water which escaped from these channels was intercepted by the 

 Big ditch. However, since the combined loss from the channels was 

 27.23 cubic feet per second this alone would not suflice to produce the 

 change previously mentioned in the Big ditch. The balance must 

 have come from irrigated farms. 



The measurements of the Italian and Canyon Creek ditches of Yel- 

 lowstone Valley show that there is a large flow into both ditches. 

 This is readily accounted for by the fact that there arc canals and irri- 

 gated areas above each. 



There was a large increase in the Mill ditch in the third and fourth 

 miles from the head, which would appear to indicate the admission of 

 a ti'ibutar}^ but the increase was wholl}?^ due to seepage water. 



The results of measurements made on the West Gallatin irrigation 

 canal during 1900, 1902, and 1903 diflcr from those of the Big ditch in 

 I'ellowstone Valle}^ in that the former show a somewhat fixed regime. 

 This condition is readil}' accounted for. There are no canals located 

 on higher ground, and consecpiently no irrigated areas from which 

 waste water might drain into the canal. In 1900 the loss from the 



