DRY-FARMING CONGRESS, WICHITA, 1914 



ST 



that clearing the forests in mountainous regions is followed by drying up 

 springs, greater irregularity of streamflow, and increased erosion. Com- 

 parison of the run-off of various American rivers for different periods made 

 by the Geological Survey and the Forest Service, show that there has been 

 a marged and steady increase in the fluctuation of their flow and in the 

 duration of high and low waters, accompanying the cutting of forests in 

 their upper courses. A careful study of conditions in the White Mountains, 

 recently made by the Geological Survey, established beyond question, for 

 that region at least, that forests have an important influence in reducing 

 the volume and severity of freshets, especially the annual freshets result- 

 ing from the melting of the winter snow. 



May we not, therefore, assume that what has been established else- 

 where applies to our "Western mountains, which are the source of so much 

 water used in irrigation? Let us take, as an example, the Arkansas River, 

 which passes through Wichita. This river rises in the mountainis of Colo- 

 rado, as do a number of other important irrigation streams. Within .the 

 state of Colorado, and in western Kansas, a large part of its water is 

 taken out into ditches and reservoirs. The report of the State Engineer of 

 Colorado for 1911 and 1912 shows that during the latter year 478,935 

 acres were irrigated from the Arkansas and its tributaries within the state. 

 The engineer estimates that twice this area may be put under irrigation. 

 The amount of water used in 1912 was 1,338,851 acre-feet, or about 2.8 

 acre-feet for each acre of land irrigated. 



Now let us see what is the source of this water by which 479,000 acres 

 are irrigated. A number of guaging stations have been established along 

 the Arkansas River from near its source in the high mountains to the 

 eastern boundary of Colorado. These give us very reliable information as 

 to the flow of the stream. Let us take the flow of the stream during 1911 

 and 1912 as representative. Examining the records of the various gauging 

 stations, we find that at Granite, not far from the head of the stream, 

 above which is a drainage area of 425 square miles, the average flow dur- 

 ing 1911-12 was 376 second-feet. At Salida, with a drainage area of 1,160 

 square miles, the flow was 722 second-feet. At Canon City, with a drain- 

 age area of 3,060 square miles, the flow was 892 second-feet. At and 

 below Canon City a great deal of water is taken out of the stream, so 

 that it is best that we should not consider the flow at Pueblo and inter- 

 mediate points, but drop down to Holly, and there to consider the meas- 

 ured flow of the stream, and add to this the total amount of water used 

 for irrigation in the Arkansas drainage. On this basis we find that, if 

 no water had been taken out of the river, the flow at Holly, with a drain- 

 age area of approximately 25,000 square miles, would be approximately 

 2,072 second-feet. 



Presenting these figures in another way, we find that for various ele- 

 vations the run-oft' per square mile of drainage area is as follows: At 

 Granite, elevation 8,930 feet, 613 acre-feet; at Salida, elevation 7,038, 432 

 acre-feet; at Canon City, elevation 5,363, 202 acre-feet; at Holly, elevation 



