238 THE IRRIGATION AGE. 



At this season of the jrear the streams in the mountains of Color 

 ado would be many times smaller with the same proportional drain- 

 age area. The reason for this is quite easy to explain. It is very 

 probable that there is a greater annual precipitation on the country 

 under consideration than in the Colorado mountains, but this does 

 not materially effect the proportion of the run-off as compared with 

 the precipitation; so we must look for other causes. 



The mountainous country in northern Wyoming is less precipitous 

 and has a deeper covering of soil than in Colorado. These conditions 

 are favorable for a prolonged and uniform discharge of the streams. 

 Then again, there are scattered all through the country we traversed 

 a great number of lakes, ponds, marshes, bogs, soft and grassy 

 meadows, etc., all of which tend to check and equalize the run off. 

 A much greater proportion of the annual precipitation falls in the 

 fall, winter and early spring months in the form of snow than in 

 Colorado; hence a more even distribution of the flow of the streams 

 through the irrigation season, especially when the conditions above 

 mentioned are present to store away in the earth as in a sponge the 

 intermittent supply that comes in the form of rain and snow. 



As I remember the mountain streams of Colorado twenty-five to 

 thirty years ago, from the Cache la Poudre in the north to the Pur- 

 gatoire in the south, they had a much longer "run" of snow water 

 than they now have. The general character of the Wyoming moun- 

 tain streams of to-day and those of Colorado in the early seventies 

 closely resemble each other. In the early days, before the occupa- 

 tion of the mountainous portions of Colorado for mining, stock rais- 

 ing, lumbering, tie-cutting and other purposes whose operations 

 have had the tendency to change somewhat the surface conditions of 

 the gathering ground of the water supply, the volume annually dis- 

 charged by the streams was without doubt greater than the average 

 for the last ten or fifteen years; and instead of the maximum volume 

 caused by the melting of the winter snow occurring from the first to 

 the middle of July each year, it is now fully a month earlier, and the 

 gradual decrease in the volume, or tapering off, of the "summer 

 rise" is now more abrupt, consequently bringing the period of low 

 water earlier in the season. 



For irrigation purposes, the conditions of the water supply that 

 existed in early days in Colorado are preferable to those of to-day, 

 and the query is, to what extent man is responsible for the causes 

 that have wrought these apparent, changes in the character of our 

 water supply within the last thirty years. Are they due in part to 

 climatic changes which may or may not be repeated within a certain 

 cycle of years? and are Colorado and Wyoming likely r,o see these 

 conditions reversed? 



