CHAPTER IV. 
WATER SUPPLY. 
By G. K. GILBerr. 
The following discussion is based upon a special study of the drainage- 
basin of Great Salt Lake. 
INCREASE OF STREAMS. 
The residents of Utah who practice irrigation have observed that many 
of the streams have increased in volume since the settlement of the country. 
Of the actuality of this increase there can be no question. A popular 
impression in regard to the fluctuations of an unmeasured element of climate 
may be very erroneneous, as, for example, the impression that the rainfall of 
the timbered states has been diminished by the clearing of the land, but in 
the case of these streams relative measurements have practically been made. 
Some of them were so fully in use twenty years ago that all of their water 
was diverted from its-channels at the “critical period”, and yet the depend- 
ent fields suffered from drought in the drier years. Afterward, it was 
found that in all years there was enough water and to spare, and opera- 
tions were extended. Additional canals were dug and new lands were 
added to the fields ; and this was repeated from time to time, until in many 
places the service of a stream was doubled, and in a few it was increased 
tenfold, or even fiftyfold. It is a matter of great importance to the agricul- 
tural interests, not only of Utah but of the whole district dependent on irri- 
gation, that the cause or causes of this change shall be understood. Until 
they are known we cannot tell whether the present gain is an omen of 
future gain or of future loss, nor whether the future changes are within or 
beyond our control. I shall therefore take the liberty to examine somewhat 
at length the considerations which are supposed by myself or others to bear 
upon the problem. 
Fortunately we are not compelled to depend on the incidental observa- 
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