12 LANDS OF THE ARID REGION OF THE UNITED STATES. 
THE USE OF SMALLER STREAMS SOMETIMES INTERFERES WITH THE USE OF 
THE LARGER. 
A river emerging from a mountain region and meandering through a 
valley may receive small tributaries along its valley course. These small 
streams will usually be taken out first, and the lands which they will be 
made to serve will often lie low down in the valley, because the waters can 
be more easily controlled here and because the lands are better; and this 
will be done without regard to the subsequent use of the larger stream to 
which the smaller ones are tributary. But when the time comes to take out 
the larger stream, it is found that the lands which it can be made to serve 
lying adjacent on either hand are already in part served by the smaller 
streams, and as it will not pay to take out the larger stream without using 
all of its water, and as the people who use the smaller streams have already 
vested rights in these lands, a practical prohibition is placed upon the use 
of the larger river. In Utah, church authority, to some extent at least, 
adjusts these conflicting interests by causing the smaller streams to be taken 
out higher up in their course. Such adjustment is not so easily attained by 
the great body of people settling in the Rocky Mountain Region, and some 
provision against this difficulty is an immediate necessity. It is a difficulty 
just appearing, but in the future it will be one of great magnitude. 
INCREASE OF IRRIGABLE AREA BY THE STORAGE OF WATER. 
Within the Arid Region great deposits of gold, silver, iron, coal, and 
many other minerals are found, and the rapid development of these mining 
industries will demand pari passu a rapid development of agriculture. Thus 
all the lands that can be irrigated will be required for agricultural products 
necessary to supply the local market created by the mines. For this pur- 
pose the waters of the non-growing season will be stored, that they may be 
used in the growing season. 
There are’ two methods of storing the waste waters. . Reservoirs may 
be constructed near the sources of the streams and the waters held in the 
upper valleys, or the water may be run from the canals into ponds within 
or adjacent to the district where irrigation is practiced. This latter method 
will be employed first. It is already employed to some extent where local 
