AND THEIR RELATION TO IRRIGATION. 
9> 
stream as large as a pencil is highly prized. The stream 
alone could effect no irrigation of consequence, but by 
running into a small reservoir it can be stored, and then 
a large head used for a short time. The greater effective¬ 
ness of a large head is well known in Colorado. In a 
similar way the water from many of the wells, which 
now runs uselessly away, could be made to perform a 
service which would be considerable in the aggregate.. 
Some are already being utilized in this way to a greater or 
less extent, but generally without storing. 
The cost of sinking generally increases more rapidly 
than the depth, so that except in exceptional cases, such as- 
extremely easy boring, as in the San Luis Valley, or great 
supplies of water, as in Dakota, it will not pay to attempt, 
deep wells for irrigation purposes. The temperature 
increases with the depth, which is an advantage if the 
water is to be immediately applied; but the water is also- 
more mineralized, which is a disadvantage or not, accord¬ 
ing to the character of the solids present. 
Throughout the artesian basins of the State it is the 
rule, rather than the exception, to meet with wells whose 
flow is decreasing. This may be due either to the in¬ 
crease in the number of wells, so as to overdraw the local 
supply, or to defects in the individual well. When the 
latter, it is generally due to a partial filling of the well, 
with particles, which may have been brought in with the 
water, or may have fallen from the walls above. In either 
case, the flow is partially stopped, and may generally be 
recovered by cleaning. 
The prevailing troubles of this kind arise mostly 
from the common practice of casing the well imperfectly,, 
or sometimes not at all. Usually in the San Luis Valley, 
and in large numbers of the Denver wells, the casing ex¬ 
tends only through the loose surface soil to the first clay 
stratum. And cases are not unknown where this- 
