20 BULLETIN" 1456, U. S. DEPARTMENT OE AGRICULTURE 
USE OF PUMPED DRAINAGE WATER FOR IRRIGATION 
A little more than half of all water pumped from wells on the 
project during the season October 1, 1922-September 30, 1923, 
was used for irrigation. The remainder was wasted into natural 
streams, either because the cost of conveying it to lands upon which 
it could be used was too great, or because of its unsuitability for 
irrigation. 
The drainage water used for irrigation is not distributed uniformly 
over the 203,000 acres of cultivated land in the project. Owing 
to the locations of the wells, pumped water can be delivered for irri- 
gation use through only a few of the main canals and laterals. In 
these, it is the practice to mix drainage water with river water. 
Not over 25 per cent of the total quantity of water delivered for 
irrigation use is drainage water and in only one instance is so large a 
proportion of drainage water used. 
The quality of this pumped water governs the degree to which it is 
being used for irrigation. In some wells the quantity of salts carried 
is higher than that usually considered allowable in irrigation water, 
and it is absorbed more rapidly and in greater quantities by the 
soil than is the case with river water. 
There is a diversity of opinion as to the quantity of injurious 
alkali salts that may be permissible in water used for irrigation. It 
is generally conceded that water containing not more than 100 
parts of these salts by weight per 100,000 parts of water may be so 
used safely; that is, upon evaporation of the water the weight of 
the solid material remaining should not exceed 0.1 per cent of the 
weight of the water evaporated. In some sections of the West water 
containing as much as twice this proportion of salts has been used 
without apparent injury to the crops irrigated. However, it has been 
the aim in the Salt River project to keep on the safe side in the 
use of the pumped water. A large number of analyses shows a 
variation in the actual quantity of alkali salts contained in water 
generally delivered to farms from a minimum of 35 parts per 
100,000 parts of water to a maximum of 85 parts per 100,000, and 
the average for all the water used is 45 parts per 100,000. 
The extraordinary degree to which the pumped water permeates 
the soils of the project has had a tendency first to decrease and then 
to increase demand for it. The relatively large quantity required for 
irrigation has discouraged its use unless mixed with a large portion 
of river water. On the other hand, there is a growing demand for 
it for leaching land which had become surcharged with alkali before 
installation of the drainage system. This is due to a general belief, 
which is not without support, that this water is particularly valuable 
for the reclamation of alkali lands, the calcium and magnesium salts 
carried by the water of most of the drainage wells having a tendency 
to make the soil more permeable, thus permitting a more rapid down- 
ward movement of water, which, of course, carries alkali with it. 1 
Aside from its value in draining the land, this method has justified 
its cost by reason of the value of the water for irrigation. The aver- 
age initial cost of the drainage system was $2,904.82 per second- 
1 Rcofield, Carl S. the. alkali problem in irrigation. Annual Report of the Smith- 
sonian Institution, 1921, p. 220. 
