8 
BULLETIN 83. 
abundant in the residue from the river water, have almost disap¬ 
peared, and we have in their stead sulfates, Glauber and Epsom 
salts forming 65 per cent, of the total mass. All the reservoir 
waters studied show the same changes, but Terry lake alone shows 
it in this extreme degree. Windsor reservoir, however, shows it 
in a very high degree, only a little less than Terry lake. 
The water that is applied to the land then can be said to be 
of two classes, river water taken for direct irrigation and such as 
has been stored. Of late years measures have been taken to util¬ 
ize waste and seepage water wherever available. This may differ 
a little from the stored water but so far as my knowledge goes it 
is seldom more heavily laden with mineral matter than the water 
of Terry lake and we need not consider it as making a separate 
class. 
The amount of mineral substances carried by the river water 
before it leaves the mountains, which is available as plant food, is 
very small, 6.25 pounds of potash per acre-foot and the amount of 
other salts added with such water is of no moment either way. 
But the water taken for direct irrigation seldom reaches its desti¬ 
nation without receiving a decided addition to its stock of mineral 
matter and a considerable increase in the potassic oxid carried by 
it. As the question considered relates to the land to which the 
water is applied, the source from which the potash is obtained 
is not considered but simply the fact that it is contained 
in the water as applied to the soil. The amount of potash in the 
river water ,as distributed on the field, was greater than we have 
found it to contain as mountain water, almost twice as much, but 
it was not a large quantity, only 11.6 pounds per acre-foot. This 
water as a fertilizer was not of much value. It mav have been 
_ j » 1 » 
worth 50 cents per acre-foot. Neither did it carry salts which in 
any reasonable quantities would prove deleterious. The benefit 
derived from the application of this water is from the application 
of the water as such and not from any mineral matter held in 
solution. 
The value added to this water by the presence of organic 
matter and any nitrogen contained in it is also very small, in fact 
as good as nothing, between 60 and 70 cents per acre-foot. While 
we do not add any considerable quantity of directly fertilizing 
salts there is nothing added in sufficient quantities to diminish in 
the least the good that it does. Is the same the case with stored 
waters? We can give only a tentative answer to this question. 
Our soils contain soluble salts whose influence upon our crops is, 
to say the least, of doubtful benefit, and to add more of the same 
sort would not seem to be very wise. We have given the capacity 
of Terry lake as 9,000 acre-feet and its content of salts as 27,000 
tons, all of which is distributed with the water, or allowing one 
