32 
BULLETIN 1257, U. S. DEPARTMENT OF AGRICULTURE 
lished in the Engineering News of August 3, 1916. The projects in 
each age group were separated into three size groups and a curve was 
drawn for all projects included, taken as a whole, and one for each 
of the size groups. The curves for the 1910 census are reproduced 
from those presented in the article. 
For the census of 1920 all projects, regardless of size, were tabu- 
lated by the Census Bureau in age groups, and the results are rep- 
resented by the broken-line curve on Figure 1. 
The curves from the two censuses are not strictly comparable be- 
cause those for 1909-10 are based on only those projects containing 
5,000 acres or more, which represent approximately half the acreage 
irrigated, while that for 1919-20 is based on all projects. 
PER CENT 
OF ACRES 
IRRIGATED 
90 
80 
^k^^^ 
70 
/t 
^■ ou L^n 
— — — 
60 
50 
r<° 
i»0 
M 
\^° 
30 
I 1/ / X 
1 If // 
yr& 
20 
1 
n 
' / // 
VIM 
© 
10 
20 30 ^0 
AGE OF PROJECT IN YEARS 
50 
60 
Fig. 1. — Rate at which hind in irrigation enterprises has been put under cultivation. 
(Based on returns to Thirteenth and Fourteenth Censuses.) 
Inclusion of the small projects has raised the curve for 1919-20 
above those for 1909-10 for the projects of recent date; while it has 
lowered it for the older projects. The latter condition may be ac- 
counted for by the fact that a great many old ditches were not used 
in 1919, in some sections because of lack of water, and in other sec- 
tions because of abnormal rainfall. 
The base for the percentages on which the curves are based is the 
acreage reported as in projects. This figure, in the case of most 
projects, represents the hopes of promoters or owners, rather than 
the area which can be supplied by them, but usually it serves as a 
basis for estimating possible returns and for determining the average 
cost per acre, and consequently the price to be charged per acre for 
water rights. As a consequence, the curves indicate the extent to 
which the land over which the cost is spread is producing something 
with which to meet that cost at various periods after construction. 
