DRAINAGE BY MEANS OF PUMPING FROM WELLS IN ARIZONA 13 
has been determined frequently by means of readings over Cipolletti 
and suppressed rectangular weirs. 
Regularly since 1913, observations of a great number of specially 
installed test wells have provided records of the fluctuations of the 
water levels. During the five years before commencement of work 
on the drainage system 97 test wells were observed annually to ascer- 
tain the rate of rise of the ground-water level. In 1918 this number 
was increased to 462 and observations were made thereafter in May 
and October of each year. In October, 1923, the most recent regular 
observation period, water levels were recorded at 834 wells. 
The general effect of drainage is illustrated in Figures 1 and 11, 
which show the reduction of the area having water within 10 feet 
of the ground sur- 
face. Figure 12 shows 
fluctuations of water 
levels and quantities 
of water pumped 
from wells during 
six-month periods for 
the five areas where 
pumping from wells 
has been practiced. 
These curves are based 
on records of those 
test wells only for 
which complete semi- 
annual water-level 
readings for the pe- 
riod 1918 to 1923 are 
available. Locations 
of these test wells are 
indicated in Figure 1. 
It shows a successive 
lowering of the water 
level in each of the 
five areas (A, B, C, 
D, and E) to a depth 
of 10 feet or more be- 
low ground in Octo- 
ber, 1923 ; Table 2 
lists the six test wells 
in each area having 
the highest ground-water level in October, 1923, and the location 
of each. At this time the water level had been lowered suffici- 
ently to permit cultivation of the land over practically the entire 
area. 
All six test wells in area E are in the southeast corner directly in 
line with the underflow from a large tract of partially water-logged 
land lying without the project at the north. This portion of area E 
is therefore a difficult tract to drain, and although four drainage 
pumps are located in it, desirable results probably will not be realized 
until the adjoining area has been drained. On the remainder of area 
E the highest ground-water level in October, 1923, was 6.6 feet. 
§55 
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«9 O ^ O < 
» CM <M 
<M <M »"\J <\ <M <N 
5 5 5 5 5 5 
« o ^ o 
I g 
Fig. 11. — Total areas having various depths to ground water 
