DRAINAGE BY MEANS OF PUMPING PROM WELLS IN ARIZONA 15 
tends throughout nearly the entire 154 feet of the well's depth is 
shown in Figure 9. The draw-down of the water level in the well 
while being pumped at the rate of 3.5 second-feet is 8.2 feet. Curve 
a, Figure 14, represents the ground-water level before pumping and 
curve b the level attained after the removal of about 373 acre-feet of 
water from the soil during a period of four and one-half months. 
Although the quantity of water which may be recovered from a 
single well of this type is fairly large, the resulting draw-down of 
the water surface is relatively small, and the distance the water level 
was lowered in all directions from the well was one-half mile or more. 
Recently pumping plants with capacity of 11 second-feet have been 
installed in 18-inch wells in sections having underground formations 
of this kind. Operation of these large pumps has shown that under 
the existing conditions perfect drainage may be accomplished at 
distances of more than a mile from the well without causing an 
•*. 15 
3 8 
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1918 
1919 
1920 
1921 
1922 
1923 
A* 
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Water Pt 
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el 
1 , 
AVERAGE OF 1 1 TEST WELLS 
AREA D 
1918 
I9i9 
1920 
!92l 
1922 
1923 
r 
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V 
V 
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7 
8 
; 9 
£ 10 
i II 
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14 
15 
40,000 16 
20,000 17 
1918 
1919 
1320 
1921 
1922 
1923 
rs 
/ 
V 
\ 
\ 
\ 
t 
\ 
\ 
f\ 
V 
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II 
12 
13 
14 
IS 
40,000 16 
20,000 17 
AVERAGE OF 9 TEST WELLS 
1916 
1919 
1920 
1921 
!922 
1923 
s 
40,000' 
20,0001 
AVERAGE OF 23 TEST WELLS 
15 
40,000 16 
20,000 17 
AVERAGE OF 30 TEST WELLS 
1918 
1919 
IS20 
192) 
1922 
1923 
V 
' V 
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V 
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£ 
AVERAGE OF 85 TEST WELLS 
AREA F 
1918 
1919 
1320 
1921 
1922 
1923 
7 
8 
/ 
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\ 
t 
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r\ 
«, 9 
£ 10 
1 II 
£ 12 
$ '3 
14 
15 
40,000 16 
20,000 17 
V 
K 
AVERAGE OF 13 TEST WELLS 
Fig. 12. — Curves showing ground-water level fluctuations! in areas A, B, C, D, E, and F 
excessive draw-down of the water surface in its immediate neighbor- 
hood. Thus fewer pumping plants are required, the cost of install- 
ing and operating the drainage system is less, and the maximum 
lowering of the water level is obtained where it is most needed. 
An interesting comparison of the effectiveness of gravity drains 
with drainage by pumping from wells is afforded by the presence of 
the several closed gravity drains already described as forming a por- 
tion of the drainage system of the Salt River project, and by several 
deep open drains which cross certain areas adjoining the project. 
The closed drain which at first constituted the only means of low- 
ering the water level in area F was considered inadequate for that 
purpose, and pumping from wells has been resorted to as promising 
more desirable results. Table 3 shows the water levels at six test 
wells in October, 1920, just before the drain was constructed, and in 
October, 1923, when it had been in operation two years. These 
records show where water stood highest at the last regular time for 
