DRAINAGE BY MEANS OF PUMPING FROM WELLS IN ARIZONA 6 
successful cultivation of the land. However, it is still somewhat 
higher than it was reported to be in 1903. 
The possible disadvantages of the pumping method are largely 
economic. When the annual operating expense is high, as is likely 
to be the case, there is ever present a temptation to pump insufficient 
water to provide adequate drainage. Expert supervision and a high 
degree of mechanical skill are constantly necessary for the proper 
maintenance and operation of such a system and these are not always 
required for other purposes and might be prohibitive if water is 
pumped for drainage alone. 
Quoting C. C. Cragin, general superintendent and chief engineer, 
Salt River Valley Water Users' Association : 
For small projects, a proper degree of mechanical skill might raise the cost 
of operation considerably above our cost. Our mechanical overhead is very 
low on account of our large power system. Pumps will not drain land unless 
operated and a tendency exists to save operating power costs unless constantly 
watched. The same applies to repairs. A pump shut down too long means 
damage to surrounding land. Daily operating records in the hands of the 
manager of the project are essential. In difficult drainage problems some 
experimentation will undoubtedly be required, and if the project is small this 
may become a serious item from the standpoint of public opinion as well as 
financially. 
In this valley we have not yet found a section which can not be more suc- 
cessfully drained by pumps than by any other method. This may be due and is 
at least undoubtedly affected by the high value to us of the recovered water 
and the cheap hydroelectric power owned by the project. It has, however, 
made possible a clear demonstration of the benefits and wide range of appli- 
cability of this method of drainage. For different conditions the economics of 
the problem may decide against drainage by pumps but, even where power 
must be purchased at commercial rates, the possibility of off-peak arrangements 
would suggest a thorough investigation of the pumping method before discard- 
ing it. 
AREAS REQUIRING DRAINAGE 
The principal areas needing drainage, in which is included all land 
having ground water within 10 feet of the surface, are indicated in 
Figure 1 as A, B, C, D, E, and F. 
In the fall of 1918 when ground water in the valley stood at the 
highest recorded level areas A, B, and C formed a continuous strip 
extending from Phoenix westward along the north bank of Salt River 
to Agua Fria River and thence northward, comprising a gross area 
of 34,336 acres. The three areas constitute the low-lying project lands 
north of Salt River into which descends the drainage from the large 
irrigated area on the north and east. The land has a uniform south- 
westerly fall of from 10 to 15 feet per mile. As may be seen from 
profiles 1, 2, 3, and 4, of Figure 3, drainage outlet for both surface 
and subsurface water is afforded by Salt and Agua Fria Rivers. The 
tracts are similar in surface characteristics but there is considerable 
variation in the character and position of underground formations. 
Area A, as shown by the logs of IT deep wells (figs. 1 and 4 and 
Table 1), is underlaid by strata of clay, caliche, and water-bearing 
gravel and bowlders. The latter formation increases in thickness as 
Agua Fria and New Rivers are approached, indicating that these 
strata are contiguous* to the gravel and bowlders forming the river 
bed. The average depth from the ground to the coarse water-bearing 
formation is a little more than 15 feet. 
