276 
Journal of Agricultural Research 
Vol. XXI, No. 4 
The waters of the Colorado River and its tributaries, the Salt and the 
Gila, are so extensively utilized for irrigation that they merit particular 
emphasis in the present connection. These waters have been the subject 
of extensive investigation and careful analysis. The Salt River is 
reported in Table V, on the basis of samples taken at Roosevelt, Ariz., 
as showing a calcium-sodium ratio of 41 to 59. From samples collected 
daily for a year at a point lower down the stream, Forbes has reported in 
detail as shown in Table VI. The analyses made by Forbes show a 
higher salt content than those reported from Roosevelt and a higher 
proportion of sodium. It is clear that the long-continued use of water 
carrying such a high proportion of sodium must tend to produce imperme¬ 
ability in the land unless corrective measures are used. 
The Gila River is characterized by great fluctuations of discharge. It 
drains a large watershed that is subject to torrential rains that gather 
into silt-laden floods. The quantity and character of the more important 
bases carried by this stream are shown in Table VII, which covers the 
period of a year. It will be noted that the calcium-sodium ratio given 
for the Gila in Table V corresponds closely with that reported for the 
summer flood period in Table VII. 
The quality of the water of the Colorado River at Yuma is given for 
seven characteristic periods of a year in Table VIII. It will be noted 
that the main river at Yuma carries less salt and a higher proportion of 
calcium and magnesium than its Arizona tributaries. In this it probably 
reflects the influence of its northern tributaries such as the Green and 
the Grand shown in Table V. 
Table VI.— Analysis of Salt River water samples taken from Arizona Canal at Mesa , 
Ariz., 1899-1990 1 
Period. 
Calcium 
plus mag¬ 
nesium. 
Sodium 
plus potas¬ 
sium. 
Calcium- 
sodium 
ratio. 
i. High and low summer water, Aug., 1899. 
P. p. m. 
85-3 
125.3 
• 100.3 
68.6 
P. p. m. 
134.9 
I 97 -I 
285.4 
325.2 
339.3 
418.5 
39 :6i 
39 :6i 
26 : 74 
21 : 79 
21 : 79 
23 • 77 
2. Summer flood water, Sept. 2 to 9, 1899. 
3. High and low summer water, Sept. 10 to Oct. 9, 1899. 
4. Low winter water, Oct. 18 to Dec. 30, 1899. 
5. Low winter water, Feb. 17 to May 30, 1900. 
72.9 
97-9 
6. Very low summer water, June 1 to Aug. 4, 1900. 
Forbes, R.H. the river-irrigating waters of Arizona. Ariz. Agr. Exp. Sta. Bui. 44, p. 174. 1902. 
Table VII.— Analysis of Gila River water samples taken at head of Florence Canal , 
1899-1900 1 
Period. 
Calcium 
plus mag¬ 
nesium. 
Sodium 
plus potas¬ 
sium. 
Calcium- 
sodium 
ratio. 
1. Low winter water, Nov. 28, 1899 to Jan. 18, 1900.. . 
2. Low winter water, Feb. 1 to Mar. 7, 1900. 
P. p. m. 
78.8 
95-2 
69.2 
118.5 
P. p. tn. 
329.9 
294.5 
104.9 
286.9 
24 : 76 
24 :76 
40 :60 
29 :71 
3. Summer flood water, Sept. 1 to 28, 1900. 
4. Summer low water, Sept. 29 to Nov. 5, 1900. 
1 Forbes, R. H. op. cit., p. 192. 
