May 1 6 , 1921 
Quality of Irrigation Water 
277 
Table VIII .—Analysis of Colorado River water samples taken at Yuma, Ariz., igoo- 
igoi 1 
Period. 
Calcium 
plus mag¬ 
nesium. 
Sodium 
plus potas¬ 
sium. 
Calcium- 
sodium 
ratio. 
1. Low winter water, Jan. 10 to Mar. 26, 1900. 
P. p. m. 
106.3 
68.6 
53.8 
57-8 
98.7 
152.5 
II 9 * 7 
P. p. m. 
200. s 
174.2 
65.1 
89.2 
164.0 
203.0 
171-7 
35 =65 
28 : 72 
45 : 55 
39 : 61 
38 : 62 
43 : 57 
4 i : 59 
2. Rising summer water, Mar. 27 to Apr. 31, 1900... 
3. High summer water, May 1 to June 29, 1900. 
4. Low summer water, June 20 to"Aug. 26,1900. 
5. Summer flood water (local), Aug. 1 to Oct. 1, 1901.. 
6. Summer flood water (Ariz.) Oct. 2 to Nov. 19, 1900. . 
7. Low winter water, Nov. 20, 1900, to Jan. 24, 1901... 
1 Forbes, R. H. op. cit., p. 205. 
These data with respect to some of the more important irrigation 
streams of the western United States show that in general these waters 
carry a higher proportion of sodium than the Nile. If our present 
hypothesis is correct it may be found advisable to remedy this condition 
by supplying calcium, or some other high valent base such as aluminum, 
in soluble form to the land or to the irrigation water. There are marked 
differences in irrigated lands under the same water supply with respect 
to the tendency to become impermeable with continued irrigation. 
Further investigation may be expected to explain these differences and 
may point the way to correcting difficulties that are now acute. 
SUMMARY 
(1) On certain irrigated lands in the western United States the soils 
are not readily permeable to water and become hard and difficult to work 
into good tilth when dry. 
(2) In extreme cases such soils are relatively unproductive because 
they do not absorb a sufficient quantity of water from periodical irri¬ 
gations to supply the crop plants, particularly during hot, dry weather. 
(3) Where the soil is not readily permeable to water it is sometimes 
difficult to wash out the excess of soluble salts that may be present in such 
quantities as to injure crop plants. 
(4) This hardness or impermeability of the soil is believed to be due to 
the effect of sodium on the clay in the soil. 
( 5 ) A soil may become hard and its permeability become reduced by 
irrigating with water containing sodium carbonate. 
(6) Similar results may follow when soils containing excessive quan¬ 
tities of sodium chlorid or sodium sulphate are leached with pure water. 
(7) In the presence of certain other bases such as calcium or aluminum, 
in appreciable quantities and in soluble form, the injurious action of 
sodium on the clay does not take place. 
