Mar. i f 1924 
Movement of Water in Irrigated Soils 
621 
Table II. — Water-holding capacity of soil of different types , as found at 2 to 4 feet below 
the surface in the field and as determined in shallow perforated cups in the laboratory a 
Samples and texture of soil. 
Average water-holding 
capacity (percentage 
of dry soil)— 
Increase. 
Compara¬ 
tive 
increase. 0 
In the 
field. 
In the 
laboratory. 
No. 5, coarse sand... 
18. O 
21. 5 
20. 7 
33 - 5 
25.4 
36. 6 
4 i. 5 
78. 7 
7-4 
I 5 * 1 
20. 8 
45 - 2 
Per cent . 
41 
70 
IOO 
135 
No. 8, fine sand. 
No. 7, sandy loam. 
No. 4, clay. 
a Reported by Headley from the Newlands Experiment Farm, 1923. 
b Stated as a percentage of the water-holding capacity of the sample in the field. 
THE WATER-HOLDING CAPACITY OF SUBSOIL 
Some observations have also been made at Huntley, Mont., which show 
the water content of the subsoil just below and just above the upper 
limit of free underground water. 3 These were made in connection with 
the putting down of wells to be used for recording the fluctuations of the 
level of the underground water table during the irrigation season. In 
the early spring when these wells were put down the upper limit of the 
saturated zone was encountered between 9 and 12 feet below the surface. 
The water content of the soil in the zone just below the level of the 
ground water is given in Table III. This shows that the saturated 
subsoil contained approximately 25 per cent of water. By reference to 
Table I, which shows the percentage of water in saturated soils of various 
densities, it will be seen that this Huntley subsoil may be assumed to have 
an average density of 99 pounds of dry soil per cubic foot. Thus, each 
cubic foot of the saturated subsoil contains 99 pounds of soil and 25 
pounds of water. This 25 pounds of water per cubic foot is equivalent 
in volume to 4.8 inches of water per square foot of area. 
* In connection with the moisture determinations described above, tests 
were made of the moisture content of the subsoil just above the level 
of the ground water. These latter determinations were made on samples 
representing 6-inch layers, none of which was more than 2 feet above 
the point of saturation, and most of them were within 1 foot above it. 
There were in all 80 moisture determinations on the soil just above the 
water line, and these gave a mean of 24.8 ±0.25. This mean when com¬ 
pared with the mean of 25.4 ±0.2 for the 30 samples reported in Table 
III shows that there is very little difference in the moisture content of 
the soil just above and just below the level of the underground water. 
These results indicate that it takes very little change in the actual 
volume of the underground water to cause a marked change in level. 
It would take only a small contribution of percolating water from above 
to cause the ground-water level to rise; conversely, the removal of a 
small volume of water by drainage would lower the ground-water level. 
The volume relations involved in raising or lowering the ground-water 
level are probably different with different soil types. Very little informa- 
3 These observations were made at the writer’s request by Dan Hansen, Superintendent of the Huntley 
Experiment Farm. 
