Mar. i, 1924 
Movement of Water in Irrigated Soils 
671 
THE MOVEMENT OF UNDERGROUND WATER 
The water that accumulates in the subsoil of an irrigated field is often 
thought of as similar to bodies of open water, such as lakes or ponds or 
as a continuous body of uniform quality and that if it is tapped by a drain 
its quality may be determined by sampling the drainage water just as 
we would sample a stream that flowed from a lake. If it were desired 
to know the quality of the water in a lake it would not be thought neces¬ 
sary to obtain samples from many different places in it. There might be 
slight differences in the quantity or character of the dissolved material as be¬ 
tween the surface and the bottom of a lake or between points where springs 
or streams flowed into the main body of water. In an open body of water 
such differences are usually slight and they are still less in moving water 
such as streams. The movement of water results in thorough mixing, 
Pi G g_Ground-water levels, series Y south, Newlands Experiment Farm; irrigated Sept. 28 
to 30,1922. 
so that a sample taken at one place in a stream is found to be much like 
a sample taken at another place in the same stream. 
When we find that a drain is drawing water from the saturated subsoil 
of a field we are likely to assume that a sample of this drainage water 
may be taken as representative of the accumulated subsoil water of that 
field. As a matter of fact, a more detailed investigation of such a situa¬ 
tion would be likely to show that samples of water obtained from the 
saturated subsoil in different parts of the field contained very different 
quantities of dissolved material. 
The analogy of the drainage discharge from an irrigated field is not with 
a stream discharging from a lake but rather with a stream discharging 
from a swamp. In an open lake the water is free to move as in response 
to the wind, while in a swamp the movement of the water is restricted 
by islands and other barriers. A stream may flow through a swamp by 
way of a number of channels and not come in contact or mix with water 
