DRAINAGE 
ates and carbonates of calcium, sodium 
and magnesium. 
An accumulation of alkali on the sur- 
face of land is not the cause of the land 
being unproductive, but is rather the re- 
sult of a high water table which is the 
primary cause for the unproductiveness. 
The surface accumulation of alkali be- 
ing a result rather than a cause, the only 
permanent method of removing it is to 
remove the cause, namely the water, and 
this can be done only by some method 
of drainage. Alkali being readily solu- 
ble in water is brought to the surface by 
capillary attraction and is deposited as 
the water evaporates. If then the ground 
water can be kept in the ground deep 
enough to prevent its evaporation from 
the surface there can be no alkali depos- 
ited. This depth depends upon so many 
things that it is difficult to specify ex- 
actly what it should be. In coarse 
grained soils such as sand or gravel 
water will not rise from as great a depth 
as in the finer grained soils such as the 
ordinary volcanic ash of the arid regions 
of Washington. The condition of the 
surface of the soil also has its influence 
on the rise of ground water by capillarity. 
The water can stand closer to the sur- 
face without injury on land that is well 
cultivated than it can on land whose sur- 
face is hard and compact. Land growing 
crops which shade the land, such as al- 
falfa or clover, are less subject to alkali 
than land which is bare. Under ordinary 
conditions and in soil similar to that 
which is ordinarily found in the Yakima 
valley, the ground water should never be 
allowed to come closer than five and one- 
half or six feet of the surface. 
One of the fundamentals of drainage 
in irrigated sections is not only to take 
off surface water but to maintain a water 
table below the limit of capillarity and 
to do this it is generally necessary to 
have drains at least six feet deep. 
The gridiron system of tiling which is 
used in the humid sections is seldom em- 
ployed in irrigated sections as the water 
generally comes from some definite direc- 
tion and can be intercepted or cut off 
by drains located so as to catch the water 
before it reaches the land. 
909 
It is very essential that the individual 
tract to be drained be carefully studied 
as to subsurface conditions. By this is 
meant that a drainage system cannot be 
accurately planned without a _ definite 
knowledge of where the water is coming 
from, the location and depth to hard-pan 
if there is any, the nature of the subsoil, 
whether sand, gravel or loam and the 
nature of the surrounding land, whether 
irrigated or dry, flat or sloping. 
In gravelly soils or soils with a gravel 
subsoil it will be almost universally found 
that the water is traveling in the gravel 
and that such lands drain readily and for 
a considerable distance from the drain. 
On account of the distance that this kind 
of land will drain the principal difficulty 
is in determining the amount of water 
which it will be necessary to handle. 
In land which has a hard-pan stratum 
or strata beneath the surface, the diffi- 
culties are increased. It may be found 
that water is traveling on top of the hard- 
pan or it may be beneath or both above 
and below. If the water is below the hard- 
pan it is often found that it is under 
slight pressure and is forcing its way up 
through the hard-pan. In such cases drains 
located so as to cut through this strata 
will often relieve the pressure and carry 
away the excess water. When the water 
is found to be on top of the hard-pan 
some method of intercepting it should be 
planned. It is not always possible to 
reach this water at the proper place and 
depth to give relief, and it must pass too 
close to the surface before reaching the 
drains. 
Dynamite has been used to break up 
the hard-pan strata so as to allow a freer 
passage through the soil, where it is 
closer than three or four feet to the sur- 
face. It is seldom that by dynamiting 
the land alone relief can be secured, as 
there must be some means provided 
whereby the water can escape. Hard-pan 
can be successfully broken by exploding 
from one-half to one stick of 20 per cent 
stumping powder at intervals of 15 to 
25 feet. The depth and distance apart 
should be governed by the depth and 
thickness of the hard strata. 
Attempts have been made to rid land 
