Man and Nature; Or, Physical Geography as Modified by Human ActionMarsh, George P. (George Perkins)
Science
Man and Nature; Or, Physical Geography as Modified by Human Action
Marsh, George P. (George Perkins)
Conservation of natural resources; Human geography; Nature -- Effect of human beings on; Physical geography
The fields of Egypt are more regularly watered than those of any other
country bordering on the Mediterranean, except the rice grounds in
Italy, and perhaps the _marcite_ or winter meadows of Lombardy; but
irrigation is more or less employed throughout almost the entire basin
of that sea, and is everywhere attended with effects which, if less in
degree, are analogous in character to those resulting from it in Egypt.
In general, it may be said that the soil is nowhere artificially watered
except when it is so dry that little moisture would be evaporated from
it, and, consequently, every acre of irrigated ground is so much added
to the evaporable surface of the country. When the supply of water is
unlimited, it is allowed, after serving its purpose on one field, to run
into drains, canals, or rivers. But in most regions where irrigation is
regularly employed, it is necessary to economize the water; after
passing over or through one parcel of ground, it is conducted to
another; no more is withdrawn from the canals at any one point than is
absorbed by the soil it irrigates, or evaporated from it, and,
consequently, it is not restored to liquid circulation, except by
infiltration or precipitation. We are safe, then, in saying that the
humidity evaporated from any artificially watered soil is increased by a
quantity bearing a large proportion to the whole amount distributed over
it; for most even of that which is absorbed by the earth is immediately
given out again either by vegetables or by evaporation.
Public-domain text, read in full here on John Shaqi.
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