Page 263 - Encyclopedia Of World History Vol V

2040 berkshire encyclopedia of world history

The other form of pressurized system is drip irrigation. economic surplus, full-time division of labor, metal tools,
Developed mainly in Israel (where the need to conserve astronomy, and eventually other sciences. However, peo-
water is great), drip irrigation uses long hoses with holes ple built and operated water management systems for
in them that are buried in the root zone.Water is forced millennia in areas that did not acquire cities and writing
through the hoses and exits the hoses through the holes. (such as New Guinea in the Malay Archipelago and the
People also can put fertilizer and pesticides into the Hohokam people in Arizona).
water, thus delivering them directly to the root zone. Irrigation and drainage change the water balance of
These systems are even more efficient than sprinkler sys- the landscape, and along with agriculture they change the
tems, approaching 0 percent water loss, and they save on plants and animals there. In order to safely grow our
the labor to apply fertilizer and pesticide. A major dis- domesticated plants and animals people have wanted to
advantage, of course, is the cost in energy to run the sys- eliminate plants and especially animals that are danger-
tem. Another disadvantage is that the holes in the pipes ous. Lions, tigers and elephants have been hunted and
can clog. Clogging requires that the hoses be exposed, killed. The entire landscape has been changed in ways
which means excavating them, with possible damage to that we could call domestication.At the same time, how-
the crops. ever, we have provided habitats for small dangerous life
forms, such as malaria.The blessings are mixed.
Water Management The simple tools and knowledge needed to build and
in History operate irrigation systems and drainage systems exist
People have used irrigation systems and drainage systems everywhere, and traditionally there was little variation
to manage water for thousands of years and have built in the forms of such systems. With the Industrial Rev-
and operated such systems without writing and without olution, however, the scenario changed. European colo-
scientific laboratories. The relationship between water nial powers built large storage dams during the
stress (too much, too little) and the health of a green plant nineteenth and twentieth centuries, using industrial
is obvious to any intelligent observer. People can use sim- technology. Storage dams were not new, but the scale
ple tools, easily made, to loosen and move dirt to dig of them was. The practice of lifting water with heat
ditches. Ditches will not function if their layout is wrong engines diffused widely, and this practice, too, used an
because water will not flow uphill in an open ditch.Trial, industrial technology. Today people everywhere use
error, and correction are part of the success. A modern heat engines linked to pumps, replacing traditional
scientific understanding of water, green plants, soil, solu- systems. Significantly, the technology is also manufac-
tions, the hydrological cycle, and photosynthesis began tured just about everywhere.
during the nineteenth century and is still generating
knowledge. People needed instruments (microscope, ther- The Future
mometer, balance) and the disciplines of physics, chem- The future of water management is a cloudy one.World
istry, anatomy, and physiology to achieve the scientific population is growing, and such growth will increase the
knowledge that we now have. demands for food and for space for buildings. A sub-
The impact of irrigation and drainage on world history stantial portion of the world’s food is now grown with
has been great. Irrigation and drainage permit people to irrigation, and this portion will only increase in the near
grow crops where otherwise it would be difficult or future.An easy way to gain space to build is to drain wet-
impossible.The growing of crops in turn permits a larger, lands.With industrial technology and (cheap) energy we
denser population. Some scholars have claimed that civ- have the technical capacity to build and operate large
ilization itself could not have occurred without irrigation water management systems.
and drainage. If that is true, these technologies have been However, the best places for storage dams have already
important in the birth of cities and have played a role in been taken, and finding new sources of water will be