Monday, August 23, 2010 8/23/10 - water

In today's excerpt - only the tiniest fraction of all the earth's water is available to us as fresh liquid water, and control of rivers, more than oceans or lakes, has been the key to the advance of civilization:

"Despite Earth's superabundance of total water, nature endowed to mankind a surprisingly minuscule amount of accessible fresh liquid water that is indispensable to planetary life and human civilization. Only 2.5 percent of Earth's water is fresh. But two-thirds of that is locked away from man's use in ice caps and glaciers. All but a few drops of the remaining one-third is also inaccessible, or prohibitively expensive to extract, because it lies in rocky, underground aquifers - in effect, isolated underground lakes - many a half mile or more deep inside Earth's bowels. Such aquifers hold up to an estimated 100 times more liquid freshwater than exists on the surface. In all, less than three-tenths of 1 percent of total freshwater is in liquid form on the surface. The remainder is in permafrost and soil moisture, in the body of plants and animals, and in the air as vapor.

"One of the most striking facts about the world's freshwater is that the most widely accessed source by societies throughout history-rivers and streams-hold just six-thousandths of 1 percent of the total. Some societies have been built around the edges of lakes, which cumulatively hold some 40 times more than rivers. Yet lake water has been a far less useful direct resource to large civilizations because its accessible perimeters are so much smaller than riversides. Moreover, many are located in inhospitable frozen regions or mountain highlands, and three-fourths are concentrated in just three lake systems: Siberia's remote, deep Lake Baikal, North America's Great Lakes, and East Africa's mountainous rift lakes, chiefly Tanganyika and Nyasa. ...

"The minuscule, less than 1 percent total stock of accessible freshwater, however, is not the actual amount available to mankind since rivers, lakes, and shallow groundwater are constantly being replenished through Earth's desalinating water cycle of evaporation and precipitation - at any given moment in time, four-hundredths of 1 percent of Earth's water is in the process of being recycled through the atmosphere. Most of the evaporated water comes from the oceans and falls back into them as rain or snow. But a small, net positive amount of desalted, cleansed ocean water precipitates over land to renew its freshwater ecosystems before running off to the sea. Of that amount, civilizations since the dawn of history have had practical access only to a fraction, since two-thirds was rapidly lost in floods, evaporation, and directly in soil absorption, while a lot of the rest ran off in regions like the tropics or frozen lands too remote from large populations to be captured and utilized. Indeed, the dispersion of available freshwater on Earth is strikingly uneven. Globally, one-third of all streamflow occurs in Brazil, Russia, Canada, and the United States, with a combined one-tenth of the world's population. Semiarid lands with one-third of world population, by contrast, get just 8 percent of renewable supply. Due to the extreme difficulty of managing such a heavy liquid -weighing 8.34 pounds per gallon, or over 20 percent more than oil - societies' fates throughout history have rested heavily on their capacity to increase supply and command over their local water resources. ...

"Almost everywhere civilization has taken root, man-made deforestation, water diversion, and irrigation schemes have produced greater desiccation, soil erosion, and the ruination of Earth's natural fertility to sustain plant life.

"How societies respond to the challenges presented by the changing hydraulic conditions of its environment using the technological and organizational tools of its times is, quite simply, one of the central motive forces of history. ... Throughout history, wherever water resources have been increased and made most manageable, navigable, and potable, societies have generally been robust and long enduring. ... In every age, whoever gained control of the world's main sea-lanes or the watersheds of great rivers commanded the gateways of imperial power."

Author: Steven Solomon
Title: Water
Publisher: Harper
Date: Copyright 2010 by Steven Solomon
Pages: 12-16


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