When we look at a chart of worldwide totals of irrigated area from 1800 to 2002, we see a gradual increase until 1950 when the curve shoots up. (If you want to replay the animation again, hit the "Reload Page" button on the browser.)
"During the heyday of dam-building, from the 1950s to the mid-1970s," says Sandra Postel, "about 1,000 large dams came on-line every year."
In the U.S., the total area of irrigated land doubled from 10 million hectares in 1950 to 21 million hectares in 1995. (To put that in more familiar terms, we went from almost 25 million acres in 1950 to 52 million acres in 1995.)
In very real ways, the Green Revolution was actually a massive export of technology and know-how from the U.S. to hungry, developing nations around the world. During the '50s and '60s, the U.S. Bureau of Reclamation was completing one massive dam project after another in the American West. In addition, the Bureau became a training ground for engineers from many developing countries. The indomitable Floyd Dominy was Commissioner of the Bureau of Reclamation from 1959 to 1969. "Everywhere I went in India," Dominy boasted, "they thought I was the second coming of the Buddha."
Yet, if we look at the growth of irrigation in another way as total area per thousand people on the earth irrigated land leveled off sharply beginning in about 1962 and has even begun declining in recent years. World population keeps increasing at a frightening rate. Most of the major rivers that can be dammed have been dammed. So much water from rivers is being diverted that rivers like the Colorado, the Ganges, the Indus, the Nile and the Yellow and Fen rivers in China are running dry. Lakes are shrinking, like the Owens in California, the Galilee and Dead Sea in the Middle East, the Aral in Kazakhstan and Lake Chad in Aftrica. Underground water tables are dropping and irrigation pumps are being turned off in the U.S., Mexico, Spain, Saudi Arabia, Israel, India and China.
The boom of the '50s and recent slowing of irrigation is important because we have come to rely on irrigation projects to feed our growing populations. Nearly 70 percent of global water use goes to agriculture. In contrast, only 20 percent goes to industry and 10 percent to domestic or household use.
To put it another way, 60 percent of the world's grain is produced using irrigation. So, if today's farmers are going be able to keep up with expanding demand for food and if the era of quickly expanding irrigation is over they are going to have learn, as Sandra Postel puts it, how to get "more crop per drop."
Written by Bill Ganzel, the Ganzel Group. First published in 2006. A partial bibliography of sources is here.