Today, we use water to change the face of the earth. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Technology has always seesawed between two poles -- carving the world to fit our wants one moment, and yielding to the natural order of things the next. That contradiction has always been clearest when we manage earth's water. No ancient technology touched people's lives, or the face of the earth, as strongly as irrigation did. The great Egyptian civilization could be formed only after the arid Nile Valley had been watered.

Our early Southwestern settlers just as surely had to bring water to the land before they could turn from herdsmen-cowboys into settled farmers. But a great change had taken place by then: First, medieval millwrights coupled water-management with power production. Then, during the 1820s and '30s, French and American engineers transformed the medieval water wheel into the modern water turbine. By the mid 19th century, water control had been tied to power generating systems of heroic size.

So the Colorado river caught the minds of engineers as it flowed 1800 miles through the Western deserts -- 200,000 cubic feet of water per second. The Colorado was first explored in 1872. In 1901, a large part of it was diverted into 100,000 acres of the Imperial Valley in Southern California. The desert bloomed until 1905. Then a flash flood inundated the sub-sea-level Valley and wiped out whole towns. It took two years to regain control of the river. By now it was clear that a huge dam and power plant should be placed across the Colorado river.

Then Congress entered the picture. It debated the project through seven presidents, starting with Teddy Roosevelt. Finally Herbert Hoover, one of the great engineers of this century, took office. He immediately gave the green light to a civil engineer named Elwood Mead. Mead began what was at first called Boulder Dam. It was the world's largest concrete structure. Mead took it almost to its completion in 1935. Then he died just months before it opened.

The dam was soon renamed Hoover Dam. Its reservoir, reaching 140 miles back through Nevada and Arizona, is named Lake Mead. The dam couples iron control of irrigation and flooding with 1434 megawatts of power output. Bigger dams have been built since then; but Hoover Dam lit the way to a whole network of huge hydroelectric dams throughout America.

It also represents engineering at its best. In it, the imposition of our will upon the land is coupled with a powerful sense of stewardship toward the earth.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

Stirling, N., The Hoover Dam. Wonders of Engineering. Garden City, NY: Doubleday and Company, Inc., 1966, pp. 113-125.