Irrigation Rushes In
When the Spanish Conquistadors under Coronado set out from Mexico for the – to them – unknown lands to the north, they failed to discover the fabled cities of gold they sought. They did find fields of corn, beans and squash near Native American villages watered by elaborate irrigation canal systems. Without realizing it, they had discovered the real golden technology of the semi-arid Great Plains region.
For a long time, the European settlers who followed didn’t realize the potential value of irrigation to the plains because they had trouble understanding how a “semi-arid” place works. They knew what deserts were. They knew what humid croplands were. But a semi-arid place is not halfway between arid and humid. It doesn’t get half the rain of a humid place.
Semi-arid environments, like the Great Plains, are very dry some years and very wet other years. Still other years are wet or dry at the wrong time of year for the crops that may have been planted there. In semi-arid environments, rainfall is unpredictable and “undefineable.”
Irrigation systems allow farmers to define how much water a crop will get and when. During the 1940s, irrigation technology finally caught up with the need, and there was a steady increase in the number of systems installed on individual farms across the nation.
By 1940, farmers on the plains had been through the Great Depression and the worst drought of the century. They were finally willing to admit that periodic droughts and unpredictable rains were the reality of the plains. A few wet years did not signal the end of drought forever.
If we chart the growth in the number of irrigated acres, we see that the growth rate was relatively flat in the early part of the 20th Century. But between 1940 and 1950, there was a 143 percent increase in the acres under irrigation – from 18 million acres in 1940 to 25.8 million acres in 1950. That was higher growth rate than any decade since.
By 1940, the federal government and private groups had built many of the dams and surface irrigation systems that could be built in the American West. For example, by 1940, 70 percent of the historic flow of the Platte River through Nebraska had been diverted for irrigation already. There was one more major surface water project under consideration – the Pick-Sloan project along the Missouri River.
By 1940, geologists and individual farmers all recognized that there was a huge underground “sponge” called the Ogallala Aquifer below much of the plains containing trillions of gallons of water.
The problem was that it was difficult and expensive to get that water to the surface in large quantities. From the earliest settlement days, farmers had dug wells by hand or used windmills to power small pumps to water livestock or small gardens. In dry years, some farmers realized higher profits from two acres of a garden than from hundreds of acres of dry land crops. But a windmill could produce only a few gallons a minute, not the thousands of gallons needed to irrigate an entire farm.
What they needed was well digging equipment that could drill a hole anywhere from 50 to 500 feet deep. Then they needed a pump that could suck water out of the underground gravel layer and push it hundreds of feet to the surface. And they needed an efficient power plant for the pump with a cheap source of fuel. All three technologies came together in the 1940s.
In this section, we’ll explore the technology of irrigation and the way that irrigation systems developed here are now at work around the world.