(2 of 6)
The weakness of the Columbia dates from the ice age, when a glacier blocked its deep canyon and forced it to cut a new channel. The river returned to its old bed after the glacier retreated, but the temporary channel (the Grand Coulee) is still there, a spectacular, steep-walled dry valley that leads to a cluster of level, irrigable plains.
Displaced River. A dam high enough (more than 600 feet) to turn the Columbia directly into the Coulee would have backed the water far into Canada. So the dam was built to raise the water level about 350 feet. A small part of the electric power that its turbines generate is used to pump part of the river the rest of the way (280 feet) and spill it into the Coulee. This turbine-pump combination, using a river's energy to raise part of its water over its own high banks, is the key engineering trick that frees irrigation from gravity. Its efficiency is about 80%, i.e., one cubic foot of water falling 100 feet generates enough electricity to pump another cubic foot 80 feet above the reservoir.
Eventually Grand Coulee will have twelve pumps, housed in a long, tall room with the proportions of a cathedral nave. Two are already installed, driven by the most powerful (65,000 h.p.) motors in the world. Each can pump enough water (one billion gallons a day) to meet the needs of New York City. All twelve pumps together will lift 16,000 cubic feet per second—close to the average flow of the Colorado River.
Displaced Rattlers. Last week one pump was running, slowly filling a 27-mile lake in the desert-bottomed Coulee. As the water advances, it pushes ahead of it a wave of displaced rattlesnakes. One bu-reauman killed 51 in a morning.
When the water has filled the lake, it will creep through branching canals that lace like arteries through the plains. It is mournful country now, far more depressing than self-respecting desert. In rainy years, some parts of it produce a fair crop of wheat; successive waves of settlers have tried to make a go of wheat farming. Nearly all have failed and fled. Their houses stand empty, surrounded by grey-green sagebrush, symbols of desolation.
The present wave of settlers, the bureau is sure, will not fail. Next spring, Grand Coulee's water will ripple down the ditches, bringing dependable "rain" to 87,000 acres. Each year thereafter, more blocks of land will get water, until the whole million acres have turned green.
Moist Magic. It will be very green, for irrigated land outproduces most land that is only "sky-watered." Desert soil has not been leached by heavy rain of its soluble plant nutrients. The sunlight keeps plants awake and growing. Most important of all, a skilled irrigator can give his plants just the right amount of water. Natural rainfall seldom does this; most seasons have wet or dry spells that check plant growth.
Out in the sagebrush, the bureau's experimental farms, now watered from pumped wells, look like green postage stamps pasted on brown paper. One acre of their pasture supports three head of cattle. The bureau's farmers have harvested 160 bushels of grain sorghum per acre, five tons of alfalfa hay, 32 tons of sugar beets. The U.S. average is 23.1 bushels of sorghum per acre, 2.23 tons of alfalfa, 14.8 tons of beets. Figures like these excite the settlers, who clamor for many times as much land as can be watered next season.