The World in 2050: Four Forces Shaping Civilization's Northern Future

Despite its endless recirculation, there are parts of the hydrologic cycle that smell suspiciously like depletion of a finite natural resource. This is especially true for underground sources, collectively called groundwater.

Groundwater is a very attractive water source. Unlike rainfall and rivers, which have tiny holding capacity and variable throughput, aquifers hold large volumes and are relatively stable. Humans have dug wells for thousands of years—the Egyptians, Chinese, and Persians had them as early as 2000 B.C. However, wells more than seventy to eighty feet deep are a modern invention, brought about by centrifugal pumps and the internal combustion engine.²²⁸ In water-scarce areas this new technology quickly triggered a water-drilling boom, much like the oil-drilling boom described in the previous chapter. We became a horde of mosquitoes, piercing and probing the planet with steel proboscises in search of fluids.

Tapping subterranean water meant that farmers could convert drylands and deserts into lush, productive fields virtually overnight. Here’s a dirty little secret about the agricultural “green revolution” of the latter half of the twentieth century. The green revolution was brought about not only by new petrochemicals, hybrid seeds, and mechanized agriculture, but also by a massive ballooning in the pumping of groundwater to irrigate crops. In just fifty years the world’s irrigated land area doubled from 60 million acres in 1960 to 120 million and growing by 2007.²²⁹ Much of that irrigation water came from underground. Today, many farmers in California, Texas, Nebraska, and elsewhere are utterly dependent upon groundwater for their livelihoods.²³⁰

A common misconception about groundwater arises from photographs of headlamp-wearing spelunkers wading through mysterious dark pools in underground caverns. Actually an “aquifer” is rarely a subterranean river or pool but instead just a geological layer of saturated sediment or bedrock, the best material being porous sand.²³¹ Water is removed from the aquifer by drilling a hole into the layer and installing a pump to raise water to the surface. This creates a cone of depression in the water table, causing surrounding groundwater to ooze through the porous matrix toward the borehole, providing a continuous water supply. Water raised from deep aquifers is normally reliable, clear, cold, and delicious. Deep aquifers don’t flood or go into drought. In some of our driest, most water-stressed civilizations, it is the discovery and tapping of giant aquifers—ancient relicts that took many thousands of years to form—that has watered cities and exploded lawns across deserts from Texas to Saudi Arabia.

The problem is that no one knew or cared where the groundwater came from. In the early days many drillers thought it was infinite, or replenished somehow by mysterious underground rivers. But because aquifers are ultimately recharged by whatever rainfall manages to percolate down from the surface, they refill slowly. If water is pumped out faster than new water can ooze in, the aquifer goes into overdraft. The water table drops and wells fail. Farmers drill deeper, then the wells fail again. Eventually the aquifer is depleted or lowered too far to raise, and becomes uneconomic.

We are now coming to appreciate just how widespread this problem is globally, by measuring small variations in the Earth’s gravity field precisely from space. In 2009 researchers using the NASA Gravity Recovery and Climate Experiment (GRACE) satellites discovered that despite natural recharge, groundwater tables in heavily irrigated parts of the Indian subcontinent are falling between four and ten centimeters per year, an unsustainable decline in an area supporting some six hundred million people.²³²

Most irreversible is groundwater overdrafting in our driest places. Not only do these aquifers have very low rates of rainfall recharge—and thus faster overdraft—but they are very often the main or only water source upon which people depend. Once gone, they take thousands of years to refill, or may never refill at all because they are relicts left over from the end of the last ice age. For all intents and purposes fossil groundwater, like oil, is a finite, nonrenewable resource. Eventually, the wells must run dry.

Death of a Giant

The Ogallala is a monster aquifer underlying no fewer than eight states across the western United States.²³³ Its existence had been known to High Plains ranchers and dryland farmers since the 1800s, but it wasn’t until the 1940s—with the arrival of modern pumps powered by electricity or natural gas—that the spigot could be opened wide. Since then, we have been pumping seven trillion gallons of cold, clear water out of the Ogallala Aquifer to irrigate circular center-pivot fields of wheat, cotton, corn, and sorghum across the Great Plains. This soon transformed over one hundred million acres of highly marginal land— much of it abandoned after the 1937 Dust Bowl—into one of the world’s most productive agricultural regions. From your airplane window or a Web-browser view from Google Earth, you can see for yourself the green circles stamped out across the Texas and Oklahoma panhandles through eastern Colorado, New Mexico, and Wyoming; and running north through Kansas and Nebraska all the way to southern South Dakota. Those verdant, neatly aligned disks are the telltale fingerprints of the Ogallala Aquifer.

Zoom in with your Web browser and you’ll see many of the disks are brown. By 1980 it was common knowledge that wells were falling fast in the Ogallala’s southern half. By 2005 large portions had fallen by 50 feet, 100 feet, even 150 feet, in southwestern Kansas, Oklahoma, and Texas. Wells in the wetter northern half were holding up fine thanks to much higher natural recharge rates, but the dry southern states, where the Ogallala water is mostly of Pleistocene age,²³⁴ was in serious overdraft. Wells began sputtering. Texas farmers, accustomed to feeding one or more center-pivot fields from a single well, began drilling several wells to support a single field.

In 2009 a team led by Kevin Mulligan, a professor of economics and geography at Texas Tech, completed a detailed study of just how fast Texas farmers are emptying out the southern Ogallala. Using a Geographic Information System (GIS), his team mapped thousands of wells throughout a forty-two-county area of northern Texas. They used the wells’ water-level and flow-rate data to calculate the remaining saturated thickness of the Ogallala, and how fast the water table is falling. From these data they constructed a series of maps projecting the remaining useful life expectancy of the aquifer, for ten, fifteen, and twenty-five years into the future.

The results were shocking. Texas’ Ogallala Aquifer is dropping an average of one foot per year and in some places as much as three feet per year. Many areas are careening toward a saturated thickness of just thirty feet, at which point the last wells will begin to suck air.²³⁵ These maps are incredibly precise—all of the thousands of individual wells and the green crop circles they support are shown—so the impending demise of the aquifer is mapped out in a very detailed way. Texas’ Parmo and Castro counties are plastered with center-pivot crops today, but their lush surface belies the situation below. Both counties are facing the abandonment of irrigated agriculture within the next twenty-five years.

Might the southern Ogallala be saved by sound conservation measures, like converting to drip irrigation? “We don’t see it,” snorted Mulligan to my question. It sounds great in theory, but his well data show that in practice, converting center pivots from sprinklers to dripping hoses doesn’t slow the speed of the Ogallala’s depletion. Instead, farmers just run their new drip systems longer so as to pull out the same volume of water, resulting in the same net drawdown. The hard fact is that there just isn’t any way to save an aquifer whose natural recharge is one-half to one inch per year, when it is being drawn down a foot or more per year. Ironically, the single biggest benefit of drip irrigation to farmers isn’t delaying the Ogallala’s death but ensuring it, by allowing access to its last remaining dregs.²³⁶ These wells are the final straws into a doomed giant once thought to be invincible.

Oil and Water Truly Don’t Mix

Everyone knows that it takes water to get food. Less obvious is how much energy it takes to get water (for pumping, moving, purifying, and so on). And hardly anyone grasps how much water is needed to get energy. But like hopeless lovers, water and energy are inextricably intertwined. Pressure on water resources, therefore, is intimately linked to pressures on coal, oil, and natural gas resources. Except for wind and certain forms of solar