In the first study of its kind, Martin Pasqualetti, a professor in the School of Geographical Sciences and Urban Planning at Arizona State University,239 scrutinized how much water consumption (i.e., evaporation) Arizona’s different energy technologies require in order to produce one megawatt-hour of electricity. What he found may surprise you:
Water Losses Embedded in Arizona Electricity Generation
From Pasqualetti’s data we learn that the water consumption of energy production is not only large, but varies tremendously depending on the type of energy being used. For example, a nuclear power plant evaporates about 785 gallons of water to generate one megawatt-hour of electricity, whereas natural gas power plants evaporate considerably less (especially modern combined-cycle plants, which evaporate about 195 gallons per megawatt-hour). This means that an average house in Phoenix, using twenty megawatt-hours per year, will unknowingly evaporate nearly 16,000 gallons of water if its electricity comes from a nuclear power plant, but only about 3,900 gallons if it comes from a combined-cycle natural gas plant. More virtual water.
To put that number into perspective, 15,000 gallons is roughly what a typical Phoenix household with irrigated landscaping uses in two weeks. So this “embedded” water is not an enormous amount, but still significant in such a dry place. But the big surprise here is that in terms of electricity generation, hydropower, of all things, is the worst water waster,240 followed by concentrated solar thermal (CSP) technology, then nuclear. Arizona does not grow biofuel crops, but other studies show biofuels are even worse than hydro in terms of water consumption.241 Thus biofuels, hydropower, and nuclear energy, while hailed for being carbon-neutral (or nearly so), are worse even than coal when it comes to water consumption. Of the renewables, only wind and solar photovoltaics are truly benign—something, Pasqualetti points out, that would make solar photovoltaics more cost-competitive if the price of the saved water was taken into account.
The water-energy nexus works both ways. Examined in the opposite direction, energy is needed at every step along the way to deliver clean water to a house. Take again, for example, our typical Phoenix home, which consumes about an acre-foot of water per year. It requires two megawatt-hours of electricity—roughly 10% of the home’s total energy use—to pump that acre-foot uphill from the Colorado River some two hundred miles away, purify it, and pressurize it locally. But those megawatt-hours never appear on any electric bill; they are embedded within the water bill itself. Remarkably, almost all the cost of providing drinking water to Phoenix households is for the energy embodied within it, not for the water.
“Indeed,” says Pasqualetti, “water and energy are married to one another. Water is needed in electrical generating stations if they are to run efficiently. Energy, on the other hand, is needed to provide our houses with safe drinking water. How much of each commodity is needed to provide the other is something not well appreciated by the public.”242
It is something not well appreciated by politicians and planners either. Instead of recognizing this marriage between energy and water, their respective planning and regulatory agencies are almost always totally separate entities. “Energy analysts have typically ignored the water requirements of their proposed measures to meet stated energy security goals. Water analysts have typically ignored the energy requirements to meet stated water goals,” concluded a recent Oak Ridge National Laboratory report.243 Historically we have gotten away with this thanks to cheap water, cheap energy, or both. That cushion will continue to narrow as supplies of both tighten out to 2050.
One of the most widely anticipated outcomes of climate change is that the Hadley Cell circulation will weaken slightly and expand. This appears not only in a broad range of climate model projections for the future, but also from historical data extending three decades into the past.244 The effect of this is the spawning of more clouds and rain in the tropics, but even drier conditions and a poleward expansion of the two desert blast zones straddling both hips of the equator. Precipitation futures are notoriously difficult to project, but this is one of those things about which all the climate models agree. Put simply, many of the world’s wet places will become even wetter, and its dry places even drier.
Rainfall will increase around the equator, but decrease across the Mediterranean, Middle East, southwestern North America, and other dry zones. Rivers will run fuller in some places and lower in others. One highly regarded assessment tells us to get ready for 10%-40% runoff increases in eastern equatorial Africa, South America’s La Plata Basin, and high-latitude North America and Eurasia, but 10%-30% runoff declines in southern Africa, southern Europe, the Middle East, and western North America by the year 2050.245 Through the language of statistics, these models are telling us to brace for more floods and droughts like the ones in Iowa and California.
The Great Twenty-first-Century Drought?
Part of the explanation for the many floods and droughts that happened around the world in 2008 was that it was a La Niña year, meaning that sea surface temperatures (SSTs) in the eastern half of the tropical Pacific Ocean cooled off. This triggered, among other things, dry conditions over California, contributing to its ongoing drought (her counterpart, El Niño, is associated with warm SSTs and wetter conditions there). Through connections between the sloshing ocean and the atmosphere, this “Little Girl” had impacts on human water supply that reverberated worldwide.
My UCLA colleague Glen MacDonald, an expert in the study of prehistoric climate change, is deeply concerned that something like the 2008 La Niña could happen again—but persisting for decades rather than months. In fact, MacDonald and his students believe the American Southwest, in particular, could be struck by a drought worse than anything ever seen in modern times. From shrunken tree-rings and other prehistoric natural archives, they have assembled a growing body of evidence that the region suffered at least two extended “Perfect Droughts” (coined by MacDonald to describe periods when Southern California, northern California, and the upper Colorado River Basin all experienced drought simultaneously) during medieval times.246 These Perfect Droughts were as bad as or worse than the Dust Bowl but lasted much longer, persisting as long as five to seven decades (the Dust Bowl lasted barely one). These prehistoric data tell us that this heavily populated region is capable of experiencing droughts far worse than anything experienced since the first European explorers arrived.
One reason for these massive prehistoric droughts was that between seven hundred and nine hundred years ago temperatures rose. The increase was similar to what we are beginning to see now but not so high as what climate models are projecting by 2050. The reason for the medieval temperature rise (fewer volcanic eruptions plus higher solar brightness) was different from what’s happening today, but it nonetheless provides us with a glimpse of how our planet might respond to greenhouse warming.247
Not only did the medieval climate warming increase the drying of soils directly, it may also have altered an important circulation pattern in the Pacific Ocean, by shifting relatively cool water masses off the western coast of North America for many decades at a time (this would be a prolonged negative phase of the so-called “Pacific Decadal Oscillation,” an El Niño- like oscillation in the northern Pacific that currently vacillates over a 20-30-year time scale). This likely created pressure systems driving rain-bearing storm tracks north, rather than south, across the western United States, triggering drought conditions in the American Southwest. Should the projected rise in air temperatures cause the Pacific circulation to behave like this again, the prolonged medieval megadroughts could return. Similar connections between shifting sea-surface temperatures and geographic rainfall patterns over land exist for the Atlantic and Indian oceans as well.
MacDonald points out that by the time Schwarzenegger declared a state of emergency in 2009, most of the southwestern United States was actually in its eighth year of drought, not third. “Arguably, we are now into the great Twenty-first Century Drought in western North America,” he mus
ed to me. “Could we be in transition to a new climate state? Absolutely. Should we be worried? Absolutely.” His concerns are echoed by Richard Seager at Columbia University’s Lamont-Doherty Earth Observatory. In a widely read Science article,248 Seager and his colleagues showed consensus among sixteen climate models that projected greenhouse warming will drive the American Southwest toward a serious and sustained baking. Their result, of course, is dependent on the group of models analyzed, and the simulation is imperfect because today’s coarse-scale climate models don’t represent mountainous areas very well (e.g., the Rockies, which produce most of the region’s snowpack water). But if these model projections prove correct, then the drought conditions associated with the brief American Dust Bowl could conceivably become the region’s new climate within years to decades.
Risky Business
“Stationarity Is Dead,” announced another Science article in 2008, sending a cold shiver through the hearts of actuaries around the world.249 A hydrology dream team of Chris Milly, Bob Hirsch, Dennis Lettenmaier, Julio Betancourt, and others had just told them that the most fundamental assumption of their job description—reliable statistics—was starting to come apart.
Stationarity—the notion that natural phenomena fluctuate within a fixed envelope of uncertainty—is a bedrock principle of risk assessment. Stationarity makes the insurance industry work. It informs the engineering of our bridges, skyscrapers, and other critical infrastructure. It guides the planning and building codes in places prone to fires, flooding, hurricanes, and earthquakes.
Take river floods, for example. By continuously measuring water levels in a river for, say, twenty years, we can then use the stationarity assumption to calculate the statistical probability of rarer events, e.g., the “fifty-year flood,” “hundred-year flood,” “five-hundred-year flood,” and so on. This practice, while creating enormous misunderstanding with the public,250 has also made us safer. Hard statistics, rather than the whims of developers or mayors, are used to design bridges and for zoning. But flood prediction, and most other forms of natural-hazard risk assessment, rest on the core assumption that the statistics of past behavior will also apply in the future. That’s stationarity. Without it, all those risk calculations go straight out the window.
A growing body of research is showing that our old statistics are starting to break down. Climate change is not the sole culprit. Urbanization, changing agricultural practices, and quasi-regular climate oscillations like El Niño all influence the statistical probabilities of flooding. However, the dream team’s paper and others like it251 tell us that climate change is fundamentally altering the statistics of extreme floods and droughts, two things of enormous importance to humans. “In view of the magnitude and ubiquity of the hydroclimatic change apparently now under way,” they wrote, “we assert that stationarity is dead and should no longer serve as a central, default assumption in water-resource risk assessment and planning. Finding a suitable successor is crucial for human adaptation to changing climate.”252
Unfortunately, we have no good replacement for stationary statistics yet, certainly nothing that works as well as they once did. Moreover, there has been hardly any basic research done in this area since the 1970s. We can’t just invent a completely new branch of mathematics and train a new generation of water experts in it overnight. “Water resources research has been allowed to slide into oblivion over the past thirty years,” Lettenmaier growled later in a separate editorial. “Certainly the profession has been slow to acknowledge these changes and acknowledge that fundamentally new approaches will be required to address them.”253 So even as we’re beginning to grasp the enormity of this problem, we presently have no clear replacement for our old way of doing things. Until we find one, risks will be harder to predict and to price. We can expect insurance companies to react accordingly. In 2010, after failing to win a nearly 50% rate increase from state regulators, Florida’s largest insurance company abruptly canceled 125,000 homeowner policies in the state’s hurricane-prone coastal regions, saying the recent series of devastating hurricanes had rendered its business model unworkable. 254 Get ready for higher premiums, uninsurable properties, and failed or overbuilt bridges.
Nonreturnable Containers
Changing drought and flood statistics are not the only way that rising greenhouse gases harm our water supply. All of our reservoirs, holding tanks, ponds, and other storage containers are trifling compared to the capacity of snowpacks and glaciers. These are free-of-charge water storehouses, and humanity depends upon them mightily.
Snow and ice hoard huge amounts of freshwater on land, then release it in perfect time for the growing season. They do this by bulking up in winter, then melting back in spring and summer. They are the world’s hugest water-management system and, unlike a dam reservoir, displace no one and cost nothing. Glaciers (and permanent, year-round snowpacks) are especially valuable because they outlast the summer. This means they can hoard extra water in cool, wet summers, but give it back in hot, dry summers, by melting deeply into previous years’ accumulations. Put simply, glaciers sock away water in good years when farmers need it least, and release water in bad years when farmers need it most. Glaciologists call these “positive mass-balance” and “negative mass-balance” years, respectively, and they are a gift to humanity. Glaciers keep the rivers full when all else is dry. They are the ultimate sunny-day fund.
If you read the news, then you already know that many of the world’s glaciers are beating a hasty retreat, whether through warmer temperatures, less precipitation, or both. Ohio State University’s glaciologist power-couple Lonnie Thompson and Ellen Mosley-Thompson have been photographing the deaths of their various study glaciers since the 1970s. Some of these are even wasting away at their summits, which is a death knell for a glacier. There are ski resorts in the Alps trying to save theirs by covering them with reflective blankets. Most glaciologists expect that by 2030, Montana’s Glacier National Park will have no glaciers left at all.
Seasonal snowpack, which does not survive the summer, cannot carry forward water storage from year to year like glaciers do, but it is also a critically important storage container. It creates a badly needed time-delay, releasing water when farmers need it the most. By holding back winter precipitation in the form of snow, the retained water flows downstream to farmers later, in the heat of the growing season. Without this huge, free storage container, this water would run off uselessly to the ocean in winter, long before growing season. Rising air temperatures harm this benefit, both by increasing the prevalence of winter rain (which is not retained) and by shifting the melt season to earlier in the spring. Because the growing season is determined not only by temperature but also the length of daylight, farmers are not necessarily able to adapt by planting sooner. By late summer, when the water is needed most, the snowpack is long gone.
This seasonal shift to earlier snowmelt runoff portends big problems for the North American West and other places that rely on winter snowpack to sustain agriculture through long, dry summers. California’s Central Valley—the biggest agricultural producer in the United States—depends heavily on Sierra snowmelt, for example. But the long-term projection for health of the western U.S. snowpack is not good. It has already diminished in spring, despite overall increases in winter precipitation, in many places.255 By late 2008, Tim Barnett at the Scripps Institute of Oceanography and eleven other scientists had definitively linked this phenomenon to human-caused climate warming. This is not good news, they wrote in Science, warning of “a coming crisis in water supply for the western United States” and “water shortages, lack of storage capability to meet seasonally changing river flow, transfers of water from agriculture to urban uses, and other critical impacts.”256
High-profile research like this does not go unnoticed by policy makers. One response is to build more reservoirs, canals, and other engineering schemes to store and move water. China is now planning fifty-nine new reservoirs in its western Xinjiang province to ret
ain water from glacier-fed rivers. In 2009, U.S. Interior Secretary Ken Salazar announced $1 billion in new water projects across the American West, with over a quarter-billion going to California alone.257
Thus begins our new technological race—to adapt to a shrinking water storage capacity, once provided for free by snow and ice. But it is important to understand that no amount of engineering can replace that storage. Think back to I. A. Shiklomanov (p. 86), his huge container of ice, and trifling container of surface water. Even if we quadrupled the world’s reservoirs, they wouldn’t come remotely close to replacement. And even if they did, we’d still end up with less water: Unlike snow and ice, water evaporates like crazy from open reservoirs.
We can’t hold it all back. More of the world’s water is leaving the mountains to run to the sea.
Into the Sea
It’s abnormal to be thinking about melting glaciers when standing on a nice sunny beach during holiday break. But this was no ordinary beach and no ordinary holiday. It was Christmas 2005, and I and other members of the Smith family were staring dumbly at the bones of what had once been my aunt and uncle’s house, a dozen blocks inland from the Mississippi coast. With the ease of a kid blowing foam across a cup of hot chocolate, Hurricane Katrina had thrown a wall of water—a storm surge—right through their lovely Biloxi neighborhood.
The place was a deserted war zone. Houses smashed to splinters, cars crushed and tossed into swimming pools. Nearer the beach, there were no house bones at all, just smooth rectangles of white concrete, scrubbed and gleaming to show where million-dollar homes had once stood. It was four months since the hurricane but the place was abandoned. No one was hauling away debris, no sound of hammering nails. All was silent except for the songbirds, cheeping and squabbling amid the wreckage. To them it was just another beautiful day on the American Gulf Coast.
The World in 2050: Four Forces Shaping Civilization's Northern Future Page 13