THE KEY UNDERLYING DEMOGRAPHIC trend that can strain the energy-water nexus is growth: population growth and economic growth. Population is growing, exceeding 7 billion people globally in 2011, and is projected to continue growing. Peter Gleick, a leading scholar on water issues, MacArthur Fellow, and member of the National Academy of Sciences, made a comment about global population that really stuck with me. While briefing the Roundtable on Sustainability at the National Academy of Sciences meeting in June 2013, he discussed global population trends. He said, “The most interesting day in the history of the world will happen in the twenty-first century: that is the day the global population is smaller than it was the day before.” Until that day, global population is projected to keep growing, plateauing between 9 and 11 billion people sometime between 2050 and 2100.
Along the way, each one of those billions of people will need energy and water. More people means more demand. At the same time we have been getting richer. Demand for energy and water have been growing faster than population, driven by economic growth on top of the population growth.1 This phenomenon occurs because affluent people eat more meat, which leads to water consumption. They also consume more electricity, which uses water. Unfortunately, many water withdrawals are from nonrenewable resources. That means the trends for consumption will trigger water shortages unless something changes. By 2005, at least half of Saudi Arabia’s fossil (nonrenewable) water reserves had been consumed in the previous two decades. Globally, much more groundwater is pumped out of aquifers than is recharged naturally. Therefore the water table has been going down.
It’s not just the Middle East, though. Significant declines have also been observed in the Ogallala Aquifer under the Great Plains of the United States, spanning eight states from South Dakota to Texas.2 Water tables lowered by as much as 234 feet were observed in Texas, while the average drop across the entire aquifer was 14 feet. Storage of water fell from 3.2 billion to 2.9 billion acre-feet. Although these numbers are daunting, the impacts on water in the aquifer were not exclusively negative in all locations. Some localized increases up to 84 feet were observed in Nebraska as a consequence of seepages and reservoirs affecting the amount of water stored underground.
These withdrawals from nonrenewable sources and shifts in water levels, stored water, and water use over time affect the amount of water that is available to humanity and nature. Overall, water availability is declining globally.3 Available water dropped from 17,000 cubic meters per person in 1950 to 7,000 cubic meters per person in 2000. Water stress occurs between 1,000 and 1,700 cubic meters, and a water crisis occurs at less than 1,000 cubic meters. Notably, some countries are already at these levels, and are cause for concern: Qatar (91), Libya (111), Israel (389), and the UK (1,222). All of these datasets point toward a conclusion that water stress is increasing. High-profile research published in Nature has concluded that nearly 80 percent of the global population endures high levels of threat to water security.
Perhaps one of the most impressive signs of overpumping is that we are actually causing the oceans to rise in a nontrivial and measurable way.4 Scientists have found that a variety of water-use factors have caused the sea level to rise 0.7 millimeters per year between 1961 and 2003, which is about 42 percent of the observed total sea-level rise. These factors include overuse of groundwater, artificial reservoir water impoundment, and climatedriven changes in terrestrial water storage. Of the 1.8 millimeters per year of total sea-level rise from 1963 to 2003, climate change caused 1.1 millimeters of the rise, through heating of the oceans, which caused thermal expansion, and melting snowcaps and glaciers, which caused additional runoff of freshwater into the oceans, raising sea levels. Land-based groundwater extraction with subsequent runoff was responsible for the other 0.7 millimeters, a substantial portion.
Climate change is likely to exacerbate strains at the energy-water nexus. The way climate change manifests itself is through changes to the hydrologic cycle. “Climate change” might be better named as “water change.” And those changes show up in a variety of ways, such as elevated ocean levels, elevated ocean temperatures, more frequent and intensive flooding, more frequent and intensive droughts, and distorted snowmelt patterns.
These shifts can have a significant impact on civilization, because our societies have built themselves in particular locations and with specific configurations based on expectations built over centuries for where the water will be. Where and how much water is available at which time of year has been a driving force for the industrial mix, agricultural choices, and many other societal elements that we take for granted today. Most societies configured themselves with an expectation that water availability would stay the same, making themselves vulnerable to sudden, dramatic changes. These vulnerabilities mean that society can actually collapse in the face of extended changes to the availability of water.
Elevated ocean levels are a direct threat to the 40 percent of the world’s population that lives within about sixty miles of the coastline. Higher ocean levels raise the risk for erosion of coastlines, submersion of valuable properties and infrastructure, and saltwater intrusion into freshwater aquifers. All of these are expensive to mitigate. Elevated ocean temperatures have ecosystem impacts that might be bad for fisheries, aquaculture, and power plant cooling. More frequent and intensive flooding is difficult for societies to manage for obvious reasons. Floods are hard to control and can do a lot of damage. More floods mean more cumulative damage, and greater intensity means each individual flood is likely to be more damaging or sudden than usual. It will cost a significant amount of money to move buildings out of expanded flood plains or shore up levees, protect land that can absorb the water, or build reservoirs that are intended to stay empty and only used for capturing excess water during flooding.
On the flipside, more frequent and intensive droughts will be the ironic partner to the floods. Mitigating droughts requires expensive infrastructure for storing water, long-haul pipelines to move the water farther, more powerful pumps for raising water from ever deeper wells as surface water sources dry up and overextraction from nonrenewable groundwater sources increases.
Distorted snowmelt patterns will be another consequence of climate change. The snowpack may be thinner and melt earlier, affecting the rhythms of water availability, irrigation, crop rotation, and other patterns that have built up over centuries. Of the world’s 7 billion people, approximately 1.5 billion rely on snowmelt from the Himalayas alone. Add in those living on snowmelt from the Rockies, Andes, and other major mountain ranges, and the tally will grow. The villages around Kilimanjaro have been flagged as particularly vulnerable. On May 29, 2015, the snowpack in California was officially reported to be zero, meaning the source of water for tens of millions of people and the vast preponderance of national fruit, nut, and vegetable cultivation was at risk.5 Managing these shifting patterns might spawn impactful, expensive, and energy-intensive investments in large-scale water storage infrastructure such as reservoirs to hold the water over a greater span of time.
All of these outcomes can be mitigated in one way or another, either through investments in new infrastructure, changing industrial and agricultural mixes of the societies involved, or by picking up and moving to another location that will have better odds in the climate change sweepstakes. All of these options represent hard choices. And some of those choices, because of their energy requirements, might exacerbate the situation in the long term. At the same time, these options often fall hardest on the poorest societies. That means the emissions from the richest members of the globe will cause expensive problems for the poorest. The moral challenge of this situation is difficult to swallow. The inequality in the emissions (mostly by the rich), and the suffering (mostly by the poor) presents a key quandary for the world to resolve.
Unfortunately, the energy-water-climate nexus has a positive feedback loop. Our energy consumption causes climate change, which changes the hydrologic cycle, triggering investments in energy-intensive water solutions, which exacerbates climate change, and so forth. Frustratingly, the higher temperatures of a warming planet reduce the global photosynthetic efficiency. That means we will use more energy-intensive irrigation, fertilizing, and harvesting with energy inputs to overcome the hit on efficiency.
Energy, water, and climate have a positive feedback loop. Our energy sector contributes to anthropogenic climate change, which changes the water cycle, which causes us to use more energy to solve our water problems, which contributes to climate change, and so forth. [Image idea courtesy of Jane Long]
Climate change may also reduce the amount of energy we get from emissions-free hydropower. In the United States, more than half of the nation’s hydroelectric generation occurs in California, Oregon, and Washington. This region is also particularly sensitive to climate change: as the climate warms up, the snowmelt and precipitation patterns become distorted in ways that are detrimental. And, the cumulative impact of the changes is nonlinear and magnified. For a large basin like that of the Colorado River, small declines in precipitation cause major droughts, which in turn can dramatically reduce power output from a whole chain of hydroelectric dams. Every 1 percent decrease in precipitation causes a 2–3 percent drop in streamflow, and every 1 percent decrease in streamflow in the Colorado River Basin yields a 3 percent drop in power generation.6 At the same time, many millions of people depend on that basin’s water for irrigation, drinking, commercial activity, industrial processes, and, of course, for power production. And the outlook for precipitation may get worse. Higher temperatures also mean that there will be additional evaporation, reducing water stored in reservoirs. The reduced hydropower in California during the multiyear drought from 2011 to 2015 caused electric rates to increase: as hydropower dropped from 18 percent to 12 percent of the fuel mix, utilities spent extra money purchasing natural gas to make up the difference.7 There is a silver lining, which is that hydropower could initially increase because of higher-than-normal snowmelt.8
Beyond the trends for increasing demand for total consumption of water and energy, we are moving toward more water-intensive energy. That trend is especially true for transportation fuels, where for national security, environmental, and economic reasons there is a strong desire in the United States to move away from petroleum. The preferred alternatives are domestic, low-carbon, and sustainable fuels. For many people, especially the agricultural sector, that means corn-based ethanol. But it could also mean natural gas, methanol, or electricity.
The challenge is that many of those fuels are more water intensive than conventional petroleum-based fuels such as gasoline and diesel.9 Because biofuels require so much water, the federal push for more biofuels with the RFS (Renewable Fuels Standard, which requires that a certain volume of biofuels are consumed annually) has essentially become a mandated increase in water consumption for transportation fuels. The push for electric vehicles also has the unintended consequence of increased water use for power plant cooling. The RFS and incentives for electric vehicles are classic examples of energy policymaking on one hand that ignores the water consequences on the other hand. Adding up the biofuels volumes that are mandated will cause significant increases in water needs. In 2005, petroleum-based gasoline required about 250 billion gallons of water to produce 140 billion gallons of fuel. Switching to ethanol from corn—with just 15 percent of the crop requiring irrigation—means we will need well over a trillion gallons of water per year within two decades.10 Just a small irrigated fraction of the biofuels mandate will cause water consumption for light-duty transportation fuels to go up by a factor of four or more. Just imagine how bad it would be if all the corn we grow required irrigation.
Adding in the expectations for other fuels such as cellulosic ethanol, coal-to-liquids, and other sources adds in yet another trillion gallons of water consumption. Keeping in mind that the nominal annual water consumption in the United States is about 36 trillion gallons, this 2-plus trillion gallons per year of additional water consumption is significant. It moves transportation into a category as one of the largest water consumers in the nation. As a nation we prefer enriching midwestern farmers instead of Middle East autocrats, which is an admirable goal. However, the water impacts of doing so with the RFS are significant; essentially we are switching from foreign oil to domestic water. Before embarking on such an ambitious mission, maybe we should check first to make sure we have the water. The story is similar in other parts of the world that are trying to displace conventional petroleum with thirstier options.
Similar to the trend of moving toward more water-intensive energy, we are also moving toward more energy-intensive water. This shift has several different components, including stricter water/wastewater treatment standards, deeper aquifer production, long-haul pipelines, and desalination. Each of those elements is more energy intensive than conventional piped water today, and seems to be a more common option moving forward. The market trend for bottled water could also be considered one of those energy-intensive options.
As societies become wealthier, their concerns shift from focusing on economic growth to protecting the environment. This phenomenon is described by movement along the environmental Kuznets curve. In the United States, we went through a similar trajectory. The first hundred years after the second Industrial Revolution saw significant increases in energy consumption. Then, since the 1960s, environmental protections have become more important, yielding several pieces of landmark environmental legislation in the early 1970s: the Clean Water Act, Clean Air Act, Endangered Species Act, and creation of the Environmental Protection Agency. Many other prominent pieces of environmental rules have since been implemented.
Protecting drinking water quality from the output of water treatment plants for the sake of public health and discharge water quality from wastewater treatment plants for the sake of ecosystems are two important pieces of that trend. But water and wastewater treatment require nontrivial amounts of energy. Furthermore, advanced treatment methods to meet stricter standards are more energy intensive than treatment for lower standards. For example, advanced treatment systems for wastewater with nitrification require about twice as much energy as trickling filter systems. As we tighten the standards for water and wastewater treatment, we are essentially edging toward increases in energy consumption. While new treatment technologies and methods become more efficient over time after their initial implementation, the standards tighten in parallel. How these balance out is unclear.
At the same time, the water coming into water and wastewater treatment plants is getting more polluted with time. As population grows, there are more discharges into the waterways. Those discharges contain constituents that weren’t always there in such high concentrations. For example, there have been growing concerns about pharmaceuticals (including birth control pills and pain pills) in sewage streams, which are difficult for wastewater treatment plants to remove. Doing so requires new equipment and ongoing investments of energy.11
In an ironic example of the energy-water nexus, some of our energy choices create water quality impacts that require additional energy to treat. For example, increased biofuels production from corn in the middle part of the United States is expected to cause additional runoff of nitrogen-based fertilizers and other pollution. Subsequently, we will need more energy to remove that pollution.12 And many domestic users of water rely on their own personal wells to access untreated, clean, groundwater. If pollution infiltrates the groundwater, as has happened in the corn belt, users might need to add treatment systems, increasing their energy bills for their water.
The wastewater streams from hydraulic fracturing of shales to produce oil and gas contain much higher levels of total dissolved solids than most wastewater treatment plants can handle while complying with discharge standards.13 That means more energy has to be spent in one of several ways: on trucking that wastewater to disposal sites or specialized industrial wastewater treatment facilities that might be far away (something that happens rarely), for on-site treatment to recycle and reuse the water in subsequent wells, or on new equipment at the wastewater treatment plant to treat those streams. Even that new equipment is sure to require energy.
We are also contemplating moving water farther from its source to end-use. Long-haul pipelines and interbasin transfer, which is moving water from one river basin to another, are common proposals to solve the crisis of declining local water supplies. While the idea of aqueducts has been around for thousands of years, the scale, length, and volumes of water that are moved are growing. Some of the classic water transfer systems include the State Water Project in California described earlier. California’s system is the state’s largest electricity user because it must pump the water over mountains, though it also captures a lot of energy when the water flows back downhill through inline hydroelectric turbines coupled with chutes.
In addition to the California system, the island of Maui has an incredible handcut series of water channels that circle its two volcanoes, moving water miles from the wet portion of the island—one of the wettest places in the United States—to the dry inland plains where farming occurs. This system operates by gravity, and also generates electricity along the way.
Moving forward, as water tables fall and surface sources dry up, municipalities are more likely to consider the cost of expensive and far-flung water-gathering systems that pull water to a city from deeper in the ground or farther away. These long-haul systems will generally not be gravity-fed, and will require a lot of energy. Plus, they will incur ecosystem impacts as water from one basin is moved to another. While that might be good in terms of supplementing the flow for the receiving basin, it is bad for the basin that loses the flow. Plus, there is the concern of invasive species moving along with the water.
Perhaps the most ambitious project is the South–North Transfer Project in China (also known as the South–North Water Diversion Project, or SNWD). This project essentially aims to move major southern rivers—the Yangtze and Han—across the country to the Yellow and Hai Rivers. The industrialized north is relatively water poor, whereas the southern part of China is relatively water rich. The scale, scope, and ambition of the project is reminiscent of U.S. water planners who have dreamed for decades of diverting the Yukon River in Alaska or the Missouri River to the Southwest so that the deserts would bloom with flowers and fruit trees. Peter Gleick refers to these as “zombie water projects” because no matter how expensive or silly, the ideas just will not die.14
The total estimated flow for the Chinese endeavor is projected to divert 44.8 billion cubic meters per year from the south more than a thousand miles to the north, at a total cost estimated to be $62 billion.15 Not to be left out, India is also building its own long-haul water pipeline. And, joining the pack, Texas is, too.16 For example, in Texas, a 240-mile pipeline is being built to bring 370,000 cubic meters per day of water from Lake Palestine to the Dallas–Fort Worth metroplex. The total capital cost for the construction is estimated to be $888 million, or $3.7 million per mile of pipeline. The annual electricity consumption is expected to be $11.3 million, or $0.71 per cubic meter.
In addition, there is a water pipeline that oil and gas tycoon T. Boone Pickens proposed in early 2008 with the expectation that water would be the new oil.17 The pipeline would move water from Roberts County in the panhandle of Texas toward the Dallas–Fort Worth metroplex. This project was controversial for a variety of reasons, one of which is that the water rights Pickens holds are for fossil water in the Ogallala aquifer, which can take millions of years to recharge. And by sending it to Dallas, it seems one of its likely applications will be for watering lawns. While some energy would be used for pumping the water out of the aquifer, once it is at the surface, it would mostly use gravity for its downhill trip to Dallas. Ultimately the deal was scuttled because of the $3 billion price tag for the pipeline. Instead, Pickens sold the water rights to local thirsty cities.18
Another of the key trends to watch is how many municipalities are turning to desalination as a solution for water supply issues. Some people have called this “a river flowing back from the sea.” Traditionally, rivers flow from freshwater sources to saltwater destinations, picking up salts and other minerals along the way. In fact, the oceans were once fresh, but became salty over many eons of runoff from lands. Desalination reverses this trend, as the saltwater sources become freshwater at their destination.
In 2013, over 17,000 desalination plants were already installed worldwide, providing approximately 21 billion gallons per day (67 million cubic meters per day) of freshwater.19 With a blistering pace of growth, that capacity is projected to keep expanding quickly. More than three-fourths of new capacity will be for desalinating seawater, with the rest from brackish groundwater or salty rivers. While thermal desalination (using heat) represents about 25 percent of the installed capacity by 2010, it represents a shrinking share of new installations as builders seek the less energyintensive reverse osmosis membrane-based system. Even with the lower energy approach, desalination is still an order of magnitude more energy intensive than traditional freshwater treatment and distribution. Desalination is capital intensive, too: the annual global desalination market exceeds $10 billion.
Growth is particularly rapid in energy-rich, water-poor parts of the world, such as the Middle East, northern Africa, and Australia. After a severe drought that lasted several years, water-strapped Israel famously turned to the sea for its water, rapidly building a handful of desalination plants to produce about 200 billion gallons of freshwater annually by desalting water from the Mediterranean.20 Rapid growth is also occurring in China, where booming industrial activity is straining water supplies that serve the world’s largest population. It is also popping up in locations such as London and the United States, where the abundance of water is very different than in the arid regions of the world. As noted earlier, London’s desalination plant was very controversial, and became a big part of several mayoral campaigns.
Despite its relative water wealth, the United States is the world’s second-largest market for desalination, trailing only Saudi Arabia.21 This phenomenon is partly the result of the unequal distribution of water resources across the United States. And, as a wealthy country, the water consumption per capita is quite high and the money to finance large-scale infrastructure projects is available. Projects are under consideration for seawater reverse osmosis in coastal states such as California, Texas, and Florida. And brackish water projects are under development to serve inland communities that sit atop large brackish aquifers, as in Texas, Arizona, and New Mexico.
The two most energy-intensive options—desalination and long-haul transfer—can also be combined to create an even larger energy requirement for water.22 Natural water flows occur by gravity, but for seawater desalination, the opposite is true. By definition, coastal waters are at sea level, so moving the water inland requires pumping water uphill. One such desalination project under development in the United States is a coastal facility along the Gulf of Mexico that is designed to provide freshwater for San Antonio, Texas. That means the water would be moved nearly 150 miles inland, increasing in elevation nearly 775 feet.
While trading energy for water makes a lot of sense in places like the Middle East or Libya, where there is an abundance of energy and a scarcity of freshwater, that tradeoff is not obviously a good value in places like the United Kingdom or the United States, where other cost-effective options such as water conservation, graywater capture, and water reuse might be available.