Trends at the energy-water nexus
Trends at the energy-water nexus
The following is an excerpt from the "Trends" chapter of "Thirst for Power."
“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.
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.
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.
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 diff erence.
There is a silver lining, which is that hydropower could initially increase because of higher-than-normal snowmelt.
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 petroleumbased fuels such as gasoline and diesel. 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.
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.
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.
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.