In 2014, as California was in the midst of one of the worst droughts in its recorded history, Julia Szinai was working for an electric utility. The worst years of the drought were still ahead, but the impacts of the dry spell on California’s energy system were already clear to Szinai. As water levels dropped, so too did hydropower generation—an energy gap that was filled by fossil fuels. “That increased costs and emissions for the state,” Szinai reflected later, “and really drove home the point that the electric sector is really closely tied to the water sector, and both were quite vulnerable to climate change impacts, like droughts, that are going to be more common.”
Szinai went looking for a comprehensive assessment of the effects of climate change on the links between water and energy, what researchers call the water–energy nexus, in the state. To her surprise, there wasn’t one. Previous research had evaluated the impacts of climate change on each sector in isolation. As a graduate student in the Energy and Resources Group at the University of California, Berkeley, Szinai is working to fill that void. In a recent study published in Environmental Research Letters, Szinai and her colleagues present a framework that outlines the links between and vulnerabilities of the state’s energy and water systems. The findings can be used to evaluate how both climate change and our adaptation decisions might affect the interconnected systems.
It’s a first and an “exhaustive” quantification of the linkages between energy and water, according to Nathalie Voisin, a water resources engineer at the Pacific Northwest National Laboratory who was not involved in the study. “It’s unique that the researchers put an emphasis on the linkages, when usually the linkages are points of limitation in other papers.”
A New Climate in California
The team used California, a region where water and energy are tightly linked, as a case study for the framework. Previous research has shown that the state is particularly vulnerable to climate change, which is expected to play out in ways that stress both water and energy supplies.
California’s water system is largely dependent on snowpack, which stores the winter rains until the summer months when the water is really needed. The state’s snowpack is expected to decrease by as much as two thirds before the end of the century, which means California will need to overhaul its water supply systems.
Meanwhile, rising temperatures will reduce the efficiency of electricity transmission lines while increasing demand for power-hungry air conditioners.
On top of these challenges, the state is leading the country in its goals to decarbonize. “It’s [at both] the forefront of climate adaptation and the forefront of climate mitigation,” said Andrew Jones, a staff scientist at Lawrence Berkeley National Laboratory and a study coauthor.
As the state works to decarbonize and adapt to a new climate, understanding how changes to water and energy supply and demand will interact is increasingly important—and exceedingly complex, especially once you factor in the decisions resource managers must make to adapt.
Imagine a drought in a semiarid, agricultural state like California: As water supplies fall, demand for irrigated water will rise; hydropower generation will fall, even as more electricity is needed to pump groundwater to the surface or to transport water from the wet northern reaches of the state to the drought-prone southern stretches. Indeed, many of the technologies to which managers turn to make up for a water shortfall, including desalination and water recycling, are energy intensive. Any decision in one sector inevitably ripples through to the other.
The challenge for Szinai and her colleagues was to determine which linkages were most relevant to resource managers, and then put some numbers to them. Just how much will temperatures rise and snowpack fall in California in the coming years, and what will those measures mean for supply and demand across the energy and water sectors? “What we try to do in this work is bring a little bit of order to the disorder,” Szinai said.
A Range of Impacts
Reviewing the available literature, the team found that the direct impacts of climate change were quite large for both sectors. By the end of the century, California could see a water supply shortage of as much as 18 billion cubic meters, or a surplus as large as 24 billion cubic meters. The huge range stems largely from uncertainties in our understanding of snowmelt. “We don’t really know if total annual precipitation will go up or down with climate change,” said Jones. “But we do know that much more of the precipitation will be as rain, rather than snow, and that the snowmelt will happen earlier, so there’s this important question about how much of that streamflow can actually be captured as water supply.”
On the energy side, the team found that the state could face a 6-terawatt-hour electricity shortage by the end of the century in the best-case climate scenario, and a 42-terawatt-hour shortage under the worst. Increased demand for air conditioning in a hotter climate had the largest impact on electricity, followed by decreased hydropower generation.
Szinai noted that researchers could be underestimating the combined effects of climate change on the two systems. The current paper looks at these impacts on an annual scale, but the effects could be compounded in the summer months, when temperatures rise and precipitation falls.
“Economic and social sciences are also critical in evaluating water and energy systems transitions,” Voisin added. “Those aspects, not captured in this study, would inform [adaptations] in the future. For example, the cost of water pumping might not be recovered by the value of the agriculture products.”
Perhaps most interesting, the team found that the impacts of adaptation decisions could be just as large as the impacts of climate change itself. In other words, in solving one problem, resource managers could create another. For example, trying to meet a water shortfall with desalination would require an additional 20–50 terawatt-hours of energy, an amount larger than the climate-induced shortages in electricity from hydropower losses, transmission efficiency decreases, and air-conditioning combined. However, meeting the shortage with water conservation strategies, targeted to urban areas, saved significant amounts of energy.
“How we adapt to climate change in the water sector can exacerbate or offset impacts on the grid,” Szinai said, “and so those interactions shouldn’t be ignored in planning.”
—Kate Wheeling (@KateWheeling), Science Writer