Environmental

‘Grey infrastructure’ can’t meet future water storage needs, Stanford research reveals

‘Grey infrastructure’ can’t meet future water storage needs, Stanford research reveals

A study led by Stanford University researchers provides a global overview of the role dams and reservoirs play in providing water storage, revealing so-called “grey infrastructure” won’t be enough to meet future demands for hydropower and agricultural irrigation.

As demand for food and energy grows, water will only become more precious. The analysis, published in Renewable and Sustainable Energy Reviews, underscores the necessity of exploring demand- and supply-side alternatives, such as other renewable energy sources and nature-based approaches for water storage.

“Water storage is a critical and globally limited resource,” said study lead author Rafael Schmitt, a lead scientist at the Stanford-based Natural Capital Project. “Our study shows that the solutions of the past are insufficient and can be damaging to already overstretched freshwater ecosystems.”

Dams and reservoirs fuel hydropower, store water for irrigation, provide drinking water and lower flood risks. They also disrupt fish migrations and displace people and terrestrial ecosystems, among other impacts. To help policymakers make more informed decisions about grey infrastructure and alternatives, Schmitt and co-author Lorenzo Rosa, a principal investigator at Carnegie Science and an assistant professor (by courtesy) of Earth system science in the Stanford Doerr School of Sustainability, focused on crucial gaps in the understanding of how dams and reservoirs contribute to food and energy security.

The researchers used machine learning to quantify the multipurpose roles of the world’s 6,000 largest dams and reservoirs. Analysis revealed that dammed reservoirs store about 1,000 times the volume of California’s largest man-made lake, Shasta Lake. Of that, less than 5% reaches irrigated crops. The dams analyzed provide 505 GW of hydropower, 40% of total global hydropower capacity, according to the study. Worldwide, about 3,700 dams have been identified for potential development. If all of them were constructed, they could provide about 60% more energy and about 40% more stored water for irrigation, according to the study.

Despite this potential, the analysis shows that deficits persist in some countries and regions. The projections highlight that even with the construction of several thousand new dams, there won’t be enough hydropower and stored water to meet energy and irrigation needs in India, central Europe and several Asia-Pacific nations. Those needs will be considerable: The study projects global demand for hydropower will grow about 35% between now and 2050 and the global need for stored irrigation water will grow by about 70%. As demands for irrigation and hydropower grow, gaps between sectoral needs and what dams can provide will widen. As both hydropower and irrigation often rely on the same dammed reservoirs, the risk for conflicts between these sectors increases as well.

“Our study by no means advocates for building more dams,” said Schmitt. “What we urgently need is a global debate about how to meet water storage needs for critical sectors.”

Addressing these needs sustainably will require taking pressure off grey infrastructure through policies that promote renewable energy technologies; nature-based solutions such as increasing soil water retention; and alternative water storage solutions such as small storage ponds, managed aquifer recharge, and improved agricultural water management, according to the study’s authors.

Where hydropower lags behind demand, other renewable energy sources could pick up the power slack and even allow dam operations to shift focus toward irrigation. Conversely, increasing reliance on non-grey infrastructure storage options could make it easier for dam operations to shift toward producing more energy, making it possible to build fewer and smaller hydropower projects. Where both hydropower and stored irrigation water are in short supply, the need for alternatives to dams and reservoirs will be all the more acute, according to the researchers.