California has begun implementing a project to cover its irrigation canals with solar panels, aiming to conserve water and generate renewable energy. The initiative, known as Project Nexus, is a collaboration between the California Department of Water Resources, Turlock Irrigation District (TID), Solar AquaGrid, and researchers from the University of California campuses at Merced and Santa Cruz.
The concept involves installing solar canopies over as much of California’s 4,000 miles of irrigation canals as possible. According to Brandi McKuin, the lead University of California researcher on the project, many people have considered this idea for decades. Roger Bales, a hydrologist and professor at UC Merced who helped launch the project, noted that he has heard similar suggestions since the 1970s.
Project Nexus is now operational and collecting data. It is based on research conducted by UC Merced and UC Santa Cruz. The pilot phase is being tested on stretches of canal managed by TID in Stanislaus County.
A decade ago, Jordan Harris, a former music executive interested in social change initiatives such as Rock the Vote and electric vehicles advocacy, began exploring the feasibility of solar over-canals with Robin Raj, founder of Citizen Group. They established Solar AquaGrid and commissioned an analysis from UC Merced in 2015.
“I think we’re all highly aware of the state of emergency we’re in, with year after year of water and energy insecurity,” Harris said. “At the same time, we need to combat climate change to produce more renewable energy and decarbonize our economy. We need bold solutions today.”
UC Merced was selected due to its systemwide initiatives in solar energy and water research. Bales assembled a team for a scientific analysis on scaling solar installations over canals across California.
The research found that covering all 4,000 miles of open canals could save up to 63 billion gallons of water each year—enough for two million people—and generate about 13 gigawatts of renewable power. This amount represents roughly one-sixth of California’s current installed capacity and about half the additional capacity needed for its 2030 decarbonization goals.
Despite initial setbacks when investors hesitated to fund further development, Harris and Raj continued their efforts alongside Bales and McKuin. Their findings were published in Nature Sustainability in 2021.
“We can’t take ownership of having the idea for solar canals,” McKuin said. “What we can take ownership of is doing a robust study of the potential for California.”
At that time, only India had implemented similar projects; however, differences in engineering challenges prompted further study specific to California’s needs.
“Had we just tried to circulate the report that we’d finished two years earlier, it would not have gotten the impact it did,” Bales said. “Being in Nature Sustainability showed that it was a peer-reviewed paper and a credible scientific result.”
Interest from state agencies led Governor Gavin Newsom’s office and others to allocate $20 million for Project Nexus’ pilot phase. TID offered sections of its canal network for testing due to its dual role as both water supplier and electricity provider.
“In 2021, we were right in the midst of a second year of a very bad drought,” said Josh Weimer, TID’s director of external affairs. “The paper was very timely… Up until this paper there had never been an analysis of the co-benefits.”
The district identified other advantages such as reduced algae growth—which could lower maintenance costs—and direct support for local electrical grids using generated power.
“When you add together all these co-benefits, then pretty soon you have something with a potential payoff quite a bit greater than the cost,” Bales stated. “When we think about 21st-century infrastructure, we need to create multi-benefit infrastructure rather than just siloing water over here [and] electricity over here.”
McKuin explained her initial skepticism: “When I first started working on this I was skeptical it could pencil out… But when we did pencil in all these co-benefits…we found that it could be cost-competitive with a ground-mounted conventional system.”
Raj emphasized innovation: “It’s no coincidence that California is unique in so many ways in terms of innovation and sustainability…the public reaction…is so strong because we live in a critical time where we need to take action quickly.”
Harris added: “We have an aging infrastructure ready to be reimagined…if we apply a dual-use mindset.” Raj concluded: “We’ve been on a journey with UC Merced since the beginning…We wouldn’t be anywhere without the University of California team.”
Plans are underway through The California Solar Canal Initiative (CSCI) involving faculty from multiple University of California campuses—including UC Merced—to expand such projects statewide via multicampus collaboration.
