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 the result of collaboration between the California Department of Water Resources, Turlock Irrigation District (TID), Solar AquaGrid, and researchers from UC Merced and UC Santa Cruz.
Brandi McKuin, the lead University of California researcher on the project, said that many people have considered covering canals with solar panels in the past. Roger Bales, a hydrologist and professor at UC Merced who helped launch the project, noted he has heard similar ideas since the 1970s.
The concept involves installing solar canopies over California’s roughly 4,000 miles of irrigation canals. This approach could help preserve land for other uses, reduce water lost to evaporation from canals, and produce clean electricity.
After years of study and planning, Project Nexus is now operational. Scientists are collecting data from its pilot installations. “I think we’re all highly aware of the state of emergency we’re in, with year after year of water and energy insecurity,” said Jordan Harris, former music executive and co-founder of Solar AquaGrid. “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 chosen for initial research due to its involvement in systemwide initiatives such as UC Solar and UC Water. Bales assembled a team for scientific analysis on large-scale solar canal deployment in California. Their findings suggested that covering all 4,000 miles of open canals could save up to 63 billion gallons of water annually—enough for two million people—and generate about 13 gigawatts of renewable power.
Despite early setbacks when an initial investor withdrew support, Harris and Robin Raj continued work on the project alongside McKuin and Bales. The research was published in Nature Sustainability in 2021 and drew attention from state officials and utilities.
“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.”
India had previously implemented similar projects but faced challenges due to heavier materials used over rural regions with limited maintenance needs. The California team focused on adapting designs suitable for their state’s extensive canal network.
“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.”
Following these results, California allocated $20 million for a pilot program using TID’s canal infrastructure as a test site. TID provides both water for agriculture in Stanislaus County and electricity to customers—a combination that made them ideal partners.
“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.” Maintenance savings from reduced algae growth were among several additional benefits identified by TID after reviewing UC Merced’s research.
“When you add together all these co-benefits… pretty soon you have something with a potential payoff quite a bit greater than the cost,” Bales added.
Project Nexus is testing different spans—30 feet over one section and 130 feet over another—to evaluate feasibility across varying canal sizes.
The pilot will continue collecting data through completion expected in 2026 while international interest grows around replicating this model elsewhere.
“When I first started working on this, I was skeptical it could pencil out,” McKuin said. “But when we did pencil in all these co-benefits… then we found that it could be cost-competitive with a ground-mounted conventional system.”
Robin Raj reflected on innovation: “It’s no coincidence that California is unique in so many ways in terms of innovation and sustainability… And I think the reaction… is so strong because we live in a critical time where we need to take action quickly.”
Harris emphasized public openness: “We have an aging infrastructure ready to be reimagined… if we apply a dual-use mindset to generate energy on site to efficiently move water across the state.”
“We’re in this exciting position to unlock innovation because we let the science guide us,” Raj said. “We’ve been on a journey with UC Merced since the beginning and it’s been a journey of discovery. We wouldn’t be anywhere without the University of California team.”
Plans are underway through The California Solar Canal Initiative (CSCI), which includes faculty from several University of California campuses such as UC Merced, UC Berkeley, UC Irvine and UC Law San Francisco; more information can be found at New multicampus consortium looks to expand solar-over-canal projects statewide.
