California wants to cover its canals with solar panels

Despite a very wet winter, California’s water scarcity woes aren’t finished.

Gov. Gavin Newsom has resisted declaring the drought to be over. Just this week, a proposal from President Joe Biden raised the possibility of new, painful water cuts for California. And the state seems increasingly trapped in a pattern of severe storms followed by extreme drought, without much of a happy medium.

So perhaps it goes without saying that water conservation will continue to be a central issue in the Golden State for years to come.

A new state-funded project in the San Joaquin Valley hopes to find a new way to build drought resilience. The idea is simple: Cover the state’s canals and aqueducts with solar panels to both limit evaporation and generate renewable energy.

“If you drive up and down the state, you see a lot of open canals. And after year after year of drought it seemed an obvious question: How much are we losing to evaporation?” said Jordan Harris, co-founder and CEO of Solar AquaGrid, a company based in the Bay Area that’s designing and overseeing the initiative. “It’s just common sense in our eyes.”

The California Department of Water Resources is providing $20 million to test the concept in Stanislaus County and to help determine where else along the state’s 4,000 miles of canals — one of the largest water conveyance systems in the world — it would make the most sense to install solar panels. The project is a collaboration between the state, Solar AquaGrid, the Turlock Irrigation District and researchers with the University of California, Merced, who will track and analyze the findings.

“This hasn’t been tried in the U.S. before,” said Roger Bales, an engineering professor at UC Merced who specializes in water and climate research. “We want these to eventually be scaled across the western U.S., where we have a lot of irrigated agriculture and open canals.”

California’s efforts got a jump start from a 2021 study published by Bales and his colleagues, who determined that covering the state’s canals with solar panels could reduce evaporation by as much as 90% and save 63 billion gallons of water per year — enough to meet the residential water needs of more than 2 million people.

The team identified other possible upsides: The installations could generate large amounts of energy; reduce algae growth and the need for maintenance by limiting sunlight falling on the water; enhance the functioning of the solar panels by allowing them to stay cool near the water; and improve air quality by creating an energy source that would limit the need for diesel-powered irrigation pumps.

The sheer number of benefits documented in the study eased hesitations about the idea and “kind of changed our thinking,” said Josh Weimer, spokesperson for the Turlock Irrigation District, which volunteered its 250 miles of canals in Stanislaus County for the pilot. Another benefit for the district, which is also a power provider, is that it doesn’t need to buy new, costly tracts of land to install solar panels since the canals are already its property.

The project, expected to break ground this fall, will start out on just 2 miles of canals in the Central Valley district. I recently visited one of them in the small agricultural town of Ceres, just outside Modesto off Highway 99, where the concrete-banked canal winds through shady orchards and past narrow farm roads frequented by tractors.

The results will very likely be closely watched. Harris told me he had already been contacted by water districts and canal operators around the world — including in Spain, the Philippines and Brazil — that are curious about replicating the design.

“This is a global issue, and potentially a big contributor to a global solution to evaporative losses and renewable energy generation at the same time,” Harris said.