California is about to launch an experiment to cover aqueducts with solar panels, a plan that if scaled up might save billions of gallons of otherwise evaporated water while powering millions of homes.

Project Nexus in the Turlock Irrigation District launches in mid-October amid Western North America's worst drought in 1,200 years and as human-influenced climate change exacerbates the dry spell.

The $20 million project, funded by the state, is due to break ground in two locations. One is a 500-foot (152-meter or about 0.3-mile) span along a curved portion of the canal in the town of Hickman, about 100 miles (160 km) inland from San Francisco. The other is a mile-long (1.6-km long) straightaway in nearby Ceres.

Based on a similar project in the west Indian state of Gujarat, the project is the first of its kind in the United States, said University of California Merced project scientist Brandi McKuin. The Turlock project was inspired by a research paper McKuin published in 2021.

Modern California was built thanks to 20th century infrastructure that delivers water from the wet north to the arid south, a network McKuin said now totals 4,000 miles (6,400 km) of canals.

Covering those canals with solar panels would reduce evaporation, avoid using other land for solar farms and reduce aquatic weed and algae growth, saving on maintenance costs, McKuin said.

"It's really exciting to test our hypothesis and the paper we published. We'll have an opportunity to really understand if those benefits pencil out in the real world," McKuin said.

It would also help California meet its renewable energy goal of achieving 50% clean energy generation by 2025 and 60% by 2030.

If all 4,000 miles of canals were covered with solar panels, it could produce 13 gigawatts of renewable capacity, roughly half of what California needs to meet its carbon-free energy goals, she said.

A gigawatt, or 1 billion watts, is enough to power 750,000 homes.

McKuin's research also calculated water savings of 63 billion gallons (238 million cubic meters), enough to supply 2 million people and irrigate 50,000 acres (20,000 hectares) of cropland.

Like other utilities throughout the state, Turlock Irrigation District Water & Power is required to expand its renewable energy capacity.

"If this is something that works on these first two miles of Project Nexus that we're doing, there's the potential that this could scale to multiple locations," said Josh Weimer, Turlock Water & Power's external affairs manager.