California Tests Solar Canals to Save Water and Power Farms

California's maze of canals keeps farms and homes alive in an increasingly dry state, but scientists just figured out how to make them work twice as hard.

Project Nexus is testing a surprisingly simple idea: put solar panels over the water. The pilot program in the Central Valley is proving that covering canals with solar could generate massive amounts of clean energy while saving water from evaporating under the hot sun.

The concept started with a 2021 study from UC Merced that made heads turn. Researchers calculated that covering all 4,000 miles of California's major canals with solar panels could generate 13 gigawatts of power (half the new solar needed to hit the state's 2030 goals) and save 63 billion gallons of water each year. That's enough water for 2 million people.

California loved the idea so much they handed over $20 million and asked: Can you prove it works?

Dr. Brandi McKuin and her team partnered with the 139-year-old Turlock Irrigation District to build test installations on two canals near Modesto. The structures now cover about one and a half football fields and generate 1.6 megawatts of power for 240,000 local residents.

The results are exceeding expectations. Shade from the panels cut water evaporation by up to 70 percent. As a bonus, blocking sunlight reduced aquatic weeds and algae by up to 85 percent, which means less maintenance and cleaner water flowing to farms.

The cooling effect of water below might even make the panels more efficient than traditional ground installations. A similar project in Arizona generated 25 percent more power than estimated, and water temperature dropped a full degree under the shade.

The Bright Side

This approach solves multiple problems with one elegant solution. California needs to get 60 percent of its electricity from renewables by 2030 while also conserving 30 percent of its open land. Solar canals don't compete with farmland or require clearing natural habitat.

Building over canals costs more than sticking panels in empty desert, but the math could work when you add up the value of saved water, lower land costs, and reduced weed removal. Josh Weimer from Turlock Irrigation District says a new report coming soon will determine if they'll expand the program.

Dr. McKuin admits covering all 4,000 miles isn't realistic, but even doing a portion could make a meaningful difference. The various shapes and conditions of California's canals mean each installation needs custom engineering.

Other places are watching closely. India built canal solar projects over a decade ago, and Arizona's Gila River Indian Community completed one in 2024. The irrigation project director there predicted a "paradigm shift" if Western states adopt the technology widely.

The timing couldn't be better for California and other dry states facing twin crises of water scarcity and energy transition.