Solar over water on the Casa Blanca Canal

The Casa Blanca Canal carries irrigation water through the Gila River Indian Community near Sacaton, about 30 miles south of Phoenix. Since early October 2024 it has also carried something above the water: a canopy of solar panels on supports spanning the canal, the first operational solar-over-canal project in the United States.

The idea is old and sensible. An open canal in the Arizona sun loses water to evaporation all day, every day, and the same sun beats down on land that could hold panels. Covering a canal does both jobs in the same footprint: it shades the water and it makes electricity.

A canal, a community, a partnership

The project belongs to the Gila River Indian Community, and the partnership behind it is federal. In November 2023 the Community and the U.S. Army Corps of Engineers signed a project partnership agreement to study and build the crossing. The following month, in December 2023, the Department of the Interior announced $5.65 million in federal Inflation Reduction Act funding for it.

That funding mattered. Solar-over-canal designs are more expensive per panel than a flat desert array, because every panel needs a structure over moving water. Federal money is what lets a first-of-its-kind project prove its numbers in the real world instead of on paper.

Covering a canal does two jobs at once: it makes electricity and it shades water in a state that worries about both.

What got built

The numbers are modest on utility scale and large for what they prove. About 3,000 feet of canal is covered, carrying roughly 2,500 solar panels. The nameplate capacity is 1.31 megawatts, with roughly 2.26 million kilowatt-hours of generation expected per year, according to the Bureau of Reclamation.

The water question, answered honestly

The strongest claim made for solar over canal is water savings, and it deserves the careful version. Shading a canal does reduce evaporation. One researcher puts the benefit for this stretch of the Casa Blanca Canal on the order of 8 to 12 acre-feet a year.

Keep that number honest. It is a proof of concept, not a river-scale fix. Arizona's water math is measured in millions of acre-feet, and a single canal crossing will not move it. What the project can do is measure how panels, water, and canal maintenance coexist, on a real working canal, in real desert weather, and publish what it learns.

The wider math

Scale is where the idea gets interesting. Salt River Project maintains more than 130 miles of canals serving the Phoenix area, and every mile is open water under a fierce sun. If covering canals proves out technically, the Valley's irrigation network becomes a map of candidate sites.

The most quoted study of that potential came from UC Merced in 2021. It estimated that covering California's roughly 4,000 miles of canals could, in principle, save tens of billions of gallons of water a year and generate on the order of 13 gigawatts of power. Read the hedges in that sentence: in principle, on the order of. Nobody has covered 4,000 miles of anything. Arizona now has about 3,000 feet of it, which is how honest engineering starts.

What to watch

Three questions will tell whether the Casa Blanca crossing is a curiosity or a template. Does annual output land near the Bureau of Reclamation's estimate? Do the panels and their supports hold up through dust season and monsoon storms? And do other canal operators, SRP included, study the results closely enough to copy what works?

The last question is the one this record will keep watching. The first operational solar-over-canal project in the country sits on a working canal south of Phoenix, and it has started answering it.