Can America’s canals double as solar farms?

Some 8,000 miles of federally owned canals snake across the United States, channeling water to replenish crops, fuel hydropower plants and supply drinking water to rural communities. In the future, these narrow waterways could serve an additional role: as hubs of solar energy generation.

A coalition of environmental groups is urging the federal government to consider carpeting its canals with solar panels. The concept was pioneered in India a decade ago and will soon be tested in California for the first time. Early research suggests that suspending solar arrays over canals can not only generate electricity in land-constrained areas but may also reduce water evaporation in drought-prone regions.

Last week, more than 125 climate advocacy groups, led by the Center for Biological Diversity, sent a letter to the U.S. Department of Interior calling on the agency to deploy solar over its 8,000 miles of canals and aqueducts. The agency’s Bureau of Reclamation owns and operates the infrastructure, often in partnership with local irrigation and water districts.

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Such a move would potentially generate over 25 gigawatts of renewable energy — enough to power nearly 20 million homes — and reduce water evaporation by tens of billions of gallons, according to the letter. To come up with the national numbers, the groups extrapolated from previous research led by the University of California, Merced that analyzed the potential benefits of covering California’s 4,000 miles of canals.

“We’re trying to elevate this as a good solution that you should be doing,” Brett Hartl, the government affairs director at the Center for Biological Diversity, said about the letter. ​“You don’t have to pave over thousands of acres of land…at the expense of lost habitat.”

The solar-canal campaign reflects a broader tension that’s building as the U.S. transitions away from fossil fuels toward cleaner energy sources.

Sprawling utility-scale solar systems are facing pushback in rural Midwestern communities and in Maine, Texas, Virginia and elsewhere. Local opponents have argued that big solar projects would take farmland out of production, reduce property values and possibly harm wildlife. The American Clean Power Association, an industry trade group, has argued that community opposition is making it harder for solar developers to build projects at the rate that’s needed to address climate change.

The Biden administration is pushing to permit 25 gigawatts of solar, wind and geothermal energy projects on public lands by 2025, the bulk of which will likely include utility-scale projects in the western United States. Solar canals could, in theory, provide a way to meet some of those goals without disturbing ecosystems or affecting communities.

“It builds on the conventional wisdom that you’d better build solar over existing infrastructure first before you take natural lands or productive farmland out of use,” said Roger Bales, an engineering professor at UC Merced who specializes in water and climate research. Existing sites can include rooftops, landfills, parking lots and former industrial lands.

For all their promise, solar canals remain more of an idea than a widely deployed reality. But efforts are underway to start installing and testing projects in water-scarce parts of the country.