Placing solar arrays over canals would prevent water loss and improve panels’ energy harvest.

Covering canals with solar panels helps the panels to operate more efficiently — and the shade helps to keep the canals’ water from being lost to evaporation.

Most solar-panel arrays are located on the ground or on rooftops. But some researchers have explored options, such as putting floating panels on reservoirs, that aim to reduce water loss.

Brandi McKuin at the University of California, Merced, Elliott Campbell at the University of California, Santa Cruz, and their colleagues analysed the economic and financial effects of placing solar panels over California’s 6,350 kilometres of canals. These channels transport water from mountains and reservoirs to farm fields and communities downstream.

Covering the canals with solar panels would prevent evaporation of roughly 40,000 cubic metres of water — 16 Olympic swimming pools’ worth — from each kilometre of canal every year. The panels would also perform better than on land, because of the cooler microclimate over the water.

The benefits outweigh the costs of having to build the panels over the canals, the team concludes.