From the linked article:

The idea is simple: install solar panels over canals in sunny, water-scarce regions where they reduce evaporation and make electricity.

A study by the University of California, Merced gives a boost to the idea, estimating that 63 billion gallons of water could be saved by covering California’s 6,437 kilometres of canals with solar panels that could also generate 13 gigawatts of power. That’s enough for the entire city of Los Angeles from January until early October.