A decade ago, the western Indian state of Gujarat experimented with something nobody had ever done before – putting solar panels over top of an irrigation canal. It solved the problem of finding land for solar panels, land in India being expensive and ownership often controversial, and it provided electricity for people in rural areas that utilities had found hard to serve. 

But it also turned out that those panels did a whole lot more. Less of the water evaporated in the hot climate. The water in the canals cooled the panels so they were more efficient. And there were far fewer weeds to clog up the canals. (Similar results have been found from floating solar panels placed on hydro dams.)