An intersting measure I've seen used in Spain to alleviate evaporation in water reservoirs is to place a few layers of hollow floating balls on top of the water

An intersting measure I've seen used in Spain to alleviate evaporation in water reservoirs is to place a few layers of hollow floating balls on top of the water. It blocks the sun from heating up the water. It rained a bit the last few days in Catalonia but the forests are very dry and the summer could be dangerous for fires if we don't get more rain.