I imagine a trillion of these floating along the coast of the western United States, little landing pads (and solar powered charging stations) for a trillion drones that can move the freshly desalinated water from the ocean to the nearest forest fire. You need a drone cloud 500 million strong to deliver 100 million gallons of fresh water to X location immediately? No problem. Need a drone cloud to water your 20,000 acre vineyard? Coming right up. Who needs clouds?
Water is very heavy though. For watering crops I think you would do better in terms of energy efficiency with land-based infrastructure. At the very least, if you're going with drones, you ideally want something more energy-efficient than quadcopters.
