Billowy and filled with life-sustaining water vapor, the cloud passes overhead without emitting a drop of rain. In times of severe drought, that cloud is a frustrating, lumbering tease. That cloud is tantalizing. Delicious even.
What that cloud needs is a kick start, a catalyst to squeeze the water out of it. It’s not science fiction; it’s called cloud-seeding. And in beyond-parched California, it may become a viable option to combat long-term water shortages.
Cloud-seeders can’t make rain appear out of clear blue sky. Rather, they create snow (and sometimes rain) where it’s most likely to occur—in clouds. Yes, that cloud is full of water vapor, but sometimes, water needs to be coaxed into forming the ice crystals needed for snow (you can see this happening in this video). The seeding devices, which are mainly on the ground, burn silver iodide into a fine mist that gets tossed up into the air. Silver iodide is an inert chemical (meaning, it won’t react chemically with much in the environment), but its structural shape is perfect for seeding ice crystals. Water vapor will collect around the silver iodide and freeze into crystals, then those crystals will precipitate as snow. The snow fills mountainsides, an, come spring, the snow melts and increases the fresh water supply.