Magic Sand Saves Water in the Desert
In the desert, the sun sucks water out of the ground. But a layer of water-repellent sand just 5–10 mm thick works like a lid: air passes through, but water is blocked. Evaporation drops by 63–83%.
Under such a lid, sand behavior flips upside down. Normally, fine sand loses moisture 37% faster than coarse sand because it heats up more.