At Badwater Basin, big rainstorms sometimes flood the bottom of the valley. They cover the salt pan with a thin sheet of standing water. This makes new lakes, but the lakes do not last long. This is because the average of rain that falls every year is much lower than the a 150-inch annual evaporation rate, so all the water evaporates away. This means that even a 12-foot-deep, 30-mile-long lake would dry up in a single year. While the basin is flooded, some of the salt dissolves and goes back into the basin as clean crystals when the water evaporates.