Scientists there found that the rate of evaporation can be below 76 centimeters (30 inches) per year at the low end, to 305 centimeters (120 inches) per year on the high end. Evaporation happens when a liquid substance becomes a gas. When water is heated, it evaporates. The molecules move and vibrate so quickly that they escape into the atmosphere as molecules of water vapor. Evaporation is a very important part of the water cycle. Heat from the sun, or solar energy, powers the evaporation process. It soaks up moisture from soil in a garden, as well as the biggest oceans and lakes. The water level will decrease as it is exposed to the heat of the sun.