You know the water cycle from grade school: water evaporates from the oceans and rivers, condenses into clouds, falls to the ground as precipitation, and runs off into the oceans and rivers to start the process again. Except—it's a bit more complicated than that. Not all of the water makes it all the way around the cycle. As much as 40 percent of the water that falls from clouds re-evaporates before it ever touches down, and of the rain that does reach Earth, a lot never hits the ground in the first place. Watch the video below to learn more about this.