Most rainfall ends us a runoff on the landscape.
When rain hits the ground it begins to flow overland downhill. Of course, a significant percentage of it gets absorbed into the ground, evaporated by the sun, and absorbed by plants, and then evaptranspired. After a light rain you may not notice much runoff at all. But after a heavy rainfall, or if the ground is already saturated, you might see sheets of water running downhill...always seeking a stream it can run inot, so it can continue to participate in the natural water cycle.