Video narration
Rivers usually begin as tiny trickles of moving water on higher ground. One common source is rainfall: water hits the land, runs downhill as runoff, and gathers in small channels. Another source is melting snow or ice; as temperatures rise, meltwater drains into gullies and streams. Rivers can also start from groundwater. Rain and snow soak into the soil, and some of that water slowly moves underground until it seeps out as a spring, feeding a small stream even when it hasn’t rained. As these little flows travel downhill, they meet and merge—one stream joins another, then another—creating a wider, stronger current. Over time, that growing flow carves a clearer path, becoming a river that keeps moving from high places to low places, on its way to a lake, a larger river, or the ocean.