A river basin is the land water must cross to reach a river. A river basin collects all available water from various tributaries, creeks and streams in its area.
A river basin collects all water from an area, then moves it through the water system, where it eventually empties into an ocean or sea. A river basin is generally composed of many areas called watersheds. A watershed is similar to a river basin, although the area of land and the amount of water collected is smaller. A river basin can contain several watersheds that collect water from streams, lakes and rivers of varying sizes.