what is a drainage basin

A drainage basin, also known as a catchment area, catchment basin, river basin, or watershed, is an area of land where all the surface water flows into a single point, such as a river mouth, or into another body of water, such as a lake or ocean. The drainage basin includes both the streams and rivers that convey the water as well as the land surface from which water drains into those channels. The boundaries of a drainage basin are determined by watershed delineation, which is a common task in environmental engineering and science. The process of finding a drainage boundary is referred to as watershed delineation, and finding the area and extent of a drainage basin is an important step in many areas of science and engineering. Drainage basins are important in ecology because as water flows over the ground and along rivers, it can pick up nutrients, sediment, and pollutants, which can affect the ecological processes along the way as well as in the receiving water source.