Final answer:
A drainage basin is an open system because it receives inputs like precipitation and has outputs such as river discharge, which includes the transfer of water, sediments, and dissolved minerals.
Step-by-step explanation:
A drainage basin is considered to be an open system because it both receives input and provides output to its surroundings. Inputs to a drainage basin include precipitation, such as rain or snow, which then contributes to surface runoff or infiltrates into the ground to become groundwater. Furthermore, a drainage basin also has outputs, such as river discharge, which is the volume of water moving through a river channel over time, eventually making its way to the ocean. The process is driven by gravity and can include not only water but also sediments and dissolved minerals.
Rivers within these basins play a crucial role in providing irrigation for crops and as a source of drinking water for cities. The input-output relationship within a drainage basin is a fundamental part of the hydrological cycle and the management of water resources.