What defines a river basin?

A river basin is defined by the area where all precipitation and runoff flow into a common water body, such as a river, lake, or reservoir. This definition captures the fundamental hydrological concept of drainage and watershed management. Within this area, the topography and land use can significantly influence how water moves towards the river, making understanding river basins crucial for water resource management, environmental conservation, and flood control.

In contrast, other options present concepts that do not holistically represent what a river basin is. A region isolated from other bodies of water suggests a separation rather than a connectivity focus typical of river basins. A stormwater management zone pertains to specific strategies for managing runoff in urban settings, while an urban area designated for water preservation emphasizes human-driven conservation efforts rather than the natural hydrological characteristics defining a basin. Thus, identifying the common drainage pattern underscores the importance of river basins in environmental management and planning.