Which term best describes the shape of a watershed?

The term "variable" accurately captures the diverse and irregular shapes that watersheds can take on. Watersheds are defined by the area of land that drains into a particular body of water, such as a river or lake, and their contours are influenced by a myriad of factors including topography, geology, and land use. This variability means that no two watersheds are alike; they can range from steep and narrow to broad and flat, often incorporating various landforms and geographic features.

In contrast, the other shapes—rectangular, round, or square—suggest uniformity and geometric simplicity that does not reflect the complexity inherent in natural watersheds. The natural processes that shape the landscape result in intricate drainage patterns and boundary lines that are anything but uniform, aligning more closely with the term "variable."