Which of the following describes surface water?

Surface water refers to any water that collects on the surface of the ground. This includes rivers, lakes, streams, and reservoirs, where water is visible and not hidden beneath the Earth's surface. The term emphasizes the aspect of water flowing and pooling above ground, making option B the accurate description.

The other choices refer to different types of water resources: underground water is typically referred to as groundwater; water stored in reservoirs is managed for various uses but doesn’t encompass all surface water; and water part of the groundwater supply indicates an entirely different category, focusing on aquifers and subsurface water, rather than what is directly observable on the surface. Thus, option B distinctly defines surface water by highlighting its flowing nature across the landscape.