What does the hydrologic cycle describe?

The hydrologic cycle describes the continuous movement of water in various forms between the Earth's surface and the atmosphere. This cycle includes processes such as evaporation, condensation, precipitation, infiltration, and runoff. Essentially, it illustrates how water transitions from liquid to gas and back to liquid form, facilitating the distribution of water across the globe, influencing ecosystems, weather patterns, and climates.

While the other options discuss important aspects of water, they do not encompass the broader and essential concept of the hydrologic cycle. For instance, sediment transport in rivers pertains specifically to a component of river dynamics rather than the overall movement of water. The stages of water purification processes focus on the treatment and cleaning of water, which is a singular aspect of water management rather than its natural cycle. Lastly, the interaction between human activities and water resources highlights the impact of human actions on water availability and quality but does not speak to the fundamental, natural processes that govern how water moves through the environment.