Ponor (Nerskaya)

A ponor, also sometimes spelled ponor, is a natural opening in karst terrain through which surface water drains underground. The term "Nerskaya" in parentheses specifies that this particular ponor is located in the Nerskaya River basin, Russia. Ponors are a key feature of karst hydrogeology, facilitating the development of underground drainage systems, including caves and underground rivers. They are distinct from sinkholes, though the terms are sometimes used interchangeably. A sinkhole is typically formed by the collapse of surface material into an underground void, while a ponor is a pre-existing opening that captures surface water flow. The effectiveness of a ponor in draining water depends on factors such as the size of the opening, the permeability of the surrounding rock, and the gradient of the land. Ponors contribute significantly to the local and regional water cycle by diverting surface water to groundwater reservoirs.