How do sinking streams become part of an underground drainage system?

In karst landscapes, sinking streams become part of an underground drainage system when surface water flowing from areas underlain by insoluble rock reaches the border of a karst region and disappears into the subsurface.1

This process integrates surface water into the underground network through the following mechanisms:

• Conduit Formation: As water flows into closed depressions or sinkholes, it percolates along horizontal and vertical cracks in soluble bedrock, such as limestone. Through chemical weathering, these cracks are widened and deepened over time, eventually forming continuous conduits that serve as integrated drains for the rapid movement of water.213
• Tributary Development: These sinking streams act as inlets that feed into the underground system, effectively becoming tributaries of the subterranean drainage network.1
• System Integration: Depending on the catchment area, these streams may inject large quantities of water at a single point, contributing to the development of specific cave passage patterns, such as single-conduit systems or branchworks where multiple inlets join to form master streams.4

Ultimately, these underground conduits function as the primary drainage routes for the region, often emerging at the surface as large springs.13