Overflow conduit systems in Kentucky: A consequence of limited underflow capacity

The distinction between underflow and overflow elements within a karst groundwater basin is essential for the accurate mapping and analysis of groundwater basins. This paper suggests definitions for multi-flow systems and the mechanisms which cause these networks. At least four types of multi-flow features may be found in Kentucky: 1) intermittent overflow systems, 2) basin-boundary bifurcations, 3) perennial distributaries, and 4) leaky perched basins. Two major causes or mechanisms that lead to multiflow features are: 1) conduit constriction and 2) partial piracy. Regardless of the activating mechanism, ancestral conduits often provide the network through which overflow waters are transported. Intermittent overflow systems have been identified in many large karst groundwater basins as well as smaller basins such as Meriwether Spring, a water supply source in Todd County, Kentucky. Newly obtained and published tracer data, together with low-flow spring gaging and unit-discharge analysis are used to evaluate karst groundwater basins. A reassesment of perennial distributaries mapped in the Mammoth Cave region, suggests that springs within the Bear Wallow basin are connected only during overflow conditions. A distinctive ''flat-line'' recorded in the hydrograph of a water well near Hiseville in northern Barren County, Kentucky, apparently results from a high-capacity subsurface overflow system recharged by sinking creeks. Blue Spring Creek, located just east of Hiseville, maintains a lengthy surface overflow route which is capable of strongly influencing overflow routes within the subsurface.