Determination of the interaction of groundwater and surface water in karst terrane is particularly difficult because of the complex hydraulic interconnections of fractures and solution openings in carbonate rocks. Brahana and Hollyday [1988] indicated that dry reaches of streams can be used as indicators of groundwater reservoirs. In their study of south-central Tennessee, they used infrared remote sensing and ground reconnaissance of stream channels to identify dry reaches of river, and they used test drilling to confirm the presence of subsurface reservoirs. They found that sheet-like dissolution openings developed parallel to bedding created the groundwater reservoir.
Several studies of lakes and rivers in the karst terrane of Florida indicate the complex interaction of the lakes with groundwater, an interaction that is complicated by groundwater pumping from the underlying carbonate Floridan aquifer. Lee and Swancar [1994], using field data from piezometer nests as well as modeling, indicated that groundwater in the surficial aquifer flowed into Lake Lucerne, Florida, from the water-table aquifer, but that lake water seeped downward in the middle of the lake to the Floridan aquifer. Furthermore, they found that the gradient increased during periods of pumping from the Floridan aquifer. A study by Patton and Klein [1989] indicated that heavy pumping from the Floridan aquifer is changing the hydrology of the Peace River basin. For example, not only have springs ceased to flow, but as the water table declined additional sink holes were created which caused groundwater flow patterns to be altered and flow in the Peace River to be affected.
Organisms have also been found to be indicators of hydrologic conditions in karst terrane. Vervier and Gibert [1991] quantified the interactions between water, solutes, and organisms at the interface between a stream and a groundwater outlet from karst terrane. The location of the ecotone showed marked spatial fluctuations according to the prevailing hydrology, interactions were strong during high flows and were negligible during low flows.