Sustained flow in small Appalachian watersheds underlain by carbonate rocks

The groundwater release from storage as it relates to sustained flows in surface streams was investigated for 57 carbonate basins within the Appalachian Highlands. Comparisons were made between sustained flow and the aerial extent of limestone and dolomite rock outcrop within the basins and with the degree of karst development as measured by internal drainage through dolines and sinking streams. Data analyses by direct correlation, by factor analysis and cluster analysis showed that the basins investigated fell into two distinct populations, those with sustained flows comparable to flows observed in non-carbonate basins and those with exceptionally low sustained flows. Basins with a high degree of karst development tended to have low sustained flow because of poor groundwater storage and short residence times in carbonate aquifers with conduit-type permeability. Higher sustained flows were associated with aquifers of the diffuse-flow type.