Abstract Analyses of 441 water samples from 15 sample sites, mainly springs and sinking creeks in the southcentral Kentucky karst, were used to determine hardness, P CO 2 , and state of saturation with respect to calcite and dolomite. Most of the waters are undersaturated with respect to calcite and more undersaturated with respect to dolomite, in agreement with recent kinetic models. Time series data revealed chemical fluctuations on both weekly and seasonal time scales. Much of the short-term variation and some of the seasonal variation in the hardness and saturation index parameters can be accounted for by dilution effects from storm and seasonal runoff. Seasonal cycles in CO 2 partial pressure arise from a dependence of soil CO 2 on temperature and the growing season. Waters from different locations in the aquifer system are chemically distinct and fit into the concept of a hydrochemical facies.