The upper Floridan aquifer ranks among the most productive aquifers in the world. The Floridan is a carbonate aquifer characterized by the presence of sinkholes and large, fully-saturated cave systems. These caves tend to dominate groundwater flow patterns over a range of scales; from meters to kilometers. Continuum-based numerical approaches to solving groundwater flow or contaminant transport problems in this setting have proven difficult and often inadequate for practical purposes.

As an alternative, we present here a mathematical, geological, and numerical basis for a novel approach to flow in conduit-dominated karst aquifers. The new model combines both probabilistic and discrete features: a hybrid model. The probabilistic component relates the ability of a conduit to carry flow to the geometric relationship between the spring and the strike of the conduit. The discrete component of the model relates recharge via precipitation to diffuse flow through the Floridan aquifer. The probabilistic and discrete components are coupled, in a fashion similar to dual-porosity models, such that the aquifer surrounding a conduit provides groundwater from storage during low flow conditions. Preliminary results of the model applied to a spring basin in Florida will also be presented.