CONTAMINANT TRANSPORT IN KARST AQUIFERS

The heterogeneous, multiple-porosity karst aquifers in the Upper Mississippi Valley Paleozoic carbonates and sandstones exhibit several different patterns of contaminant transport. The patterns in plan view include convergent dendritic drainage patterns, divergent often radial flow patterns and anastomosing patterns. In cross section there are complex, semi-perching relationships that interweave saturated, unsaturated and multi-phase flow phenomena. Contaminant transport velocities range from km/day to m/day. The entire range of intermediate flow systems exist. Several of different flow systems are typically present in each volume of aquifer. Much of the storage in these aquifers occurs in the parts of the systems with slow flow velocities, which may be in laminar flow regimes much of the time. Most of the transport occurs in conduits (with a wide variety of geometries) in which the flow is typically turbulent. These complex, diverse, heterogeneous karst systems can be successfully characterized and effectively managed, but neither task is simple or cheap.