AN EVALUATION OF METHODS FOR THE DELINEATION OF SOURCE WATER PROTECTION AREAS IN KARST TERRAINS

Various methods have been proposed for the delineation of source water protection areas (SWPA) for municipal groundwater sources including simplified variable shapes, arbitrary fixed radius, time-of-travel, hydrologic mapping, numerical modeling, and analytical methods. The selection of a delineation method is commonly based on economics with little thought given to aquifer characteristics. Many of the methods assume that the aquifer being evaluated is an equivalent porous medium. However, it is imperative to have the correct conceptual model of groundwater flow for the area of interest. Soluble rocks such as limestone, dolostone, and gypsum form positive feedback loops for dissolution processes and are therefore self organizing. These aquifers are noted for having large recharge areas, provide little if any filtration, have very high groundwater velocities (> 1 kilometer per day), contain convergent flow paths and turbulent flow, and provide a limited capacity for assimilation of contaminants. Soluble rocks compose a significant portion of the United States east of Tulsa, Oklahoma including large portions of Texas, Kentucky, Tennessee, Florida, Missouri, and Pennsylvania. The US EPA has recognized karst aquifers as one of the most vulnerable aquifer types.

We will present methods to identify self organizing (karst) aquifers and discuss the application and misapplication of various delineation methods and tools including well hydrodynamics and tracer testing.