ABSTRACT
Six tracer tests, several of which were conducted simultaneously, two pre-project tracer tests, and a potentiometric map based on water wells, springs, and stream elevations, were used to delineate the Rio Springs groundwater basin, located about 24 km (15 miles) east-northeast of Mammoth Cave National Park, Kentucky. The investigation was conducted as a Groundwater-Source Protection Area (GSPA) Demonstration Project. The results of the series of tracer tests were used to iteratively revise the potentiometric map that guided the design of successive tracer tests. The rationales are given for various investigative techniques used and decisions made. The techniques are described.
The recharge area for the Rio Springs groundwater basin was rigorously estimated to be 13.4 km2 (5.18 mi2) but could range as high as 16.8 km2 (6.5 mi2). This area includes an indeterminate amount of groundwater pirated from an adjacent surface-water basin, Bacon Creek. Such inclusions is inferred because the boundary of the Rio Springs groundwater basin is beyond (and outside) the boundary of its surface water basin (the topographic divide) where this latter boundary can be drawn. The indeterminacy is a consequence of much of the basin being overlain by up to 60 m (200 feet) of dissolutionally-slumped disaggregated sand and gravel from an unconformable channel of Pennsylvanian sandstone and conglomerate.
In a sense, the Rio Springs groundwater basin was not suitable for a demonstration project because its hydrogeology is as complex as it was subsequently discovered to be. In another sense, it was highly suitable because the results acquired suggest that the methods employed are capable of deciphering the hydrogeology in almost all carbonate terranes—if they are correctly employed.
The results of the investigation may be used for response to environmental emergencies, local and regional planning, resource protection through a Groundwater-Source Protection Area Plan for Rio Springs, and public education. Many results are relevant to the study, interpretation and protection of water supplies in other karst terranes and are discussed. Conclusions, applicable to maximizing the efficiency and reliability of similar investigations elsewhere are given.
