NICHOLAS CRAWFORD AND THE KARST HYDROGEOLOGY OF THE LAGOA SANTA AREA, SOUTHEASTERN BRAZIL

In the late 1980’s karst hydrogeology was a completely new research area in Brazil, a country in which karst landscapes occupy only about 2.8% of the total area, although around 4.3 million people lives or depends on karst aquifers. The first MSc thesis on karst hydrogeology in Brazil was finished by Augusto Auler in 1994, under the supervision of Dr. Nick Crawford at Western Kentucky University. In this work, dye tracing techniques coupled with hydrochemical analyses were applied systematically for the first time in South America, allowing delineation of karst drainage basins and determination of groundwater flow routes.

The research focused in the Lagoa Santa Karst area, the best studied and most populated karst area in Brazil, affected by environmental problems related to groundwater pollution, limestone quarrying, uncontrolled urbanization and land use degradation. Very low hydraulic gradients in the area and the characteristic existence of lakes resulted in frequent dilution and long travel time for some of the fluorescein and optical brightener dye injections. Several positive connections were achieved in the two main drainage basins, Palmeiras and Samambaia Creek. An estimated 88% of the total autogenic karst water drains towards the major base level Velhas River, the remaining 12% draining towards the tributary Mata Creek. All springs are characterized by hardness dilution during the wet season, although relative variation of some of the physical parameters tend to be more subdued in some springs, such as Moinho Velho and Jaguara, suggesting a diffuse flow component.

This pioneer work served as a basis for management plans related to conservation units in the area and zoning of the increasingly urbanized Lagoa Santa Karst. The karst hydrogeology tools learned at Western Kentucky University under Dr. Crawford’s supervision were crucial in establishing a baseline for studies and management of karst aquifers in Brazil.