FROM PARADIGM TO PARADIGM OR FROM TÓTH TO TÓTH IN HUNGARY'S HYDROGEOLOGY

Evolution of a conceptual pattern of groundwater flow beneath the Great Hungarian Plain (GHP) happened in four stages. Three can be related to Tóth's 1962-63 papers and work in Hungary since 1994.

The first stage is represented by Szebényi, 1955, Urbancsek, 1963, and Rónai, 1963. These studies were limited to a depth of 400 m, recognized the correlation of down- and up-ward flow with high and low topography, but did not produce a model for the observed pattern.

The second stage issued from Erdélyi (1972) who wrote to Tóth in 1971: "I feel that based on a huge amount of field data, I have succeeded to verify and further develop your flow-system concept for a large basin." He used a logarithmic vertical scale on his sections to enhance the details of flow-pattern geometry at shallow depths while avoiding the questions of distribution and origin of deep overpressures.

The third stage is due to Tóth and Almási's (2001) study of over 16 000 fluid-potential data from between a few to over 3000 m depth. Its conclusion was: the groundwater flow pattern comprises an overpressured regime of deep flow rising from the basement and driven by tectonic compression and a topography-driven meteoric regime above.

The fourth stage was produced by studies in the Duna-Tisza Interfluve (DTI) to refine the previous one and verify hypotheses based on it concerning the origin of salts in soils and lakes, and controls on the distribution of ecologically different areas (Mádl-Szőnyi and Tóth, in preparation). Tóth and Almási (2001)'s conclusions were confirmed: gravity-flow systems are perched on ubiquitously ascending waters; vertical flow occurs through conductive faults and between rock grains; vertical flows in the two regimes are opposite beneath highlands and upwards in depressions; salts originate in the basement and are distributed by groundwater discharge controlled by the interplay between the gravitational and overpressured systems. We call the current paradigm of GHP flow-pattern "The Duna-Tisza Interfluve type section".