Hydrogeological characteristics of thermal water storing Plio-Pleistocene Basin sediments in Hungary

Abstract

In Hungary 1323 thermal-water wells were drilled until 2003. (The Hungarian standard term “thermal-water well” refers, that the surface water-temperature of the well is at least 30 oC degrees.) About 85% (1123) of these thermal wells were screened for young sediments of the Pannonian basin. 90,4 percent of the actually working 851 thermal water wells (769) are yielding the examined Pliocene and Pleistocene aged layers The Fig. 1 shows the Carpathian basin areas covered by Pliocene (Pannonian s.l.) formations, together with the earliest wells of this kind.

Each thermal water occurrence of these young basin sediments are artificial ones. The geographical terms in the Carpathian basin, such as “hévíz”, “tapolca”, “toplica” etc. are usually deceptive, i. e. inside the basins only cold and luke-warm springs occurred on the surface. But on the boundaries of the mountains, hot karstic springs flows through these overlying young sediments. The first shallow thermal wells of Hungary were screened on Pannonian sandstones and conglomerates next to these thermal karstic springs. (Harkány: 1866, Félix spa: 1888 and Hévíz: 1908). The deeper, karstic origin of these springs was not known for a long time. The lake Hévíz was verified to be a karstic spring only in 1943!