Modelling of helium transport in groundwater along a section in the Pannonian basin

Underground water flow in sedimentary basins controls the distribution of d issolved salts and gases, and their concentrations may therefore be used as indicators of the flow direction. Recent measurements of the He-4 concentr ation in deep waters of the Pannonian basin have great importance in this r espect. This paper presents an example of the simultaneous computation of w ater flow and helium distribution along a section crossing the Great Hungar ian Plain. The model consists of three permeable layers. The boundaries of the layers are prescribed using geologic sections constrained by ample bore hole and seismic data. The results of the finite-difference calculations ar e fitted to the observed helium concentrations using a least-squares algori thm that varies the model parameters;The significance of the model is that it reconstructs the structure and flux of the groundwater flow and estimate s the poorly known hydrogeological parameters of the flow regime such as hy draulic conductivities, conductivity anisotropy and dispersion coefficients . The statistical uncertainty of the estimated parameters is around half an order of magnitude. An estimate of the regional average of the incoming he lium flux is also obtained. The total helium flux in the Great Hungarian Pl ain at the surface is within the range observed in old stable continental a reas of the Earth. (C) 1999 Elsevier Science B.V. All rights reserved.