Perth Laboratory – Public Seminar Series 2009

Geochemical characterisation of saturated groundwater of the Middle Eocene Brussels aquifer in the Dijle Basin, Belgium

Mr Luk Peeters
Department of Earth and Environmental Sciences
Katholieke Universteit Leuven, Belgium

Thursday 8 October 2009 at 3.30pm, CSIRO Auditorium

Abstract
The Middle Eocene Brussels aquifer is an unconfined aquifer in a heterogeneous, locally calcified, sand aquifer covering a large part of Central Belgium. The aquifer is heavily solicited for industrial, agricultural and drinking water production. In this study the observed major ion chemistry is explained in terms of geochemical processes as well as in terms of land-use, groundwater flow and calculated residence time. In the first part of the research a water table map of the unconfined aquifer is interpolated using the Bayesian Data Fusion framework. This interpolation methodology combines traditional, ordinary kriging with the results of a simplified groundwater model.

In a second phase an exploratory data analysis is carried out on the major ion chemistry to identify groupings in the data and relationships between variables, using Self-Organizing Maps (SOM). Self-Organizing Maps are a neural network technique to visualize multidimensional data and perform nonlinear exploratory data analysis. The results are used to formulate a preliminary geochemical conceptual model of the aquifer.

This preliminary conceptual model doesn’t incorporate any information on groundwater flow and transport. Therefore a groundwater model of the aquifer is developed to asses the infiltration area, flow lines and residence time for each sampling location. The generalized likelihood uncertainty estimation (GLUE) methodology is used to asses the variation in infiltration area and residence time due to uncertainty in hydraulic conductivity and spatially distributed recharge. The Self-Organizing Map analysis of major ion chemistry is extended with the results of the groundwater model, namely the characteristics of the infiltration area (land-use, soil type, recharge, ...) and calculated residence time in saturated and unsaturated zone. The preliminary geochemical conceptual model is updated based on these results. The final geochemical conceptual model is used as basis for geochemical mass balance modeling to quantify the contribution of each process in the observed chemical composition.

About the speaker
Mr Peeters obtained his master degree in Geology from Katholieke Universteit Leuven, Magan Cum Laude, Belgium in 2003. He is currently doing his PhD at the same institute. His PhD research is on qualifying and quantifying the processes affecting the groundwater chemistry in the Central Belgium. In addition to his PhD he has been teaching and conducting research since 2004 at the same institution. His main areas of expertise are in groundwater modelling, geochemical modelling, geostatistics, and exploratory data analysis.

Mr Peeters has accepted a Groundwater Modeller position in CSIRO Land and Water. He is expected to join the Groundwater Hydrology Group of the Hydrology Program in Adelaide during early 2010 after completing his PhD.

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