Présentations Colloques

    Session 8.04: Isotopic and residence time tracers
    Kanisa Jaroslaw Wachniew Przemyslaw
    Calibration of transient transport model for fissured-karstic aquifer in southern Poland with the aid of tritium data
    Numerical transport models used to predict migration of pollutants in groundwater systems are traditionally based on groundwater flow models calibrated against observed hydraulic heads and recharge rates. However, flow model calibrated against hydraulic heads does not guarantee that transport model will perform well and transport model needs independent calibration.**A 3D flow and transport model was build for phreatic, fissured-karstic limestone aquifer of Jurassic age located in southern Poland. The aquifer is a sole source of potable water for Czestochowa agglomeration and neighboring municipalities. The aquifer surface area of 951.5 km2 was subdivided into a grid of 100 by 100 meters. Twelve horizontal layers were distinguished in the model. The MODFLOW and MT3DMS codes were used. Groundwater flow was simulated for steady-state conditions, while transport was simulated under transient conditions. The flow model was calibrated using observed hydraulic heads. Tritium concentration was measured in total 21 sites (mostly abstraction wells). They were sampled over the period 1991-2015. The tritium data available for the studied system were used to calibrate the transport model.**Initially, the modeled tritium concentrations revealed significant disagreement with respect to the measured concentrations, while good fit between calculated and observed hydraulic heads was maintained. In the course of the calibration process the recharge rate and hydraulic conductivity were modified in some parts of the aquifer such a way that measured and modeled tritium concentrations converged for most of the investigated wells. For some wells, however, still significant discrepancies remain. This disagreement suggests that some changes in the conceptual model of the studied system are still needed.**Acknowledgements. The study was supported through the statutory funds of the AGH University of Science and Technology (projects No. and and the BONUS-185 programme (project Soils2Sea).


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