SIGNIFICANCE OF CONDITIONING TO PIEZOMETRIC HEAD DATA FOR PREDICTIONSOF MASS-TRANSPORT IN GROUNDWATER MODELING

Transmissivity and head data are sampled from an exhaustive synthetic reference field and used to predict the arrival positions and arrival times of a number of particles transported across the field, together with an uncertainity estimate. Different combinations of number of tra nsmissivity data and number of head data used are considered in each o ne of a series of 64 Monte-Carlo analyses. In each analysis, 250 reali zations of transmissivity fields conditioned to both transmissivity an d head data are generated using a novel geostatistically based inverse method. Pooling the solutions of the flow and transport equations in all 250 realizations allows building conditional frequency distributio ns for particle arrival positions and arrival times. By comparing thes e frequency distributions, we can assess the incremental gain that add itional head data provide. The main conclusion is that the first few h ead data dramatically improve the quality of transport predictions.