[1] In this paper, we study the influence of high log-conductivity variance ð 2 Y Þ and localscale dispersion on the first two concentration moments as well as on higher-order moments, skewness, and kurtosis, in a 2-D heterogeneous aquifer. Three different heterogeneity structures are considered, defined with one and the same global isotropic Gaussian variogram. The three structures differ in terms of spatial connectivity patterns at extreme log-conductivity values. Our numerical approach to simulate contaminant transport through heterogeneous porous media is based on the Lagrangian framework with a reverse tracking formulation. Advection and local-scale dispersion are two competing and controlling mechanisms, with a relative ratio defined by the Peclet number (Pe); hydraulic log-conductivity variance 2 Y in the simulations is assumed to be one or eight. The term local-scale dispersion is used as a combined effect of molecular diffusion and mechanical dispersion. Uncertainty of the concentration field is quantified by the second-order moment, or the coefficient of variation (CV C ) as a function of the sampling position along a centerline, Peclet number, and 2 Y , as well as by higher-order moments, i.e., skewness and kurtosis. The parameter 2 Y shows a strong influence on the concentration statistics, while the three different structures have a minor impact in the case of low heterogeneity. The results also indicate that for 2 Y ¼ 8, the influence of local-scale dispersion is significant after five integral scales (I Y ) from the source for the connected (CN) field, while in case of a disconnected field, the local-scale dispersion effect is observed after 20I Y from the source. In the case of unit 2 Y , local-scale dispersion acts very slowly affecting concentration uncertainty at distances higher than 20I Y from the source. Our inspection of Monte Carlo concentration skewness and kurtosis with the ones obtained from the Beta distribution show the discrepancies for high 2 Y and CN log-conductivity structure.Citation: Srzic, V., V. Cvetkovic, R. Andricevic, and H. Gotovac (2013), Impact of aquifer heterogeneity structure and local-scale dispersion on solute concentration uncertainty, Water Resour.

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Sea water intrusion (SWI) has been widely recognized as a global problem, significantly influencing coastal aquifers, mostly through reduced water quality and agricultural production indicators. In this paper, we present the outcomes of the implementation of two independent real-time monitoring systems, planned and installed to get insights on groundwater dynamics within the adjacent coastal aquifer systems, one located in the Neretva Valley, southeastern Croatia, the other located south of the Venice lagoon, northeastern Italy. Both systems are presented with technical details and the capacity to observe, store, and transmit (Neretva site) observed values in real-time. Analysis of time series reveals the significant influence of the sea level oscillations onto the observed groundwater electrical conductivity (EC) and piezometric head values, while precipitation rate is detected as a driving mechanism for groundwater parameters in shallow geological units. The installed monitoring systems are shown to be of great importance to provide qualitative and quantitative information on the processes influencing groundwater and surface water dynamics within two coastal systems.