[1] In this paper, we study the influence of high log-conductivity variance and local-scale 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 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 , as well as by higher-order moments, i.e., skewness and kurtosis. The parameter 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 , 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 , 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 and CN log-conductivity structure.

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.

Hydrogeological data availability is often limited to local areas where usual in situ tests or methods are applied (slug/bail or pumping tests, Electrical Resistivity Tomography (ERT)). Because most problems (e.g., saltwater intrusion mitigation) require problem analysis on larger scales (catchment or sub catchment), hydrogeological identification of global character is preferable. This work leads to the determination of aquifer hydrogeological parameters on the basis of observed sea level, groundwater piezometric head found inland, and barometric pressure. When applied to observed signals, the approach led efficiently to final hydrogeological characterization. After identification of dominant tidal constituents from observed signals, barometric efficiency was successfully determined. Following available information on geological settings, an appropriate conceptual model was applied and updated to count for polychromatic signals. Final determination of hydrogeological parameters relied on root mean square error (RMSE) minimization and led to determination of (i) presence of three stratigraphic units: unconfined sandy aquifer on the top, a confining layer made of clay, and a confined gravel layer; (ii) existence of the clay layer under the sea with a total length of 1400 m; (iii) a clay layer has been identified as confining one by both spectral analysis and determined leakance value; and (iv) estimated confined aquifer specific storage ranging from 2.87 × 10⁻⁶ to 4.98 × 10⁻⁶ (m⁻¹), whereas hydraulic conductivity ranged from 7.0 × 10⁻⁴ to 7.5 × 10⁻³ (m s⁻¹). Both range intervals corresponded to previous in situ findings conducted within the area of interest.

In this paper, we present an approach based on the simultaneous use of multilevel monitoring systems for the ground and surface water and wavelet-based analysis of the time series observed to detect the main mechanisms influencing the water level, electrical conductivity (EC) and temperature (T) in ground and surface water of the river Neretva coastal aquifer system. Although the area of interest is under significant impact of seawater intrusion, the presented approach enabled the insight to transient response of the system to external loadings like precipitation and irrigation system primarily. The capacity of the monitoring system has been demonstrated on two different subareas, respectively, Diga and Jasenska. While the Diga area is shown to be under significant influence of the seawater, the Jasenska area shows sensitivity to precipitation and pumping station (PS) Modric operative regime. Groundwater parameters as observed during dry periods at Jasenska show the presence of stratification. Wavelet-based analysis enabled the determination of the interdependence of the variables of interest as well as their temporal dependence. Determined regimes of the surface water, as found within the Jasenska channel, are additionally supported by the in situ profiling results, thus strengthening the findings of the study. Our findings reflect the capacity of the approach to capture for the stratification of the groundwater parameters induced by seawater intrusion and external loadings.

Our work presents a reliable procedure to obtain real-time assessment of the sea water elevation at the Kaštela Bay site to ensure the a priori warning in the case of expected coastal flooding along the site area. In its origin, the presented procedure relies on relevant data sets which are site-specific and locally observed. Observed data sets are used within the procedure to assess sea water surface elevation when induced by barometric pressure changes and wind-generated waves. Tidal-induced changes are introduced into the assessment procedure by a pre-learned algorithm which relies on long-term sea level oscillations from the relevant tidal gauge. Wind-generated wave heights are determined in the near shore area, following the features of the depth and reflection of the shoreline subsections. By coupling three mechanisms, this paper offers a unique real-time procedure to determine the sea water elevation and assess the possibility for coastline structure to be flooded by the sea. Given information is visualized in a form of mobile application that implements the algorithm and allows end users to set the notifications based on the given ruleset.

[1] In this paper, we use numerical simulations based on a Lagrangian framework to study contaminant transport through highly heterogeneous porous media due to advection and local diffusion (under local diffusion, we assume coupled effect of mechanical dispersion and molecular diffusion). The analysis of the concentration field is done for the case of a two-dimensional hydraulic conductivity domain representing the aquifer, with three log-conductivity structures that differ in spatial correlation. In addition to different conductivity structures, we focus our investigation on mild and highly heterogeneous porous media characterized by the values of hydraulic log-conductivity variance being equal to 1 and 8. In the concentration moment analysis, we show that a linear relationship exists between higher-order to second-order normalized concentration moments on a log-log scale up to the fourth-order moment. This leads to the important finding that moments of a higher than the second order can be derived based on information about the first two concentration moments only. Such a property has been observed previously for boundary-layer water channels, wind tunnels, and turbulent diffusion in open terrain and laboratory experiments. Normalized moments are shown to collapse for different types of hydraulic conductivity structures, Peclet (Pe) numbers and values. In the case of local diffusion absence, a linear log-log relationship is derived analytically and is set as a lower limit. The deviation from the lower limit is explained to be predominantly caused by the local diffusion, which needs time to evolve. In the case of local diffusion presence, we define the moment deriving function (MDF) to describe the linear log-log relationship between higher-order concentration moments to the second-order normalized one. Finally, the comparison between numerical results and those obtained from the Columbus Air Force Base Macrodispersion Experiment (MADE 1) is used to demonstrate the robustness of the moment collapse.