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Rivers represent an essential pathway for waterborne transport, and therefore estuaries are critical coastal areas for a pollution hazard that might lead to eutrophication and general water quality deterioration. When addressing these problems, the decision makers and coastal managers often need additional skills and specialists, so they engage consultants in developing models and providing potential solutions. Different stakeholders’ interests present a challenge in the implementation process of proposed solutions. Nevertheless, if the relevant institutions were presented with a screening tool, enabling them with a certain level of solution ownership, potentially more involvement would occur. There are numerous intertwined physical processes present in the estuary ecosystem, including river discharge, tidal forces, wind-induced stress and water density variations. This research utilizes an analytical model based on ensemble averaging and near-field approximation of the advective-diffusion equation for the case of continuous, steady, conservative solute transport in a stratified, river-dominated estuary. Such an approach significantly reduces the costs and time needed to obtain enough measured data required for common statistical analysis or the need for a more complex numerical model. The developed methodology is implemented into a simple software named CPoRT (Coastal Pollution Risk Tool) within a recently conducted research project funded by European Social Fund.

Abstract:River estuaries represent one of the most valuable and nevertheless most fragile ecosystems. By their own definition they act as an interactive border between river and sea, hence obtaining characteristics of both environments and yet unique ones such as brackish water or funnel shape. On the other hand, human impact is great at such coastal ecosystem due to multiple interests involved, ranging from agricultural via transportation to recreational activities. The river generated pollution is one of the most important threats to estuary ecosystem; hence this research investigates the potential of integrated concentration statistics as a measure of dilution and risk assessment. Previous work conducted includes the definition of pollution concentration moments and corresponding probability density functions. Hence, based on developed simple analytical solution for obtaining the moments, a more robust measure of dilution is introduced -expected mass fraction. The concept of expected mass fraction was previously used by several authors concerning the dilution processes in environmental flows. Being applied for an estuarine system for the first time, such measure is defined by spatial integration of point statistics over available volume. The result is an estimate of pollutant mass existing at some downstream distance which has the concentration above defined limit value. That kind of information gives potentially useful loading estimate when doing pollution risk assessment of the estuary ecosystem.

Groundwater age is an important water property used as an indicator of groundwater quality. There have been no sufficient data and measurements underground, and that problem has been mitigated by using direct simulation of groundwater age. This paper has been motivated by the work of Daniel J. Goode, defining a rather different approach. A numerical model has been developed, using the Lagrangian approach and random walk particle tracking method, where groundwater age is calculated as a summed-up travelling time of certain particles. Basic input of this method is flow calculation; hence, in order to get the groundwater age simulation, an upgrade has been done to the existing software. Synthetic examples have been simulated for homogeneous, layered, as well as for low and medium heterogeneous aquifer systems. A stochastic analysis of heterogeneous aquifers has been done using a Monte Carlo simulation method. The results are given as groundwater age fields. Application of such an approach lays in possible estimation of the expected groundwater age at a certain location of water intake. Therefore, the calculated probability assumptions may be used as a decision support tool in cases of groundwater pollution, estimation of the level of aquifer's auto-purification, or in events where applying certain level of water treatment prior to usage is needed.