Javier F. Bárcena

Flushing time as a descriptor for heavily modified water bodies classification and management: application to the Huelva Harbour.

Since the flushing time is a physical descriptor used to distinguish between different types of heavily modified water bodies (HMWB), the establishment of a methodology for its calculation becomes important. In order to achieve this task, a methodological procedure involving the tide mean value and variable river flow values is proposed. The hydrodynamics were assessed using a two-dimensional model which integrates the depth-averaged mass and momentum equations in the time and space domains and includes a wet-dry point treatment method. The hydrodynamic model calibration and validation were performed on the basis of tidal gauge and velocity current measurements. A reasonable agreement with the field measurements of water elevation and velocity were achieved. On the other hand, a two-dimensional mathematical model, which solves the depth-averaged advection-diffusion equation, was properly calibrated and used to evaluate the behaviour of a conservative tracer within a water body. The transport model calibration was developed according to the field survey data carried out during late spring when the rivers flows are low. This study allowed the flushing time estimation under four scenarios showing that only the estuarine mouth presents a high renewal rate because the current velocities are higher. For heavy rain periods, a flushing time decrease was observed as river flows modify the circulation in the main channel. Neglecting the river forcing was found to be valid for the dry period.

Transport time scales as physical descriptors to characterize heavily modified water bodies near ports in coastal zones

Physical descriptors that characterize Heavily Modified Water Bodies (HMWB) based on the presence of ports should assess the degree of water exchange. The main goal of this study is to determine the optimal procedure for estimating Transport Time Scales (TTS) as physical descriptors in order to characterize and manage HMWB near ports in coastal zones. Flushing Time (FT) and Residence Time (RT), using different approaches-analytical and exponential function methods-and different hydrodynamic scenarios, were computed using numerical models. El Musel (Port of Gijon) was selected to test different transport time scales (FT and RT), methods (analytical and exponential function methods) and hydrodynamic conditions (wind and tidal forcings). FT, estimated by the exponential function method while taking into account a real tidal wave and a mean annual regime of wind as hydrodynamic forcing, was determined to be the optimal physical descriptor to characterize HMWB.

Selecting model scenarios of real hydrodynamic forcings on mesotidal and macrotidal estuaries influenced by river discharges using K-means clustering

The long-term (>30?years) simulation of 3D estuarine hydrodynamics with high-resolution meshgrids is still a challenge in numerical modeling because of the large data set of results and the computational cost requirements. Meso and macrotidal estuaries are governed by tidal action and could be influenced by river. The complexity of their behavior, suggest data mining methods may be particularly effective in selecting short-term series from a long-term series to identify the major modes of forcing variability. This study uses K-means clustering for two aims: explaining the variability of astronomical tides and river flows, and selecting scenarios of real forcings to obtain the mean behavior with a dimensional reduction. The application to the Suances estuary has highlighted the ability to classify long-term series in small number of groups. Before conducting any simulation, the proposal also determines the minimum and optimal number of groups to consider the combined effect of both forcings. KMA has the ability to classify long-term series in small number of groups.KMA clustering approach reduces effectively the forcing dimension of the system.The method explains the variability of astronomical tides and river flows.The method selects scenarios of real forcings for modelling the mean behavior.The method helps to reduce the computational cost of estuarine numerical modelling.

A method to assess the evolution and recovery of heavy metal pollution in estuarine sediments: Past history, present situation and future perspectives

A methodology to assess the historical evolution and recovery of heavy metal pollution in estuarine sediments was developed and is presented here. This approach quantifies the distribution of heavy metals in sediment cores, and investigates the influence of anthropogenic activities and/or core locations on the heavy metal pollution, by proposing and using sediment quality indices and polynomial regressions. The method has been applied to the Suances Estuary confirming its suitability as a comprehensive and practical management tool. In this estuary, the evolution of heavy metal pollution (since 1997-1998 to 2015) pointed out the deeper the sediments, the more polluted, indicating a recovery at the upper layers due to the closure and ending of washing discharges from mining, and the reduction of metal loads from industrial wastewaters. In terms of global pollution, the intertidal and subtidal sediments will require 43.1±2.8 and 8.6±0.6years to be unpolluted, respectively.