José L. S. Pinho

Eutrophication vulnerability analysis: A case study

River Cavado water quality variability was studied for eutrophication vulnerability assessment at a new surface water supply intake. Since the river flow regime is artificially controlled by upstream multipurpose reservoirs, mathematical modelling was applied in evaluating alternative management scenarios. Due to the fact that surface water quality at intake location is mainly affected by a wastewater treatment plant effluent discharge 5 km upstream, algae and nutrients concentration simulations have been worked out in order to identify critical situations. Different algal concentration profiles along the river were obtained for local conditions of light energy, water temperature and estimated nutrient loads, showing high probability of eutrophication occurrence for some of the simulated scenarios. The discussion of results of this study appears to be very useful for river basin wide water management policies evaluation.

Comparison Between Two Hydrodynamic Models for Flooding Simulations at River Lima Basin

According to EU flood risks directive, flood hazard maps should include information on hydraulic characteristics of vulnerable locations, i.e. the inundated areas, water depths and velocities. These features can be assessed by the use of advanced hydraulic modelling tools which are presented in this paper based on a case study in the river Lima basin, Portugal. This river includes several flood-prone areas. Ponte Lima town is one of the places of higher flood risk. The upstream dams can lower the flood risks if part of its storage capacity is allocated for mitigating flood events. However, proper management of dam releases and the evaluation of downstream river flows should be considered for preventing flood damages. A hydrological and a one-dimensional hydrodynamic model were implemented, and at a particular flood-prone town, inundation was assessed using a two-dimensional model. The hydrological model is based on the well known Sacramento model. For this purpose, two different modelling implementations were analysed: a model based on a finite element mesh and a model based on rectangular grids. The computational performance of the two modelling implementations is evaluated. Historical flood events were used for model calibration serving as a basis for the establishment of different potential flood scenarios. Intense precipitation events in the river’s basin and operational dam releases are determinant for the occurrence of floods at vulnerable downstream locations. The inundation model based on the unstructured mesh reveals to be more computationally efficient if high spatial resolution is required. A new combination of software tools for floods simulation is presented including an efficient alternative for simulation of 2-D inundation using a finite element mesh instead of a grid.

Parameter estimation for eutrophication models in reservoirs

Excessive eutrophication is a major water quality issue in lakes and reservoirs worldwide. This complex biological process can lead to serious water quality problems. Although it can be adequately addressed by applying sophisticated mathematical models, the application of these tools in a reservoir management context requires significant amounts of data and large computation times. This work presents a simple primary production model and a calibration procedure that can efficiently be used in operational reservoir management frameworks. It considers four state variables: herbivorous zooplankton, algae (measured as chlorophyll-a pigment), phosphorous and nitrogen. The model was applied to a set of Portuguese reservoirs. We apply the model to 23 Portuguese reservoirs in two different calibration settings. This research work presents the results of the estimation of model parameters.

Numerical Modelling Of Oil Spills In Coastal Zones. A Case Study

A computational structure has been developed to forecast the time-space evolution of oil spills in marine environments. This structure was developed taking into account widely used mathematical formulations for oil spreading and weathering processes, A Eulerian transport model, that uses hydrodynamic results obtained with a two-dimensional and a quasi three-dimensional hydrodynamic model, was used to predict the oil slick transport and spread. This paper presents the general characteristics of the computational structure and the results of its application to a real case study: the Cereal accident in October 1994,

Web-Based Decision Support Framework for Water Resources Management at River Basin Scale

In recent years a major effort has been done to make water quality modelling tools available for water resources management at a river basin scale. The European water framework directive clear states that these tools must be used in making the diagnostic of surface water bodies water quality status and to anticipate the impact of measures to be implemented in order to achieve a good ecological status by 2015 in European waters (European Commission 2000; Rekolainen 2003; Horn et al. 2004; Ravesteijn & Kroesen 2007; Volk et al. 2008).

Coastal Defense in NW Portugal: The Improbable Victory

Coastal defense in Portugal has a long history. The first attempts to resist coastal change date from early in the twentieth century, when the town of Espinho saw its most seaward streets damaged by wave impact. A coastal defense work (a “muralha”, or wall) was built. The 1980s saw the building of several groins at different locations in Portugal. The fight against the sea continued during subsequent years in a tentative effort to achieve an “artificially stable” coastal zone. Coastal retreat and thinning of beaches continued, especially downdrift of structures. The pattern has progressively revealed the inefficiency of efforts to stabilize the coastline. The underlying causes have not been addressed and indeed are poorly understood. Coastal defense is simply a temporary and palliative means of addressing the impacts of coastal erosion and, sometimes gives a false sense of security to coastal populations. In this chapter an overview of the NW Portuguese coastal defense structures is presented, their efficiency is discussed and some representative examples are described. Some recommendations are presented to create a more efficient coastal zone management policy.

Mathematical Modelling Of Oil Spills In TheAtlantic Iberian Coastal Waters

This paper presents an information system that is being developed as a management support tool for accidental oil spills in the Atlantic coastal waters of the Iberian Peninsula. Oil slick transport is predicted using a transport model (two-dimensional eulerian model implemented in the RMA4 program) associated with hydrodynamic models (two-dimensional models implemented in the RMA2 program and three-dimensional models implemented with the POM program). These hydrodynamic models can simulate tides, winds, river discharges and density gradients for induced currents. Data used to establish the models’ bathymetry and boundary conditions are also presented. Geo-referenced data are processed via a Geographical Information System tool. Data on the N/T Prestige oil spill processed by means of this information system and preliminary simulation results are also included.

Mathematical Model for Primary Production Within the Portuguese Coastal Zone

The oceanic primary production represents 40% of the Earth’s primary production. For this reason, it is admissible to state that the oceanic primary production plays a fundamental role in the global carbon cycle.

Numerical model for hydrodynamics simulations of Trabalhador channel

Purpose The purpose of this paper is to construct a numerical model for the numerical analysis of the hydraulic transient profile in Trabalhador channel for filling and emptying maneuvers and to determine the water level in time. Model results support operational managers in the decision-making process. Design/methodology/approach Physical data were provided for the construction and calibration of the numerical model. The equations of Saint-Venant were approximated by a finite difference scheme and the numerical model was written in Fortran. The results of filling and emptying of the channel simulations were compared with the measured water levels. Findings Measured water levels and those simulated by the numerical model have shown good correlation. The time recorded for the filling and emptying of the canal was also close between the measured and simulated data. The simulation design flow pointed to inundation in the channel banks. Simulation water levels were slightly higher than those measured. Research limitations/implications In this model, the combination of canals and pressure conduits was not considered. Practical implications The findings confirm the measured time for filling and emptying of the canal, as well as inundation of canal banks for the maximum design flow. These results help in the management process. Originality/value This paper presents a numerical model for hydraulic transient analysis in channels with good agreement with the field data.

A Multi-criteria Approach for Erosion Risk Assessment Using a New Concept of Spatial Unit Analysis, Wave Model and High Resolution DEMs

In this work, field data and model outputs were integrated, processed and analyzed in a GIS environment in order to assess the vulnerability to erosion and to produce associated risk maps using a multi-criteria approach. Erosion risk assessment methodology was developed based on morphological, hydrodynamic, and meteorological indicators that were computed using data obtained from a short term monitoring program. It was applied to a stretch on the NW coastal zone of Portugal. Comparing this methodology to previously developed ones, there are three main distinctive aspects to be considered: (i) the coastal stretch was segmented for computation of indexes (susceptibility, exposure and risk), accordingly to specific coastal types (ii) a new set of vulnerability variables is proposed; and (iii) erosion impact indicators computed from detailed building and beaches data that was extracted from aerial photos.