Repositório Colecção: CEC_HID_CLI
https://hdl.handle.net/1822/1135
CEC_HID_CLI2024-03-29T09:25:47ZHydrodynamic modelling for Mondego estuary water quality management
https://hdl.handle.net/1822/7726
Título: Hydrodynamic modelling for Mondego estuary water quality management
Autor: Duarte, António A. L. Sampaio; Pinho, José L. S.; Pardal, Miguel A. C.; Neto, João M.; Vieira, J. M. Pereira; Santos, Fernando S.
Resumo: The south arm of Mondego estuary, located in the central western Atlantic coast of Portugal, is almost silted up in the upstream area. So, tides, wind and the tributary river Pranto discharges mostly drive the water circulation in this system. Annual fresh water inflow, regulated by precipitation and by sluice management practices, has a significant impact on flow velocity, salinity, N:P ratios and light extinction coefficients, which interaction controls biomass growth and loss processes. Eutrophication has been taking place in this ecosystem during last twelve years, where macroalgae reach a luxuriant development covering a significant area of the intertidal muddy flat.
A sampling program was carried out from June 1993 to January 1997. Available data on River Pranto flow discharges, salinity profiles, precipitation and nutrients loading into the south arm were used in order to get a better understanding of the ongoing changes.
Since hydrodynamics strongly affects the occurrence of macroalgal blooms, residence time can be a key parameter to characterise this influence. Integral formulations are typically based on assumptions of steady state and well-mixed systems and thus cannot take into account the space and time variability of estuarine residence times, due to river discharge flow, tidal coefficients, discharge(s) location and time of release during the tidal cycle.
This work presents the hydrodynamic modelling (1D and 2D-H) of this system in order to estimate some kinetic variables and the residence times variability to assess the main factors that control opportunistic macroalgal blooms, contributing to better environmental management strategies selection.
<b>Tipo</b>: bookPart2008-03-17T22:03:43ZComparision of numerical techniques solving longitudinal dispersion problems in the river Mondego
https://hdl.handle.net/1822/7722
Título: Comparision of numerical techniques solving longitudinal dispersion problems in the river Mondego
Autor: Duarte, António A. L. Sampaio; Pinho, José L. S.; Vieira, J. M. Pereira; Boaventura, Rui A. Rocha
Resumo: Judicious selection of mathematical models for application in a specific river basin management can mitigate prediction uncertainty. Therefore, intervention times will be established with better reliability and alarm systems could efficiently protect the aquatic ecosystems and the public health. The main purpose of this paper is to evaluate the performance of different numerical techniques when applied to river water systems dispersion modelling. A case study was developed to assess the environmental impact of Urgeiriça mining waters in a Mondego river reach, between Caldas da Felgueira and Aguieira reservoir. A monitoring program was carried out using tracer injection (rhodamine WT) to determine the in situ dispersion river water behaviour. The present work describes the methodology used in the tracer experiments, presents the concentration-time curves obtained and the performance of finite difference method (FDM) and finite element method (FEM) in a simplified river system, and compares the results of different numerical techniques application for longitudinal dispersion coefficient estimation in this river reach. The application of DUFLOW package, that includes hydrodynamics and water quality models, showed the best agreement with experimental data, allowing a reasonable support for impact assessment of different discharges scenarios in the river water quality.
<b>Tipo</b>: bookPart2008-03-17T20:57:15ZMesh generation and refinement in 2D modelling. A case study
https://hdl.handle.net/1822/7719
Título: Mesh generation and refinement in 2D modelling. A case study
Autor: Pinho, José L. S.; Duarte, António A. L. Sampaio; Vieira, J. M. Pereira
Resumo: Ria de Arosa is a bay located in the western region of Galicia-Spain, and is a well-known producer of commercially valuable shellfish, especially by raft culture of the edible mussel. Due to the ever increasing of sediments concentration in the water column, mussel productivity has been lowered in the past years. A research project on information systems for water quality assessment in that coastal zone is being developed at the University of Minho for decision making support.
Two numerical solvers of the shallow water equations based on the finite element method (FEM) were used for hydrodynamic simulations. This paper describes the general framework to generate meshes for simulations and presents the principal characteristics of a mesh generator that produces exact Delaunay triangulations, constrained Delaunay triangulations, and quality conforming Delaunay triangulations. A method for conditioned mesh refinement is also presented, where several area constraint criteria related to water depth, velocity gradients, and pollutant concentration gradients can be established.
<b>Tipo</b>: bookPart2008-03-17T18:07:46ZContribution to the preservation of healthy coastal ecosystems
https://hdl.handle.net/1822/6782
Título: Contribution to the preservation of healthy coastal ecosystems
Autor: Carmo, José S. A.; Pinho, José L. S.; Vieira, J. M. Pereira
Resumo: The release of pollutants into coastal zones from municipal and/or industrial
drainage systems is a problem with a considerable environmental impact. In
order to minimize the contamination of coastal waters in certain places (e.g.,
along beaches and in aquacultures), solutions based on the construction of
submarine sewer outfalls have been proposed. In order to ascertain the optimal
conditions for the release of an emissary, in particular the place of release, it is
necessary to characterize the hydrodynamic transport processes that govern the
evolution and mixture of pollutants in the area of interest. Circulation in the
coastal zone is complicated, given that it is determined by a set of forcing
mechanisms of diverse origins (meteorological, astronomical, large-scale ocean
circulation, etc.) that endow it with a considerable space-time variation.
Wastewater plume behaviour and characteristics depend both on the receiving
water conditions and on the discharge characteristics. Accordingly, the
implementation of a submarine outfall system requires a prior study of the site
where the outfall is to be constructed, in order to achieve optimal rates of dilution
of the pollutants released to the environment. Mathematical modelling appears to
be a very useful tool for coastal zone environmental management either for
continuous monitoring analysis or in accidental ecosystem rupture. This work
presents some results and conclusions of two case studies. The first is a
study of the pollutant cloud released at the São Jacinto submarine sewer
outfall, located about 3 km offshore and 3 km north of an important
coastal lagoon (NW Portugal). The main focus of this study was to
establish the hydrodynamic conditions in which the pollutant release
might affect the coastline (principally the existing beaches and lagoon).
The second case presents some hydrodynamic results and water quality
aspects of the Ria de Arosa (NW Spain), and also includes an assessment
of the environmental impact of wastewater discharges from nine
submarine outfalls considered in the sanitation plan of this bay. Results of
faecal matter concentration distribution were used in the discussion on the
outfall discharges’ impact on the natural water system for different
hydrodynamic scenarios. In both cases, 3D numerical models were used.
<b>Tipo</b>: conferencePaper2007-07-25T16:12:58Z