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Finite Element Modelling of the Hydrodynamics and Water Quality of the Patos Lagoon System, Brazil

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Objectives:

The aim of this research project is to simulate the physical processes of hydrodynamics, transport and dispersion, and water quality in the Patos Lagoon and Estuary system, Brazil, using and 2 dimensional finite element hydrodynamic and water quality model (TELEMAC-2D and WQFLOW-2D). It is intended to use the model as a predictive tool to aid the decision making process for the rehabilitation and management of degraded environments within the estuary. This study hopes to provide advancement in the knowledge of simulating a complex system for the purposes of practical management. Specific objectives are :

Summary of Research:

The Patos Lagoon and estuary system is of major importance to the communities of the Rio Grande do Sul State, with the consequence of being subject to the influence of multiple and conflicting human impacts, many of which have the potential for pollution. Such activities include recreation and tourism; abstraction of drinking water and the disposal of domestic waste water; the industries of fertiliser production, fish processing, and petroleum refining; artisanal fisheries and aquaculture; agriculture; and navigation. Within the boundaries of the estuary are several shallow embayments, which are degraded environments suffering from the effects of pollution from many of these sources.

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Figure 1. Image of the Patos Lagoon taken by a Multi-angle Imaging SpectroRadiometer aboard the "Terra" Satellite on 27th December, 2001 (NASA/GSFC/LaRC/JPL, MISR Team); a. South America; b. Southern part of Patos Lagoon Estuary showing Saco da Mangueira. Black markers show the locations of water level recorders during 1999

A two dimensional depth averaged finite element hydrodynamic model, TELEMAC-2D, has been calibrated to investigate the hydrodynamics of the Patos Lagoon system, and the results are currently being used to drive the water quality module WQFLOW-2D for the simulation of nutrients, primary production and bacteria with particular geographical focus on the Saco da Mangueira.

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Figure 2. Space Discretisation for Model (3734 nodes and 6717 triangles): a. Entire Domain; b. Estuary; c. Saco da Mangueira and Access Channel

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Figure 3. Modelled and Observed Longitudinal Velocity at Praticagem 2nd to 20th August 1999 Wind Coefficient 1.61x10-6

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Figure 5. Modelled Velocity and Elevation (29/7/99 12:00) with Observed Elevation and Wind at Praticagem

 

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