Hydrodynamic Modeling of the Mundaú-Manguaba Estuarine-Lagoon System, Brazil

University essay from Lunds universitet/Avdelningen för Teknisk vattenresurslära

Abstract: Background Lagoons are shallow coastal water bodies which occupy 13 % of the world’s total coastlines. Healthy lagoons have a rich aquatic fauna and can provide an economic benefit for the people living in its vicinity. Due to anthropogenic activities, the water quality in many lagoons is deteriorating. The Mundaú-Manguaba Estuarine-Lagoon System is no exception. BOD-rich water from the nearby sugar plantations along with large amount of untreated sewage from the nearby city of Maceió are contributing to the deteriorating water quality in the lagoon system. A computerized model can be a useful tool in terms of forecasting the effects of different actions taken to improve the water quality. Such a model already exists, called IPH-ECO, but uses data collected in 1984 and consequently needs a thorough overhaul. The morphology of the lagoon system has changed mainly due to sediment infilling; therefore the model needs to be updated regarding bathymetry and sediments. Objectives The purpose of this master thesis is to construct an updated hydrodynamic model over the Mundaú-Manguaba Estuarine-Lagoon System in Brazil. In order to achieve this, bathymetry and sediment information needs to be collected, analyzed and finally digitized. A field camping will be executed where data regarding depth and salinity variation in the lagoons will be collected. Two scenarios will be tested with the newly calibrated model to demonstrate the usability of the model. Procedure This thesis was initiated in September 2013 with a literature review where lagoons in general and the Mundaú-Manguaba Estuarine-Lagoon System in particular were studied. Data collection and field measurements were carried out in Maceió, Brazil, between January and March 2014. During this time a new field campaign was carried out in order to get updated data concerning depth and salinity. To run the IPH-ECO model the boundary conditions had to be updated. That includes tidal fluctuations, river flows, bathymetry and Chezy coefficients. With the data collected from the sensors various new simulations were performed in IPH-ECO in order to calibrate the model. When the calibration process was completed the correlation between model and sensor was evaluated. Lastly the scenarios were simulated. Conclusions Mundaú lagoon could be calibrated well hydrodynamically with high correlation between sensor data and model. The calibration of Manguaba lagoon did not provide as satisfying results due to the lack of data concerning bathymetry and sediments. The two different scenarios were simulated successfully and show that the model can be used to predict future flooding in case of an extreme wet season and improve the water quality by the decreased renewal time which a new ocean inlet would bring. It is recommended that a new bathymetry survey is conducted in the southern part of Manguaba so that the whole lagoon system can be calibrated hydrodynamically. It is also recommended that calibration continues regarding lagoon salinity.

  AT THIS PAGE YOU CAN DOWNLOAD THE WHOLE ESSAY. (follow the link to the next page)