Modelagem da dinâmica de algas e cianobactérias em um reservatório de abastecimento
Nenhuma Miniatura disponível
Data
2018-06-22
Autores
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal de Goiás
Resumo
Shallow reservoirs, with large surface area and long hydraulic retention
times, present conditions conducive to the development of cyanobacteria.
Due to the potential risk that cyanobacteria can cause to public health, the
importance of the management of water bodies to control the toxic blooms,
especially in reservoirs destined to the public supply, is evident. Thus, there
is a clear need to develop techniques that can help existing monitoring, with
the possibility of extending the area of coverage in monitoring programs.
Thus, the present study aimed to combine several methods of data
acquisition, mainly obtaining continuously, such as the use of sensors for in
situ evaluation of phytoplankton, especially cyanobacteria, through the
detection of chlorophyll-a and phycocyanin, as well as the use of remote
sensing for phytoplankton monitoring and with this information to build
water quality prediction scenarios through mathematical modeling. The
procedure aimed to improve data acquisition, especially the spatialization of
data. For this purpose, the dynamics and water quality of the João Leite
reservoir was characterised over 30 months using physical, chemical and
biological parameters and trophic status index, to know the seasonality of
the quality of the of the water body and present the main parameters and
factors of water quality change. A continuous and spatial phytoplankton
monitoring method was proposed for mapping concentrations of chlorophyll-
a and cyanobacteria from Sentinel-2 satellite images with in situ and
inferential observations to evaluate the performance of these to provide
information on cyanobacterial blooms. The CE-QUAL-W2 model was
calibrated from field data to evaluate the water quality dynamics and
hydrodynamics of the reservoir. As a result, João Leite reservoir presented
characteristic and similar patterns of the variation of the parameters in
hydrological periods, and the results showed that the use and the occupation
of the soil reflect in the characteristics of the quality of the water. In the
majority of the evaluated points and times, good oxygenation of the waters
and low concentrations of nutrients were demonstrated, being proved by the
trophic state indexes. Both chlorophyll-a and cyanobacteria showed
correlation between data measured in situ and estimated. The results can
considered satisfactory since with the data of reflectance it was possible to
validate the atmospheric correction, and the maps of estimate of chlorophyll-
a and cyanobacteria presented the places and the months more prone to the
greater proliferation of cyanobacteria. Thus, these results demonstrate the
importance of the use of remote sensing for the monitoring of water quality,
since with the use of this tool there is greater possibility of point coverage,
being able to have a synoptic visualisation of the studied environment,
identifying the most subject areas to the proliferation of cyanobacteria. The
results of the modeling indicate that the reservoir presents periodic
stratification, and in the warmer months the stratification is more evident
and that in the colder months a mixture of the water column is noticed,
possibly due to in those months there are more incidental winds in the
region. In general, the highest values of algae and cyanobacteria occur in
the warmer months, where there is a higher solar incidence and larger
periods of thermal stratification occur. It was also presented that the amount
of algae and cyanobacteria on the surface changes the amount of oxygen
dissolved in the surface region while the demand for sediment oxygen may
be associated with both the oxygen consumption in the sediments and can
also be used as a way to simulate the consumption of oxygen by the
submerged organic matter, which is visible in the shallower areas of the
reservoir. The results of the CE-QUAL-W2 model provided a comprehensive
understanding of the spatial and temporal dynamics of the parameters
analyzed during the modeling periods. The application of this model with the
integration of fluorometers and remote sensing for the evaluation of water
quality, should be better suited to water resource managers, to help them
better understand the dynamics of physicochemical and biological processes
and to be used as a warning system in cases of cyanobacteria blooms and to
propose the best mitigation strategies.
Descrição
Palavras-chave
Citação
SALGADO, A. A. Modelagem da dinâmica de algas e cianobactérias em um reservatório de abastecimento. 2018. 161 f. Tese (Doutorado em Ciências Ambientais) - Universidade Federal de Goiás, Goiânia, 2018.