Alterações limnológicas: físico-químicas e comunidades zooplanctônicas, decorrentes da construção de pequenas centrais hidrelétricas: um estudo de caso no rio Sapucaí-Mirim (SP)
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Data
2020-01-30
Autores
Pessotto, Marco Aurélio [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Atualmente, a instalação de pequenas centrais hidrelétricas (PCHs) tem sido uma alternativa energética que se encontra em plena expansão, podendo apresentar vantagens em termos ambientais, sociais e econômicos, quando comparada à construção de grandes usinas hidrelétricas. Segundo dados obtidos na Agência Nacional de Energia Elétrica – ANEEL (sigel.aneel.gov.br), no Brasil existem 427 PCHs em operação, além de 1756 projetos previstos para implantação nos próximos anos. Contudo, apesar deste notável crescimento no número de instalações de PCHs, ainda são escassos os trabalhos que analisam as alterações limnológicas causadas por essas usinas de pequeno porte no Brasil, de forma individual ou através de efeitos cumulativos de um conjunto de empreendimentos numa determinada bacia hidrográfica. Esse estudo tem o objetivo de analisar as condições limnológicas e distribuição dos dois principais grupos zooplanctônicos cladócera e copepoda em uma cascata de três PCHs, localizadas no rio Sapucaí-Mirim/SP, bacia do rio Grande. Foram realizadas seis amostragens distribuídas entre os períodos secos e chuvosos dos anos de 2014 e 2015, abrangendo as regiões de montante, transição e região lacustre de cada reservatório. In situ foram medidas transparência da água, profundidade, perfis verticais da temperatura da água, pH, potencial de oxi-redução, condutividade elétrica, turbidez, oxigênio dissolvido e total de sólidos dissolvidos e concomitante amostras de água para análise de clorofila a, nitrogênio e fósforo totais bem como as amostras de zooplâncton realizadas do fundo à superfície com auxílio de uma rede de arrosto de 68 µm de malha de abertura. Nas regiões de montante devido à pequena profundidade (~1,5 m) a amostras foram realizadas com auxílio de um balde graduado. Para as variáveis limnológicas transparência; turbidez; temperatura oxigênio dissolvido e fósforo total ficou evidenciado o efeito de compartimentalização através dos resultados da two-way ANOVA. Já para os organismos a riqueza das espécies não apresentou diferença significativa entre a estações seca o chuvosas, no entanto para abundância ficou evidente um maior número de organismos durante o período seco com relação a destruição intra reservatório através da análise Permanova houve diferença entre as regiões de montante e zona lacustre e com relação a análise a inter reservatório o primeiro da cascata se mostrou diferente dos dois demais. Portanto os resultados demostraram, mesmo que de forma não tão contundente efeito de compartimentalização no rio após a construção de pequenas centrais hidrelétricas.
Currently, the installation of small hydroelectric plants (PCHs) has been an energy alternative that is in full expansion, and may present advantages in environmental, social and economic terms, when compared to the construction of large hydroelectric plants. According to data obtained from the National Electric Energy Agency – ANEEL (sigel.aneel.gov.br), in Brazil there are 427 SHPs in operation, in addition to 1756 projects planned for implementation in the coming years. However, despite this remarkable growth in the number of SHP installations, there are few works that analyze the limnological alterations caused by these small plants in Brazil, individually or through the cumulative effects of a set of projects in a given hydrographic basin . This study aims to analyze the limnological conditions and distribution of the two main zooplanktonic groups cladocera and copepod in a cascade of three SHPs, located in the Sapucaí-Mirim/SP river, Rio Grande basin. Six samples were taken, distributed between the dry and rainy periods of 2014 and 2015, covering the upstream, transition and lacustrine regions of each reservoir. In situ were measured water transparency, depth, vertical profiles of water temperature, pH, oxi-reduction potential, electrical conductivity, turbidity, dissolved oxygen and total dissolved solids and concomitant water samples for analysis of chlorophyll a, nitrogen and total phosphorus as well as zooplankton samples taken from bottom to surface with the aid of a 68 µm mesh aperture mesh. In the upstream regions, due to the small depth (~1.5 m) the samples were taken with the aid of a graduated bucket. For limnological variables, transparency; turbidity; temperature dissolved oxygen and total phosphorus evidenced the compartmentalization effect through the results of the two-way ANOVA. As for the organisms, species richness did not present significant difference between the dry and rainy seasons, however for abundance it was evident a greater number of organisms during the dry period in relation to intra-reservoir destruction through the Permanova analysis there was a difference between the regions of upstream and lacustrine zone and with respect to the inter-reservoir analysis, the first in the cascade was different from the other two. Therefore, the results showed, even if not so forcefully, the effect of compartmentalization in the river after the construction of small hydroelectric plants.
Currently, the installation of small hydroelectric plants (PCHs) has been an energy alternative that is in full expansion, and may present advantages in environmental, social and economic terms, when compared to the construction of large hydroelectric plants. According to data obtained from the National Electric Energy Agency – ANEEL (sigel.aneel.gov.br), in Brazil there are 427 SHPs in operation, in addition to 1756 projects planned for implementation in the coming years. However, despite this remarkable growth in the number of SHP installations, there are few works that analyze the limnological alterations caused by these small plants in Brazil, individually or through the cumulative effects of a set of projects in a given hydrographic basin . This study aims to analyze the limnological conditions and distribution of the two main zooplanktonic groups cladocera and copepod in a cascade of three SHPs, located in the Sapucaí-Mirim/SP river, Rio Grande basin. Six samples were taken, distributed between the dry and rainy periods of 2014 and 2015, covering the upstream, transition and lacustrine regions of each reservoir. In situ were measured water transparency, depth, vertical profiles of water temperature, pH, oxi-reduction potential, electrical conductivity, turbidity, dissolved oxygen and total dissolved solids and concomitant water samples for analysis of chlorophyll a, nitrogen and total phosphorus as well as zooplankton samples taken from bottom to surface with the aid of a 68 µm mesh aperture mesh. In the upstream regions, due to the small depth (~1.5 m) the samples were taken with the aid of a graduated bucket. For limnological variables, transparency; turbidity; temperature dissolved oxygen and total phosphorus evidenced the compartmentalization effect through the results of the two-way ANOVA. As for the organisms, species richness did not present significant difference between the dry and rainy seasons, however for abundance it was evident a greater number of organisms during the dry period in relation to intra-reservoir destruction through the Permanova analysis there was a difference between the regions of upstream and lacustrine zone and with respect to the inter-reservoir analysis, the first in the cascade was different from the other two. Therefore, the results showed, even if not so forcefully, the effect of compartmentalization in the river after the construction of small hydroelectric plants.
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Palavras-chave
Compartimentalização, Zooplâncton, Rio Grande, Sazonalidade, Compartmentalization, Rain season, Dry season, Cladocerans, Copepods