Modelagem do aporte de sedimentos aplicada à bacia hidrográfica contribuinte da PCH Costa Rica (MS) e proposta de mitigação do assoreamento
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Data
2016-01-28
Autores
Zanella, Bruno Pavanelli [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A avaliação do potencial de produção de sedimentos de uma bacia hidrográfica contribuinte de uma hidrelétrica é de extrema importância para a análise da viabilidade de implantação de uma planta geradora, sobretudo quando se trata de uma Pequena Central Hidrelétrica (PCH), pois o assoreamento pode comprometer a longevidade do empreendimento. Este estudo teve como objetivo aplicar e avaliar modelos de predição de aporte de sedimentos na bacia hidrográfica contribuinte da PCH Costa Rica, no Estado de Mato Grosso do Sul, gerados pelos softwares SWAT e InVEST. A bacia contribuinte desta PCH, com aproximadamente 1.200km², é integrante da bacia do Alto Rio Sucuriú, e apresenta escassez de dados de séries históricas de hidrologia e sedimentologia. A modelagem pelo software SWAT e InVEST permitiu verificar que a produção de sedimentos ocorre em altas taxas na bacia contribuinte desta PCH. A perda total de solo nesta bacia obtida pelo InVEST foi de 19,23 Mg ha-1 ano-1 (2.392.353,10 Mg ano-1), superior em 2,2 vezes o valor gerado pelo software SWAT, de 8,54 Mg ha-1 ano-1 (1.062.402,15 Mg ano-1). O total de sedimentos que efetivamente chega ao canal de adução da PCH Costa Rica estimada pelo InVEST foi de 100.674,20 Mg ano-1 de sedimentos, enquanto o SWAT apresentou um total 10,43 vezes superior (1.049.521,72 Mg ano-1). A diferença obtida entre os dois modelos pode ser atribuída às peculiaridades de cada software, sendo utilizada no InVEST, a relação máxima do aporte de sedimento definida em 80% que não é aplicada no SWAT representa a capacidade máxima de retenção possível em cada célula. A modelagem da perda de solo em bacias hidrográficas realizada pelos softwares SWAT e InVEST mostrou-se promissora, com elevada correlação entre si e com o Método de Einsten Modificado. Estes sedimentos são carreados e se acumulam nos cursos d’água, gerando problemas operacionais para esta PCH, que necessita de dragagem constante para permitir o funcionamento do empreendimento, gerando custos que não foram previstos na concepção do projeto. Diante deste cenário foi proposta a recomposição vegetal das áreas degradadas por processos erosivos intensos, com a utilização de biotecnologia, em sistema de plantio direto de espécies nativas do Cerrado em consórcio com leguminosas inoculadas com rizóbio. A simulação do InVEST para o cenário futuro com recomposição vegetal de 13,78 km2 das APPs hídricas desta bacia gerou uma redução na produção de sedimentos de 6.464,99 Mg ano-1, demonstrando que a adoção de práticas conservacionistas pelos produtores da bacia contribuinte da PCH Costa Rica pode amenizar os processos erosivos, aumentar a capacidade produtiva dos solos e diminuir os custos desta hidrelétrica com o desassoreamento do canal de adução.
The evaluation of sediment production potential in a hydroelectric watershed is extremely important for the deployment of assessing the feasibility of a generating plant, especially in the case of a Small Hydroelectric Plant (SHP) because the sediment deposition may compromise the longevity of the project. This study aimed to implement and evaluate sediment delivery prediction models in the watershed of SHP Costa Rica in the state of Mato Grosso do Sul, generated by SWAT and InVEST software. The basin of this SHP, with approximately 1.200km², is an upper portion of the Sucuriú river basin and presenting scarcity of data time series of hydrology and sedimentology. Modeling by SWAT and InVEST software has shown that the production of sediments occurs at high rates in the basin of this SHP. The total soil losses in watersheds of this SHP obtained by InVEST was 19,23 Mg ha-1 ano-1 (2392353,10 Mg ano-1), higher than the value obtained by SWAT software with 8,54 Mg ha-1 ano-1 (1062402,15 Mg ano-1). The sediment that reaches the adduction channel of SHP Costa Rica estimated by InVEST is 100,674.20 Mg year-1 of sediments, while the SWAT has a total 10.43 times higher (1.049.521,72 Mg ano-1). The difference obtained between the two models can be attributed to the peculiarities of each software being used in InVEST, the maximum ratio of sediment contribution set at 80% which is not applied in SWAT is the maximum capacity possible retention in each cell. The modeling of soil loss in river basins performed by SWAT and InVEST software proved promising, with high correlation with each other and the method of Modified Einstein. These sediments are carried and accumulate in streams, creating operational problems for SHP Costa Rica, which requires dredging to allow operation, and generates costs that were not anticipated in the initial project. In this scenario was proposed a plant recovery of degraded areas with the use of biotechnology in no-tillage system of native Cerrado species intercropped with legumes inoculated with Rhizobium. The simulation of InVEST for future scenario with plant recovery of 13.78 km2 of hydric permanent preservation areas in the SHP Costa Rica basin generated a reduction of 6464.99 Mg year-1 in the total loss of sediment in small watersheds. The adoption of conservation practices by farmers of the SHP Costa Rica basin can mitigate the erosive processes, increase the productive capacity of soils and reduce the costs of this hydropower plant with dredging in the adduction channel.
The evaluation of sediment production potential in a hydroelectric watershed is extremely important for the deployment of assessing the feasibility of a generating plant, especially in the case of a Small Hydroelectric Plant (SHP) because the sediment deposition may compromise the longevity of the project. This study aimed to implement and evaluate sediment delivery prediction models in the watershed of SHP Costa Rica in the state of Mato Grosso do Sul, generated by SWAT and InVEST software. The basin of this SHP, with approximately 1.200km², is an upper portion of the Sucuriú river basin and presenting scarcity of data time series of hydrology and sedimentology. Modeling by SWAT and InVEST software has shown that the production of sediments occurs at high rates in the basin of this SHP. The total soil losses in watersheds of this SHP obtained by InVEST was 19,23 Mg ha-1 ano-1 (2392353,10 Mg ano-1), higher than the value obtained by SWAT software with 8,54 Mg ha-1 ano-1 (1062402,15 Mg ano-1). The sediment that reaches the adduction channel of SHP Costa Rica estimated by InVEST is 100,674.20 Mg year-1 of sediments, while the SWAT has a total 10.43 times higher (1.049.521,72 Mg ano-1). The difference obtained between the two models can be attributed to the peculiarities of each software being used in InVEST, the maximum ratio of sediment contribution set at 80% which is not applied in SWAT is the maximum capacity possible retention in each cell. The modeling of soil loss in river basins performed by SWAT and InVEST software proved promising, with high correlation with each other and the method of Modified Einstein. These sediments are carried and accumulate in streams, creating operational problems for SHP Costa Rica, which requires dredging to allow operation, and generates costs that were not anticipated in the initial project. In this scenario was proposed a plant recovery of degraded areas with the use of biotechnology in no-tillage system of native Cerrado species intercropped with legumes inoculated with Rhizobium. The simulation of InVEST for future scenario with plant recovery of 13.78 km2 of hydric permanent preservation areas in the SHP Costa Rica basin generated a reduction of 6464.99 Mg year-1 in the total loss of sediment in small watersheds. The adoption of conservation practices by farmers of the SHP Costa Rica basin can mitigate the erosive processes, increase the productive capacity of soils and reduce the costs of this hydropower plant with dredging in the adduction channel.
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Palavras-chave
Hidrelétricas, Produção de sedimentos, SWAT, InVEST, Hidrossedimentologia, Hydroelectric plants, Production of sediments, Hydro-sedimentology