Uso da Terra e Qualidade da Água na Sub-bacia Hidrográfica do Rio Marombas

Abstract

A condução de atividades agrícolas de forma convencional, e a sua expansão no espaço e tempo podem ocasionar impactos ambientais, quer seja pela supressão de vegetação nativa e matas ciliares ou ainda pelo aumento do uso de agrotóxicos, fertilizantes e consequentes processos de lixiviação e percolação no solo que representam potenciais riscos de contaminação dos corpos d’água, de forma ainda mais expressiva quando as alterações mencionadas seguem desacompanhadas de programas de monitoramento da qualidade das águas. A Gestão Integrada de Recursos Hídricos promove a superação da abordagem setorial e fragmentada e está prevista como uma das diretrizes do Plano Nacional de Recursos Hídricos. Para que tenha êxito, um plano de gestão deve contemplar o monitoramento contínuo, possibilitando a avaliação dos RHs adjacentes às alterações de uso e de cobertura da terra das Bacias Hidrográficas. Na mesorregião Serrana do estado de Santa Catarina encontra-se a Sub-bacia hidrográfica do rio Marombas, componente da BH do Rio Canoas, fornecendo água para abastecimento industrial, irrigação para cultivos agrícolas, produção agropecuária e abastecimento público para dez municípios: Lebon Régis, São Cristóvão do Sul, Santa Cecília, Ponte Alta do Norte, Monte Carlo, Curitibanos, Frei Rogério, Brunópolis, Fraiburgo e Campos Novos. O objetivo principal deste trabalho consistiu em avaliar a influência da cobertura e uso da terra sobre a qualidade da água superficial na sub-bacia hidrográfica do Rio Marombas, utilizando a classificação da cobertura e uso da terra da área de estudo a partir de sensoriamento remoto, da determinação do Índice de Qualidade de Água para os cursos de água e da avaliação das relações entre o uso da terra e a qualidade da água por intermédio de técnicas estatísticas de Análise de Componentes Principais e Regressão Logística Multinomial. A classificação foi conduzida por intermédio de um algoritmo de Floresta Aleatória ou Random Forest, consistindo em um classificador composto por múltiplas árvores de decisão. O IQA consiste no produtório ponderado de nove parâmetros associados a qualidade da água: coliformes termotolerantes, pH, Oxigênio Dissolvido (OD), Demanda Bioquímica de Oxigênio (DBO), Nitratos, Fosfato Total, Temperatura, Turbidez e Resíduo Total após evaporação. Os resultados quanto a Classificação de Cobertura e Uso da Terra indicaram que a ocupação majoritária da sub-bacia hidrográfica do Rio Marombas é voltada às atividades produtivas ligadas à agricultura, pecuária e silvicultura, alcançando mais de 60% da cobertura total da terra. Os Índices de Qualidade de Água determinados variaram entre “Bom” e “Ruim”, valor máximo de 78,86 e valor mínimo de 45,49, demonstrando expressiva sensibilidade dos corpos d’água aos potenciais poluidores presentes na sub-bacia, apresentando valores alterados de coliformes termotolerantes, turbidez e fósforo total, reduzindo os valores dos IQAs em todas as áreas estudadas ao longo das campanhas de coleta realizadas no Rio Pessegueirinho, no Rio Marombas, Rio das Pedras e Rio Correntes. Durante o período de realização das análises, foram detectadas relações significativas entre áreas com maior ocupação das classes de cobertura/uso da terra “Agricultura”, “Pastagem”, “Mosaico de Agricultura e Pastagem” e “Silvicultura” para com os parâmetros de qualidade da água pH e turbidez.

Conducting agricultural activities in a conventional way, and its expansion in space and time (change in land use and in the type of soil cover) can cause environmental impacts, either through the suppression of native vegetation and riparian forests or even through the increase in the use of pesticides, fertilizers and consequent processes of leaching and percolation in the soil that represent potential risks of contamination of water bodies, even more expressively when the aforementioned changes are not accompanied by water quality monitoring programs.The Integrated Management of Water Resources promotes the overcoming of the sectorial and fragmented approach and is foreseen as one of the guidelines of the National Water Resources Plan. In order to be successful, a management plan must include continuous monitoring, enabling the assessment of WRs adjacent to changes in the use and cover of the watershed's land. In the Serrana mesoregion of the state of Santa Catarina, is located the Marombas river hydrographic sub-basin, component of the Canoas River BH, supplying water for industrial supply, irrigation for agricultural crops, agricultural production in addition to public supply for ten municipalities: Lebon Régis, São Cristóvão do Sul, Santa Cecília, Ponte Alta do Norte, Monte Carlo, Curitibanos, Frei Rogério, Brunópolis, Fraiburgo and Campos Novos. The main objective of this work was to evaluate the influence of land cover and land use on surface water quality in the Marombas River sub-basin, using the land cover and land use classification of the study area based on remote sensing, the determination of the Water Quality Index for watercourses and the evaluation of the relationships between land use and water quality through statistical techniques of Principal Component Analysis and Multinomial Logistic Regression. The classification was conducted through a Random Forest algorithm, consisting of a classifier composed of multiple decision trees. The WQI consists of a weighted product of nine parameters associated with water quality: thermotolerant coliforms, pH, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Nitrates, Total Phosphate, Temperature, Turbidity and Total Residue after evaporation. The results regarding the Land Cover and Use Classification indicated that the majority occupation of the Marombas River sub-basin is focused on productive activities linked to agriculture, livestock and forestry, reaching more than 60% of the total land cover. The determined Water Quality Indexes varied between “Good” and “Bad”, maximum value of 78.86 and minimum value of 45.49, demonstrating expressive sensitivity of water bodies to potential polluters present in the sub-basin, presenting values altered thermotolerant coliforms, turbidity and total phosphorus, reducing IQA values in all areas studied throughout the collection campaigns carried out on the Pessegueirinho River, Marombas River, Pedras River and Correntes River.During the analysis period, significant relationships were detected between areas with greater occupation of the land cover/use classes "Agriculture", "Pasture", "Mosaic of Agriculture and Pasture" and "Forestry" with the quality parameters of water pH and turbidity.

Conducting agricultural activities in a conventional way, and its expansion in space and time (change in land use and in the type of soil cover) can cause environmental impacts, either through the suppression of native vegetation and riparian forests or even through the increase in the use of pesticides, fertilizers and consequent processes of leaching and percolation in the soil that represent potential risks of contamination of water bodies, even more expressively when the aforementioned changes are not accompanied by water quality monitoring programs.The Integrated Management of Water Resources promotes the overcoming of the sectorial and fragmented approach and is foreseen as one of the guidelines of the National Water Resources Plan. In order to be successful, a management plan must include continuous monitoring, enabling the assessment of WRs adjacent to changes in the use and cover of the watershed's land. In the Serrana mesoregion of the state of Santa Catarina, is located the Marombas river hydrographic sub-basin, component of the Canoas River BH, supplying water for industrial supply, irrigation for agricultural crops, agricultural production in addition to public supply for ten municipalities: Lebon Régis, São Cristóvão do Sul, Santa Cecília, Ponte Alta do Norte, Monte Carlo, Curitibanos, Frei Rogério, Brunópolis, Fraiburgo and Campos Novos. The main objective of this work was to evaluate the influence of land cover and land use on surface water quality in the Marombas River sub-basin, using the land cover and land use classification of the study area based on remote sensing, the determination of the Water Quality Index for watercourses and the evaluation of the relationships between land use and water quality through statistical techniques of Principal Component Analysis and Multinomial Logistic Regression. The classification was conducted through a Random Forest algorithm, consisting of a classifier composed of multiple decision trees. The WQI consists of a weighted product of nine parameters associated with water quality: thermotolerant coliforms, pH, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Nitrates, Total Phosphate, Temperature, Turbidity and Total Residue after evaporation. The results regarding the Land Cover and Use Classification indicated that the majority occupation of the Marombas River sub-basin is focused on productive activities linked to agriculture, livestock and forestry, reaching more than 60% of the total land cover. The determined Water Quality Indexes varied between “Good” and “Bad”, maximum value of 78.86 and minimum value of 45.49, demonstrating expressive sensitivity of water bodies to potential polluters present in the sub-basin, presenting values altered thermotolerant coliforms, turbidity and total phosphorus, reducing IQA values in all areas studied throughout the collection campaigns carried out on the Pessegueirinho River, Marombas River, Pedras River and Correntes River.During the analysis period, significant relationships were detected between areas with greater occupation of the land cover/use classes "Agriculture", "Pasture", "Mosaic of Agriculture and Pasture" and "Forestry" with the quality parameters of water pH and turbidity.