Análise de precipitações médias históricas e decenais para determinação de disponibilidade hídrica, com foco na gestão do abastecimento público de água
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2023-07-03
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Universidade Estadual Paulista (Unesp)
Resumo
Tradicionalmente os diagnósticos de disponibilidade hídrica para abastecimento público de água de municípios, quer seja em aspecto qualitativo ou quantitativo, buscam determinar as vazões características de cursos d’água mediante dos índices médios anuais de precipitação, assim como apurar as vazões demandadas pelos diversos usuários em uma bacia hidrográfica, a qualidade das águas dos mananciais, suas características, tais como fisiográficas, pedológicas, hidrogeológicas, etc; e o modo como é praticado o uso e ocupação do solo, de maneira a identificar os potenciais poluentes gerados em decorrência das atividades antrópicas desenvolvidas na região. Contudo, quanto ao aspecto quantitativo, os estudos relacionados ao uso da água devem considerar um novo componente nas análises de disponibilidade hídrica, qual seja, os efeitos das mudanças climáticas, principalmente em relação às estiagens mais severas e de extensa duração sobre o serviço de abastecimento público. Isto posto, o presente estudo teve por finalidade propor uma metodologia alternativa de determinação e análise de disponibilidade hídrica, considerando, além do tradicional estudo da série histórica, uma avaliação de cenários decenais recentes, em que as precipitações anuais têm registrado acumulados inferiores à média histórica, resultando na redução das vazões de referência. Para composição do estudo por múltiplos cenários, foram colhidos registros oficiais de precipitações mensais de 1970 a 2019, apuradas as demandas de uso de água outorgadas para seis sub-bacias hidrográficas do município de Bragança Paulista; e registros de qualidade dos mananciais eleitos. Partindo dessas informações foram determinadas a precipitação média do município (Método dos Polígonos de Thiessen), as vazões referenciais, o total de demandas por sub-bacia, o balanço entre disponibilidade e demanda, as vazões remanescentes disponíveis para uso e o índice de estresse hídrico de cada sub-bacia hidrográfica. Das seis sub-bacias estudadas foi constatado que apenas duas apresentam vazões remanescentes suficientes para atender a um aumento de demanda para abastecimento público futuro. Ao fim, concluiu-se que a metodologia proposta de análise de múltiplos cenários de precipitação média anual, foi validada como produto a ser aplicado em estudos para determinação de disponibilidade hídrica, não devendo esses estarem limitados à média da série histórica da região estudada.
Traditionally, diagnoses of water availability for public water supply in municipalities, whether qualitatively or quantitatively, seek to determine the characteristic flows of watercourses through average annual precipitation rates, as well as to determine the flows demanded by the various users in a hydrographic basin, the quality of water from springs, their characteristics, such as physiographic, pedological, hydrogeological, etc.; and the way in which the use and occupation of the soil is practiced, in order to identify the potential pollutants generated as a result of the anthropic activities carried out in the region. However, regarding the quantitative aspect, studies related to water use must consider a new component in the analyzes of water availability, that is, the effects of climate change, mainly in relation to the most severe and long-lasting droughts on the supply service. public. That said, the present study aimed to propose an alternative methodology for determining and analyzing water availability, considering, in addition to the traditional study of the historical series, an evaluation of recent ten-year scenarios, in which annual precipitation has registered less than the historical average, resulting in the reduction of the reference flows. For the composition of the study by multiple scenarios, official records of monthly precipitation were collected from 1970 to 2019, the water use demands granted for six hydrographic sub-basins in the municipality of Bragança Paulista were determined; and quality records of the chosen sources. Based on this information, the average precipitation in the municipality (Thiessen Polygon Method), the reference flows, the total demands per sub-basin, the balance between availability and demand, the remaining flows available for use and the water stress index were determined. of each hydrographic sub-basin. Of the six sub-basins studied, it was found that only two have sufficient remaining flows to meet an increase in demand for future public supply. In the end, it was concluded that the proposed methodology for analyzing multiple scenarios of average annual precipitation was validated as a product to be applied in studies to determine water availability, which should not be limited to the average of the historical series of the studied region.
Traditionally, diagnoses of water availability for public water supply in municipalities, whether qualitatively or quantitatively, seek to determine the characteristic flows of watercourses through average annual precipitation rates, as well as to determine the flows demanded by the various users in a hydrographic basin, the quality of water from springs, their characteristics, such as physiographic, pedological, hydrogeological, etc.; and the way in which the use and occupation of the soil is practiced, in order to identify the potential pollutants generated as a result of the anthropic activities carried out in the region. However, regarding the quantitative aspect, studies related to water use must consider a new component in the analyzes of water availability, that is, the effects of climate change, mainly in relation to the most severe and long-lasting droughts on the supply service. public. That said, the present study aimed to propose an alternative methodology for determining and analyzing water availability, considering, in addition to the traditional study of the historical series, an evaluation of recent ten-year scenarios, in which annual precipitation has registered less than the historical average, resulting in the reduction of the reference flows. For the composition of the study by multiple scenarios, official records of monthly precipitation were collected from 1970 to 2019, the water use demands granted for six hydrographic sub-basins in the municipality of Bragança Paulista were determined; and quality records of the chosen sources. Based on this information, the average precipitation in the municipality (Thiessen Polygon Method), the reference flows, the total demands per sub-basin, the balance between availability and demand, the remaining flows available for use and the water stress index were determined. of each hydrographic sub-basin. Of the six sub-basins studied, it was found that only two have sufficient remaining flows to meet an increase in demand for future public supply. In the end, it was concluded that the proposed methodology for analyzing multiple scenarios of average annual precipitation was validated as a product to be applied in studies to determine water availability, which should not be limited to the average of the historical series of the studied region.
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Gestão de Recursos Hídricos, Segurança hídrica, Suficiência hídrica, Plano Municipal de Saneamento Básico, Water Resources Management, Water security, Water sufficiency, Municipal Basic Sanitation Plan