Urban stormwater runoff is an important source of pollution in receiving water bodies, mainly in cities in development. However, strategies to deal with the impacts caused by the runoff discharges, such as implementing a sustainable urban drainage system (SUDS) with optimized management, need information usually obtained through monitoring studies. Brasília is a city that has one of the highest urban growth rates in Brazil, with significant impacts on urban water resources, including diffuse pollution, generated by new unregulated urban developments that initially start being built with precarious sanitation infrastructure. The Vicente Pires (VP) watershed is highly urbanized and comprises two areas that have been intensively occupied more recently, at a fast pace, and do not have yet basic sanitation systems fully implemented. Stormwater quality at the outlet of the VP watershed was analyzed by monitoring the rainfall, runoff flows, and pollutant concentration. Event Mean Concentration (EMC) and first-flush (FF) phenomenon were calculated, and hydrologic characteristics were compared for different events through correlation analysis. During dry periods the flow varied between 0.5 and 1.29 m³/s, while in flood periods the maximum value was 72.17 m³/s, forming floods with great volume. Nitrate during dry periods stands out with its high concentration; the maximum was 1.49 mg/L, while the maximum concentration during the flood events was 0.43 mg/L, probably due to dilution. Ammonia results showed very low values, probably because nitrification is occurring up to the collection point. The EMC values of solids in flood events were higher and can be attributed to river bed scour along the VP watershed. The EMC SS values for the VP watershed are also similar to areas in the initial stages of building development. The EMC values in the dry season indicate strong correlations between some water quality parameters such as NH⁺³-N and SS, TS and NO₋₃-N; NO₋₃-N, and COD. These correlations indicate that these pollutants are probably being generated by the same source, probably sewage discharges. During flood events, the correlation between pollutant loads and peak flow can be associated with the scouring during surface washing off, because greater concentrations of solids and organic matter occur in events with greater flow rates. For the first 30% of the initial runoff volume, about 29% of SS, 38% of NH⁺³-N, and 35% of reactive P were carried during flood events. It was verified that large values of maximum or mean rainfall intensity are related to the occurrence of First Flush (FF) for most pollutants. Antecedent dry days (ADD) did not influence build-up processes in this watershed; however, they are related to FF occurrence. Data indicate that the sewage and stormwater collection networks were being installed caused a high impact on observed water quality, with high concentrations of solids during flood events. On the other hand, the wastewater collection after the sewer network installation led to a decrease in COD concentrations over time. For sustainable management of diffuse pollution, the adoption of distributed SUDS to enhance runoff volume reduction is a recommended solution for the case.

Diffuse pollution loads are crucial information for water resource management, and yet field data are often scarce, implying questionable accuracy in load estimates made from low-frequency water quality monitoring. This paper aimed to characterize diffuse pollution in a stream of a mixed-land-cover watershed with a significant portion of urbanized areas through intensive monitoring and to perform a comparative analysis between the loads estimated by pollutant rating curves obtained by regression and the estimates using monthly water quality data, which is the method currently used. Continuous rainfall and flow monitoring was conducted between 2019 and 2021, and samples were collected during flood events and the dry period for water quality analysis. Flood events were found to induce an increase in suspended solids (TSS) and COD concentrations, while inorganic nitrogen (Inorg-N) concentrations were higher in the dry season. Flood characteristics showed a positive correlation with solids and COD event mean concentrations (EMCs) and negative with Inorg-N EMCs, while rainfall characteristics, such as antecedent dry days and intensity, correlate positively with all these pollutants. The rating curves performed well for total load estimation in low discharge events (R² and NSE > 0.8), except for total phosphorus (TP) loads. Estimated annual unit loads found for the watershed were 2 ton TSS/ha.year, 300 kg COD/ha.year, 5 kg Inorg-N/ha.year, and 0.5 kg TP/ha.year, showing high pollution generated in the watershed. Finally, a comparison with estimates based on monthly monitoring data indicated that this method is sufficient for accurate nutrient loads, but not for TSS and COD loads, which require continuous monitoring to improve the accuracy of estimation.

O presente artigo tem o objetivo de analisar como os processos de expansão urbana impactam a sociedade e o meio ambiente, investigando interferências na drenagem de águas pluviais. Tem como estudo de caso o Projeto de expansão urbana do SHTQ - Setor Habitacional Taquari, também conhecido como Serrinha do Paranoá, em Brasília. Tem motivação justificada pela lacuna na literatura no que diz respeito a relacionar aspectos de crescimento urbano com o escoamento superficial. A análise foi feita com emprego da abordagem metodológica da Socioecologia, aquela que analisa criticamente as interações entre o homem e recursos naturais. Os resultados indicam aumento de até 165% na vazão máxima pelo cálculo simplificado, e de 98 % por meio de simulação hidrológica do modelo SWMM, caso a urbanização seja feita nos moldes do projeto elaborado pela Administração Pública. Os resultados demonstraram que o uso das soluções de baixo impacto como biovaletas representa diminuição da vazão máxima de escoamento, com ganhos para a produção das águas.

Entre fevereiro de 2018 e janeiro de 2020, foi realizado o monitoramento hidrológico e de qualidade da água do Córrego Vicente Pires, localizado em uma zona urbana do Distrito Federal, a fim de avaliar as alterações na qualidade da água a partir da determinação de parâmetros físico-químicos, em eventos nos períodos seco e chuvoso. Foram elaborados polutogramas para os parâmetros de condutividade (elétrica), turbidez, pH, sólidos, demanda química de oxigênio e nutrientes (nitrogênio e fósforo), associados aos hidrogramas dos mesmos eventos, com vazões variando de 0,5 m³/s a 72,2 m³/s. O monitoramento dos eventos de cheia obteve concentrações de sólidos totais de até 7.583 mg/L, fosfato até 0,9 mg/L de PO43 e demanda química de oxigênio de até 958 mg/L. No período de estiagem, devido à menor disponibilidade de água no córrego, não há diluição de poluentes e ressalta-se a concentração de nitrato (NO3até 9 mg/L) em função dos lançamentos de esgotos domésticos no córrego. No período chuvoso, evidenciam-se os sólidos totais associados à lavagem da superfície e erosão do solo por grandes volumes gerados no escoamento superficial. Esses resultados expõem a necessidade de investimentos em infraestrutura de coleta de esgoto e drenagem urbana, inclusive, na adoção de medidas de contenção de sedimentos durante a realização de obras.Palavras-chaves: Monitoramento hidrológico; Polutograma; Cheias. URBAN WATERQUALITY IN THE VICENTE PIRES STREAM – FEDERAL DISTRICTAbstractBetween February 2018 and January 2020, hydrological and water quality monitoring of Vicente Pires Stream, located in the urban area of the Federal District, was carried out in order to assess the changes in water quality from the determination of physical-chemical parameters during events in the dry and rainy periods. Polutographs were prepared for parameters such as (electric) conductivity, turbidity, pH, solids, chemical oxygen demand and nutrients (nitrogen and phosphorus), associated with hydrographs of the same events, with flows that ranged from 0.5 m³/s to 72.2 m³/s. The monitoring of flood events showed concentrations of total solids up to 7,583 mg/L, phosphate up 0,9 mg/L PO43 and chemical oxygen demand up to 958 mg/L. During the dry season, due to the lower availability of water in the stream, there is no dilution of pollutants and the nitrate concentration stands out (NO3 up to 9 mg/L), due to discharges of domestic sewage into the stream. In the rainy season, the total solids associated with the washing of the surface and soil erosion by large volumes of runoff stand out. These results expose a need for investment in sewage collection and urban drainage infrastructures, including the adoption of sediment containment measures during the execution of construction.Keywords: Hydrological monitoring; Polutograph; Floods.

A precipitação representa a entrada de água na bacia hidrográfica e determinar sua distribuição espacial é uma atividade complexa visto que o monitoramento é realizado, em geral, de maneira pontual. Dessa forma, torna-se necessária a utilização de métodos de interpolação dos dados para uso em simulação hidrológica. Neste trabalho, foram avaliados 2 eventos de chuva distintos, ocorridos na bacia do Riacho Fundo, no Distrito Federal (DF), no período chuvoso entre 2019 e 2020, com respostas similares de vazão no exutório da bacia. Foram utilizados dados de monitoramento de chuva e vazão provenientes de 14 pluviógrafos e 1 linígrafo de pressão. A interpolação espacial permitiu verificar que os dois eventos de chuva tiveram comportamentos espaciais distintos, evidenciando que o hidrograma no exutório não é suficiente para explicar a chuva na área da bacia. As simulações, realizadas no Storm Water Management Model (SWMM) utilizando as chuvas médias calculadas pelos polígonos de Thiessen, para a área total da bacia e para as sub-bacias resultantes da divisão da área, mostraram a influência da discretização espacial da chuva por sub-bacia quando comparado à consideração de precipitação média para toda a área. Dessa forma, constata-se que a obtenção de dados de entrada para simulações em modelos de chuva-vazão requer a existência de monitoramento extensivo da chuva na bacia, mesmo para bacias relativamente pequenas como a estudada (213 km²).