Abstract
In view of the complexity of the processes associated to water quality, this study objective is to identify the main factors related to spatial and seasonal variability in water courses of the Lobo Stream River Basin. To this, multivariate statistical techniques were used. Data collection for water quality and streamflow variables were carried out monthly, from May 2018 to April 2019, at 10 monitoring points along basin's tributaries. The results show that, during the dry season, the main causes for water quality decrease are related to erosion process on the river margins, which is intensified by inadequate handling in livestock activities in some monitoring points. In the rainy season, the main causes are related to soil leaching in agricultural areas that increases the nitrogen compounds concentration and reduces water quality. However, in addition to this, it was noted that regardless the environmental conditions, the most impactful factor is the point pollution from the effluent discharge of Itirapina City sewage treatment plant, responsible for nutrient concentration increase, organic contamination, OD reduction, and, consequently, water quality deterioration. With this, the study shows how multivariate statistical analysis enables more relevant evaluation of water quality data variability and supports further studies in the basin.
Highlights
The maintenance of social, economic and ecological systems depends on the availability of natural resources, especially water, which is essential for the existence of life
The increase in population, human activities, and demand for water, as well as inappropriate land use and climate change, are the main factors responsible for changes in water resources, which can compromise aquatic ecosystems and socioeconomic sectors that depend on services ecosystems provided by them (Tundisi et al 2015, Bai et al 2019, Pham et al 2019)
Differences in data behavior can be observed between the monitoring points
Summary
The maintenance of social, economic and ecological systems depends on the availability of natural resources, especially water, which is essential for the existence of life. Water availability and quality are being threatened due to human activities that generate multiple pressures, such as the dumping of domestic waste, hydromorphological changes, diffuse pollution of agricultural areas and drainage of urban areas that can pollute water bodies and change their ecological status (Grizzetti et al 2017, Zhao et al 2018, Mello et al 2020). The increase in population, human activities, and demand for water, as well as inappropriate land use and climate change, are the main factors responsible for changes in water resources, which can compromise aquatic ecosystems and socioeconomic sectors that depend on services ecosystems provided by them (Tundisi et al 2015, Bai et al 2019, Pham et al 2019). The rainfall conditions and the type of land use can affect the flow regime of rivers as well as the transport and dilution of pollutants, which can affect water quality
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