Trend analysis of water quality in some rivers with different degrees of development within the São Paulo State, Brazil

Abstract

Time series of dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrate, total phosphorus, chloride, ammonia and faecal coliforms (FC), monitored by CETESB ('Companhia de Tecnologia de Saneamento Ambiental'), in the period from 1979 to 2001, were analysed in seven river basins located in the São Paulo State, one of the most developed regions in Brazil. The selected rivers, Piracicaba, Mogi-Guaçu, Turvo Grande, Peixe, Aguapeí, São José dos Dourados and Alto Paranapanema have different degrees of development concerning industrial, agricultural and population growth. Trend analysis methodology was based on graphical exploratory analysis followed by confirmation through statistical tests. Results showed impoverishment of the water quality conditions in most of the studied basins, represented by the positive trends of the parameters (BOD, nitrogens, total phosphorus, clorate and FC) and negative trend of the parameter (DO). Among the analysed basins, the Piracicaba River is the most severely affected with higher variations in the magnitude followed by the basins of the Mogi-Guaçu, Turvo Grande, Peixe and Aguapeí Rivers. On the other hand, the Alto Paranapanema and São José dos Dourados basins are the least affected.

Water Use in Sugar and Ethanol Industry in the State of São Paulo (Southeast Brazil)

“…For instance, according to Dedini S/A [32], a company devoted to building sugar and ethanol industrial plants, technology that allow mills to generate water extracted from sugarcane is already available and can potentially decrease the consumptive use of water by sugarcane mills to almost zero. This gain in water use efficiency is especially important because most of the water is withdrawn by the sugarcane industry from 1st order streams and small rivers (Figure 1), which are already under intensive pressure due to the heavy loads of untreated domestic sewage [33][34][35], and increasing non-point sources of pollution from agricultural [36,37].…”

Impact of Population Growth on the Water Quality of Natural Water Bodies

“…Further, many studies have found untreated sewage to be the most critical issue with respect to water contamination, because 40% of the global population do not have adequate sanitary facilities [5,6]. Changes to land use, land cover or river basins in watershed areas, such as high scale agricultural activities, unplanned infrastructure developments, and sand mining, change the water quality and water balance due to human activities.…”

“…Furthermore, the contents of untreated disposal or spatial disposal items such as organic materials, salinization, nutrients, suspended sediment, enteric virus, and oil and grease are directly affecting the water quality in river basins [7,8]. Furthermore, the aquatic chemical composition is possibly influenced by human activities [6]. This may be caused by improperly planned urbanization or uncontrolled development [9].…”

Water Quality Changes during Rapid Urbanization in the Shenzhen River Catchment: An Integrated View of Socio-Economic and Infrastructure Development

“…It is well known that population growth and industrial activities are drivers of water quality change. Groppo et al [10] found that population growth and increases in untreated sewage were the main causes of water quality deterioration in rivers in the State of Sao Paulo, Brazil. Ma et al [11] found that sharp increases in industrial pollution and domestic discharge were the major causes of water quality deterioration in the Shiyang River, Northwest China.…”

“…Many researchers found that such deterioration is due to the complex interaction between engineered infrastructures and social, economic, legal, and political issues during rapid urbanization [16,17]. However, most research addressed water quality change in urbanized areas rather than catchments in the process of rapid urbanization [6,10]. Furthermore, even fewer studies have investigated the integrated impact of socio-economic and infrastructure development on changes in water quality [16].…”