Water quality and impacts of development

MENONE MIRTA L.; TEIXEIRA DE MELLO FRANCO

The Paraná River Basin. Managing water resources to sustain ecosystem services.

Routledge- Taylor & Francis Group

Año: 2020; p. 124 - 139

Although the Upper Paraná contributes >50% of the water budget of the river, the largest proportion of transported suspended sediment and organic material is carried into the Middle Paraná from the Paraguay River. Increased sediment load constitutes a stressor and is caused by changes in land-use and land-based pollution. Surface runoff from urban centers constitutes a source of nutrients all along the river, while fish farming and cattle ranching have been contributing nutrients in the Upper and Middle stretches, respectively.Anthropogenic activities are responsible for impaired water quality in the Paraná River Basin. The water quality of the Upper Paraná basin is affected by transport of pesticides from agricultural activities and by discharges from industry. However, the most influential anthropogenic impacts are from the approximately 140 hydroelectric dams and reservoirs. Inputs of nutrients into these reservoirs are causing eutrophication, which is resulting in harmful blooms of cyanobacteria. The Middle and Lower stretches of the Paraná River Basin are affected by discharges of partially treated domestic wastewater and industrial pollution, as well as agricultural activities. High concentrations of metals and metalloids such as Cd, Pb, Cu, F, Ni, Cr and As have been detected in some reaches of the river. While for some of these elements, such as As, natural geochemical processes could be the main source, others originate from the effluents of metallurgical and tannery industries and wastewater discharges from cities. The concentrations of Cd, Pb, Cr, Fe and Mn in sediments often exceed regulatory limits for the protection of aquatic life.Current use of insecticides, the persistent organochlorine insecticide endosulfan and the herbicide glyphosate are ubiquitous in the Paraná River Basin. In the Upper Paraná stretch the main pesticides reported are the insecticides malathion, lambda cyalothrina, endosulfan and the herbicide metolachlor. In the Middle and Lower Paraná stretches, the insecticidescypermethrin and chlorpyrifos and the herbicide glyphosate predominate in surface waters.A recent study reported concentrations of pesticides in water in the basin ranging from 0.004?6.62 μg L-1, with concentrations of some compounds often over the recommended guidelines for the protection of aquatic biota.