The effects of hydraulic works and wetlands function in the Salado-River basin (Buenos Aires, Argentina)

Abstract

Man-made activities exert great influences on fluvial ecosystems, with lowland rivers being substantially modified through agricultural land use and populations. The recent construction of drainage canals in the upper stretch of the Salado-River basin caused the mobilization of huge amounts of salts formerly stored in the groundwater. The main aim of this work was to analyze the effect of the discharges of those canals into the Salado-River water, under different hydrologic conditions, and the role of the wetlands and shallow lakes placed along the canals' system. Physicochemical variables were measured and water samples were taken during times of high water, mean flows, drought, and extreme drought. The environmental variables and the plankton development were related to the hydrologic regime and reached minimum values during floods because of low temperatures and dilution. Local effects on the water's ionic composition became pronounced during droughts because of groundwater input. Nutrient concentrations were mainly associated with point wastewater discharges. Conductivity, ion concentrations, total plankton biomass, and species richness increased in the Salado-River downstream site, after the canals' discharges. The artificial-drainage system definitely promotes the incorporation of salts into the Salado-River basin. In this scenario, a careful hydraulic management is needed to take into account this issue of secondary salinization that threatens the economic exploitation of the region. The wetlands present in this study acted as service environments not only helping to reduce salt, nutrient, and suspended-solid concentrations downstream but also contributing a plethora of species and plankton biomass into the Salado-River main course.

Metal geochemistry in suspended and bed sediments in the eutrophic lowland Salado River basin (Buenos Aires, Argentina)

“…In general, sampling stations were very shallow (< 1.5 m), with highly alkaline (pH: 8.8 ± 0.4), saline (5.2 ± 1.8 mS/cm), turbid (467 ± 237 NTU), eutrophic (Chl a: 187 ± 119 µg/l) and relatively well-oxygenated waters (DO: 9.8 ± 2.1 mg/l). Chl a concentrations were very high and variable (20-439 µg/l; RSD 64%), in agreement with previously published values (5.0-416 µg/l, Gabellone et al 2005;Bazurri et al 2018) corresponding to eutrophic to hypereutrophic waters (Quirós and Drago 1999;Wetzel 2001). Chl a was significantly higher in lakes than in the main course and tributary streams (p < 0.05) with the lowest value at Chivilcoy stream (20 µg/l).…”

“…The high conductivity of Salado River waters (2.8-11 mS/cm) showed no clear spatial trend. The maximum value corresponds to the shallow Bragado lake which receives the contribution of salt-laden groundwaters from the NW endorheic region through artificial drainage channels constructed in the last decades (Bazurri et al 2018).…”

“…The basic hydrochemistry and plankton dynamics of the Salado River have been extensively studied (Gabellone et al 2005(Gabellone et al , 2008Bazurri et al 2018 and references therein), but despite the economic importance of the basin, no comprehensive study on the sources and distribution of pollutants has been yet conducted. To fill this gap, in this study, we analyze the variation of water quality parameters and the spatial distribution of major and trace metals in suspended and bed sediments along the Salado River basin.…”

A review of recent advances and future challenges in freshwater salinization

“…In South America, very high salt loads into the Amazon River have been reported due to oil extraction (Moquet et al, 2014). Also, increases in the salinity of freshwaters have been associated with salt factories (González Achem et al, 2015) and drainage canals (Bazzuri et al, 2018) in Argentina and salt extraction (Akomolafe & Onwusiri, 2017), agriculture (Scherman et al, 2003) and industry (Dikio, 2010) in Africa.…”

Estructura y dinámica del bacterioplancton en cuatro lagunas pampeanas de la cuenca del río Salado (Buenos Aires, Argentina)

“…Por su parte, las lagunas de la Región Pampeana se caracterizan por presentar un grado alto de trofismo natural, y su dinámica está influida en gran medida por las condiciones climáticas e hidrológicas (Gabellone et al 2003;Diovisalvi et al 2015). En los últimos años, el estado trófico de estas lagunas fue variando entre eutrófico e hipereutrófico, con frecuentes floraciones de algas y cianobacterias (e.g., Quirós et al 2002b;Grosman 2008;O´Farrell et al 2019O´Farrell et al , 2021, como consecuencia del desarrollo económico, el crecimiento poblacional y las actividades agrícola-ganaderas que se realizan a sus alrededores (e.g., Bazzuri et al 2018). Por lo general, estos cambios perturban el funcionamiento normal de los ecosistemas acuáticos y afectan a los servicios ecosistémicos tales como el reciclado de nutrientes, el mantenimiento del régimen de descarga de ríos, la recarga de napas subterráneas, la provisión de hábitat para la biodiversidad y las actividades de recreación (Quirós 2000;MEA 2005).…”