IADO   05364
INSTITUTO ARGENTINO DE OCEANOGRAFIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Freshwater influence on the Coastal Zone management. Bahía Blanca estuary (Argentina) as a study case.
Autor/es:
FABIANA LIMBOZZI; HUGO FREIJE,; JORGE MARCOVECCHIO
Lugar:
Foz de Iguaçú
Reunión:
Congreso; 2010 The Meeting of the Americas – AGU (American Geophysical Union); 2010
Institución organizadora:
American Geophysical Union
Resumen:
The results on the input of both surface and groundwater into Bahía Blanca estuary are presented, put them on the framework of the estuarine water quality and the Coastal Zone Management. So, the main existing pressures were evaluated, analyzing the state of the water quality within the catchments of both rivers outleting into the estuary: Sauce Chico river and Napostá Grande Stream. The DPSIR approach has been applied to developed the mentioned assessment. Different quantity indicators have been identified through the study. Thus, while the piezometric level has been proposed as the indicator for groundwater, the rivers discharge flow into the estuary was for the surface ones. On the other hand, water quality indicators represent the effects of pressures originated by changes in soil uses directed to both urban develope of the city and industrial activity within the Coastal Zone. State indicators used to determine the effects of rivers discharge on the estuary were: nitrate, ammonium, phosphate, silicate, dissolved oxygen, conductivity, chloride and pH ; in addition, data on BOD, COD and fecal coliform occurrence in surface waters are also reported. The study allowed to confirm the effect of pressures on the quality state of groundwater and surface ones within both considered catchments. The Napostá Grande Stream has shown the effect of these pressures upstream and downstream of the city of Bahía Blanca, including low variations in conductivity and silicate levels, as well as significant increases in nitrate concentrations (even did not exceed the standards recommended by WHO for drinking water). Moreover, Sauce Chico River showed low levels of phosphate, ammonium and nitrate in the down basin, where intensive agricultural practices are developed. Dissolved oxygen and chloride levels have recognized as normal within both catchments. Napostá Grande watershed’s groundwater presented and increasing of salinity downgradient due to a salt enrichment linked to evaporation, with a maximum value in the discharge within the Coastal Area. Conductivity does not show significant changes respect to values reported during the 90; however these higher values give a high potential risk of salinization for agricultural activities. Nitrate presented the highest values on the high basin, presumably related to poor farming practices. The ion concentrations at the Sauce Chico Basin also show a tendency to increase from the recharge area to discharge one into the estuary, presenting low hydraulic gradients and low permeability of sediments, which promote evapo-transpiration and vertical infiltration compared with the horizontal flow of groundwater. At present the piezometric levels show no change with regard to those obtained on the late 80s. It concludes that it is necessary to take steps towards controlling the main pressures in the region caused by the discharge of wastewater from Bahia Blanca, by pollution from farming and industrial area located in the coastal region to obtain an improvement in the quality of inland waters and those of the estuary.