Composicion quimica y calidad del agua del Rio Castano. Calingasta, San Juan, Argentina.

• Autor: Pittaluga, Mar

RESUMEN

La provincia de San Juan, ubicada en el sector árido del centro-oeste de la República Argentina, es irrigada por dos sistemas fluviales importantes como son, los ríos Jáchal y San Juan. El río Castaño, objeto de este estudio, es uno de los principales tributarios del río San Juan que atraviesa el área minera de Castaño Viejo conocida desde 1863, pero explotada intensamente en el período 1956-1964. En el presente trabajo, se definen algunas características hidroquímicas de este sistema hidrográfico, vinculadas a las actividades mineras enunciadas. El desarrollo del trabajo consistió en un muestreo sistemático del agua del río Castaño para conocer particularmente los niveles de concentración de metales pesados, como cadmio, cinc, cobre, cromo, plomo y aluminio, y determinar su incidencia en la composición y calidad del agua. También se determinaron en laboratorio y campo parámetros tales como: pH, conductividad eléctrica y sólidos disueltos en el agua.

Los resultados obtenidos indican que algunos parámetros químicos del agua de río, están vinculados a las variaciones de caudales provocadas por las diferentes estaciones del año y por el régimen de alimentación nival del río Castaño.

El agua de este sistema hidrográfico no presenta sustancias tóxicas en niveles de contaminación y algunos de los tenores más altos de elementos pesados estarían relacionados con las áreas de afloramientos mineralizados por donde drena el río. Se concluye entonces, que la calidad de este recurso hídrico andino no ha sido afectada por la explotación minera realizada.

Palabras claves: Calidad del agua, Elementos pesados, centro oeste Argentina.

CHEMICAL COMPOSITION AND WATER QUALITY OF THE CASTAÑO RIVER, CALINGASTA, SAN JUAN PROVINCE, ARGENTINA.

ABSTRACT

The province of San Juan, in arid central-west Argentina, is irrigated by two fluvial systems: the Jachal and San Juan River basins. The Castaño River is one of the two main tributaries to the latter. It crosses the Castaño Viejo mining district, which was a producer of lead, zinc and copper.

To investigate the water quality and the possible hydrochemical variations given rise by the mining activity, a sampling net was devised along the river course for determining concentrations of calcium, magnesium, sodium, carbonates, bicarbonates, sulphates, cadmium, copper, chrome, lead, zinc, aluminium, pH, dissolved solids and electric conductivity.

The results obtained indicate that some chemical parameter of the river water vary in the different seasons of the year.

The salinity, dissolved oxygen and biochemical demand of oxygen were found to be low, no toxic substances were detected in significant amounts, and the water quality has not been affected by the mining activity.

Key words: WaterQuality. Heavy elements. Centre West Argentina.

INTRODUCTION

The province of San Juan is situated in the central-western part of the Argentina Republic. It extends from 28[degrees]30, to 32[degrees]30'S and from 66[degrees]30, to 70[degrees]30, W. It covers 93,650 [km.sup.2] in one of the most arid regions in the country: therefore a rational use of surface and ground water is a paramount importance for the life and development of the province.

The province of San Juan, however, is irrigated by two main fluvial systems, namely the Jachal and San Juan river basins. The latter river takes its name at the junction of the Los Patos and Castaño rivers. Both have their catchment basins in the Andean Cordillera and flow into the Calingasta valley.

This valley, situated at about 120 km west of the capital of the province, is a NS trending tectonic depression between the Frontal Cordillera, to the west, and the western Precordillera ranges to the east. The Los Patos river, one of the two main streams in the valley, runs from S to N, whilst the other important river, Castaño, runs from NW to SE. As previously said, both rivers, at their junction (the locality called Las Juntas), form the San Juan river (Figure 1). Its importance derives from the fact that this fluvial system supports the life and development of the Tulum valley, with 450,000 inhabitants.

According to Rodriguez (1985) the ground water...