Hidrogeoquímica de un sistema de la región semiárida: el río Suquía, Córdoba, Argentina.

GAIERO, DIEGO

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentina

Año: 1999 p. 159 - 166

Abstract. Hidrogeochemistry of a semiarid system, Suquía River, Córdoba, Argentina. II. Transport of dissolved solids, weathering, and CO2 consume. The Suquía River occupies a medium size drainage basin (7,700 km2), in the semiarid (800 mm of rainfall per year) region of central Argentina. Over 130 water samples have been analyzed, collect The Suquía system has been studied in detail with the purpose of probing into aspects of the geochemistry of semiarid rivers. ed in different sectors and during different seasons. Through mass transport calculations it has been possible to estimate the annual dissolved load supply to Mar Chiquita Lake in 234,000 t, equivalent to about 30 t km2 a-1. It has been estimated, as well, that about 14% of the dissolved load is supplied to the drainage basin through atmospheric paths. The effect of human activities in the basin increases the TDS production in 122,000 t a-1, roughly 52% of the total dissolved load introduced into Mar Chiquita Lake. The total chemical denudation which is attributable only to the rocks in the Suquía River drainage basin, reaches 10 t km2 a -1, whereas it reaches 28 t km2 a-1 in the upper catchment of the system. This latter value is close to the denudation index found by Garrels and Mackenzie (1971) for South America. The relief is, undoubtly, the most significant variable which controls the geochemistry of the system. Steeper slopes generate lower TDS values. As a first approximation it could be stated that each liter of water supplied by the upper drainage basin neutralizes 0.675 mmol of CO2. If this value is compared to the one calculated by Garrels and Macknezie (1971) for South America (0.29 mmol l-1) it becomes evident the alkaline nature of  the upper drainage, possibly through weathering reactions. Following the approach of Stallard and Edmond (1983) the "transport limited" regime would be the dominating one in a semiarid climate. However, the relief would define distinctive characteristics among the different environments identifiable in the Suquía River.