Water chemistry in Somún Cura region, Rio Negro and Chubut Provinces, Argentina.

CLAUDIO A. PARICA; M. B. REMESAL

Hamburgo

Congreso; 25Latin-American Colloquium og Geosciences; 2019

Universitát Hamburg

The Somún Curá Magmatic Province it is conformed byvolcanic and subvolcanic rocks and extends for 25.000km2 at South centre of Río Negro Province and Northcentre of Chubut Province in Argentine Patagonia. Theentire region under study belongs to a desert regime underextreme temperatures, -25ºC in wintertime to 45ºCin Summer time, with averages between 3ºC to 35ºC withvery dry conditions. The rainy season is springtime with50 mm to 225 mm/year. The evaporation/transpirationis higher than rains during all the year. lsotopically thewater can be divided in four different groups, one forthe north, one for the south with an Atlantic origin ofprecipitations and two small groups with a local signature(Parica et al. 2012; Parica et al. 2017; Remesal et al.2017).lf the rains are present in the system the main sourceof water are located in the high regions (Alta Sierra deSomún Curá, Apas, Talagapa, Sierra Negra de Telsen, etc)after snow melting, water transit occurs through thestructures in the Plateau rocks forming. Sorne salinizationmay occur during this transit and increasing of temperaturestoo from upper to lower levels. Surface water isdriven through streams, the most important are Valcheta(Rio Negro Province) and Telsen (Chubut Province). lntothe basaltic plateau water ci rculation has place throughthe structures, from the upper levels by snow melting tolower levels, where the water get salts and temperatures(23º C for southern water outlets and 45ºC for northernwater outlets).Water chemistry have a narrow spread, the chemistryof water let to classify them into Calcium Chloride, CalciumSulphate and Calcium Bicarbonate, with light sa linizationindex, weak mineralization. No As was detected atthe localities sampled, with pH between 7.4 to 8.4 theseare mainly drinkable waters considering chemistry featuresand low sa linization risks in soils (SAR index).