Origin and hydrochemical characteristics of groundwater in the Northeastern Patagonia, Argentina: the relationship with
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THEMATIC ISSUE
Origin and hydrochemical characteristics of groundwater in the Northeastern Patagonia, Argentina: the relationship with geomorphology and soils María del Pilar Alvarez1,2 · Daniela Funes3 · Cristina Dapeña4 · Pablo José Bouza1 Received: 14 May 2020 / Accepted: 12 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In arid zones, geomorphology and soils play a fundamental role in groundwater surveys as they condition the recharge phenomenon and some processes that modify water chemistry. The objective of this work was to identify the groundwater provenance and the relationship between its chemistry and isotope contents with the geomorphology and soil in the northeastern Patagonia, Argentina. Over an area of 10,600 km2, groundwater levels and major ionic and stable isotopic contents were measured. The main geomorphological units were mapped using satellite images and digital elevation models. In soils, pedogenetic carbonate contents (PC) and clay accumulation index (CAI) were measured. Different hydrochemical facies were identified in relation to geomorphological units, being the Cl–SO4–Na and Cl–Na ionic types dominant in fluvial terrace plains (terrace associations, TAs). The Cl–SO4–Na types are the most saline groundwaters and are coincident with the TA where Petrocalcids are the dominant soils. With less salinity contents, Cl–SO4–Na and Cl–Na types are the groundwaters associated with TA where the dominant soils are Natrargids and Haplocalcids. The only sector with Cl–HCO3–Na is those with fresh water coincident with the Aeolian field unit, where Psamments soils develop. Likewise, groundwater is isotopically differentiated in response to the origin being mostly allocthonus in the fluvial terrace plains and from local recharge in the Aeolian fields. The fluvial terraces are gravel deposits that would favor a local recharge, but this is prevented both by pedogenic carbonate and clay contents which developed in the upper part of the deposit. In this way, the measurement of pedogenetic carbonates and clays becomes soil properties of utmost importance to be considered in groundwater prospecting in arid regions worldwide. Keywords Stable isotopes · Hydrochemistry · Pedology · Geomorphological units · Chubut province
Introduction This article is a part of the Topical Collection in Environmental Earth Sciences on “Advances in Environmental Geochemistry” guest edited by Dr. Eleanor Carol, Dr. Lucia Santucci and Dr. Lia Botto. * María del Pilar Alvarez alvarez@cenpat‑conicet.gob.ar 1
Instituto Patagónico para el Estudio de los Ecosistemas Continentales (IPEEC-CONICET), Puerto Madryn, Argentina
2
Universidad Nacional de la Patagonia San Juan Bosco (UNPSJB), Puerto Madryn, Argentina
3
Centro de Investigaciones Geológicas (CIG-CONICET), La Plata, Argentina
4
Instituto de Geocronología y Geología Isotópica (INGEIS, CONICET-UBA), Buenos Aires, Argentina
One third of the earth’s surface is occupied by arid regions, with annual precipitations between 25 and 25
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