ORIGINAL ARTICLE Application of chemometrics to hydrochemical parameters and hydrogeochemical modeling of Calera River basin in the Northwest of Argentina M. Rodrı ´guez 1 • A. Sfer 2 • A. Sales 1 Received: 22 April 2015 / Accepted: 26 November 2015 / Published online: 15 March 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract A chemometric study on physico-chemical variables of Calera River basin waters located to the northeast of the province of Tucuma ´n, Argentina was car- ried out. This underground resource is an important alter- native for water supply, and agricultural and cattle activities in this area. A physico-chemical analysis of 44 (forty-four) underground and Calera River water samples was carried out. Chemometric tools were used to determine which variables are more relevant and their possible associations, and also to identify the drillings whose waters are more representative of the area under study. Principal Component Analysis (PCA) and Cluster Analysis (CA) were applied for this purpose. The PCA allowed us to establish that the most important variables in this region are bicarbonate, sulfate and sodium. These ions are the main constituents of the minerals and rocks which form the geological structure of this region since there are limestone deposits (calcium carbonate), gypsum (calcium sulfate dihydrate) and halite (sodium chloride) irregularly distributed all over the region. Besides, an association between bicarbonate with sodium and sulfate with calcium variables was determined by means of CA. The most representative wells of the region under study were also selected by applying PCA. Based on these data, a regional hydrogeochemical model considering the chemical characteristics of waters and their possible interactions with the environment in which they circulate was carried out. The dissolution and/or hydrolysis of min- erals present in rocks were established as important chem- ical processes in the area. Keywords Hydrochemistry Á Chemometrics Á Multivariate analysis Á Water and environment Introduction Calera River basin is located to the northeast of the pro- vince of Tucuma ´n, Argentina, with about 460 km 2 surface. It is part of the hydrogeological basin of the Eastern plain of Tucuman with an area of about 17,000 km 2 . Calera River and its tributaries contain a low mean annual flow, therefore, the underground resource is an important alternative for water supply in this area. There is a significant human settlement distributed all along the basin whose main economic activity is based on agriculture and cattle. Calera River is a typical mountain river that flows between Sierra the Medina and Sierra de La Ramada. There are hills from the tertiary period with a quaternary cover which are located to the southeast of the area (Fig. 1). The geology of the area displays a lithological hetero- geneity with an upper Precambrian and lower Cambrian low degree metamorphic basement associated with lower to middle Cretaceous outcrops with sandstones and con- glomerates that represent the core of Sierra de La Ramada and Sierra de Medina. This stratigraphic arrangement is unconformable and followed by the Tertiary lacustrian strata of the Rı ´o Sali Formation that is represented by medium to fine sandstones that are followed by shales and & A. Sales amsales00@gmail.com M. Rodrı ´guez monanni@fbqf.unt.edu.ar 1 Faculty of Biochemistry, Chemistry and Pharmacy, Institute of Analytical Chemistry, National University of Tucuma ´n, Ayacucho 471, CP 4000 S. M. de Tucuma ´n, Argentina 2 Department of Mathematics, Faculty of Exact Sciences, National University of Tucuma ´n, Av. Independencia 1800, CP 4000 S. M. de Tucuma ´n, Argentina 123 Environ Earth Sci (2016) 75:500 DOI 10.1007/s12665-016-5328-8