A Multidisciplinary Approach for Clarifying the Recharge Processes and Origin of Saline Water in the Semi-Arid Punata Alluvial fan in Bolivia

Abstract

The analysis of stable isotopes assisted in identifying that groundwater in the Punata alluvial fan is mainly recharged by heavy flash floods, and the recharge from rainfall is of less importance. In addition, the hydrochemical analysis identified the Pucara River as the main source of recharge. Other streams in the north and northwest of the fan do not seem to contribute to the recharge. The hydrochemistry also shows that there is an increase of the Na + and Cl − concentrations in the middle and distal part of the fan. The salinization of groundwater is most likely a result of the mixing of fresh water with residual saline pore water in the lacustrine deposits and/or ion exchange within these layers. Geophysical surveys assisted in describing the aquifer system layering, and indicated a fine-grained bottom layer where ion exchange might occur. This study demonstrates that the integration of several methods (e.g., hydrochemistry, hydrogeophysics, and stable isotopes) is valuable for clarifying ambiguities during the interpretation process and for characterizing hydrogeological processes in alluvial fans in general.

Key hydrological processes in the Del Azul Creek basin, sub-humid Pampean Plain

“…Previous studies have addressed conventional hydrological scenarios featured by slopes greater than 0.5%, with well-defined basin boundaries and drainage networks. Most of these studies have focused on the identification of water recharge sources (Yin et al, 2011;Boukhari et al, 2014;Farid et al, 2014;Gonzales Amaya et al, 2018;Ma et al, 2018;Oiro et al, 2018;Barberá et al, 2018;Bahir et al, 2019); the estimation of aquifers recharge/discharge and water evaporation rates (Mayr et al, 2007;Yuan et al, 2011;Qian et al, 2014); the study of the effect of seasonal rainfall patterns on the isotopic composition of surface water and groundwater (Bajjali, 2006;Dogramaci et al, 2012;Hoke et al, 2013;Singh et al, 2013;Peng et al, 2015;Jódar et al, 2016;Bershaw and Lechler, 2019); and the study of the interactions between surface water and groundwater (Oyarzún et al, 2016;Wu et al, 2017).…”