Mixing of groundwaters with uncertain end-members: case study in the Tepalcingo-Axochiapan aquifer, Mexico

Abstract

Groundwater geochemical data from the northern portion of the Tepalcingo-Axochiapan Valley, in the state of Morelos, Mexico, are analyzed to improve the conceptual hydrogeologic model of the region. The geochemical data suggest that the chemical composition of groundwater is the result of a mixing process between two end-members represented by groundwater from an upper aquifer composed of volcanic-sedimentary rocks and groundwater from a lower aquifer composed of carbonate rocks. Analysis of published data demonstrates that the chemical composition of at least one of the endmembers varies significantly in time. Mixing ratios are computed, taking into account the uncertainty in identifying end-members and the time variability in their chemical composition, using published methods. Computed mixing ratios suggest there is a significant contribution from the lower aquifer to the water pumped by the wells in the area, which should be taken into account in the conceptual hydrogeologic model of the region.

Hydro-chemical evolution of groundwater and mixing between aquifers: a statistical approach based on major ions

“…recharge, reaction and mixing). However, in some situations, mixing can explain the leading order variability in geochemical composition, while chemical reactions explain the remaining variability (Laaksoharju et al 1999(Laaksoharju et al , 2008Morales-Casique 2012).…”

“…Understanding the mixing between groundwater and other water bodies is an important work for groundwater management, because it is a common phenomenon and important process governing groundwater chemistry in many natural systems, and a large number of studies have been processed (Schramke et al 1996;Johannesson et al 1997;Laaksoharju et al 1999Laaksoharju et al , 2008Rueedi et al 2005;Long and Valder 2011;Valder et al 2012;Morales-Casique 2012). Among these studies, geochemistry is considered to be a useful tool in hydrogeological assessment, particularly in constructing a conceptual model of a hydrogeological system.…”

Occurrence and fate of emerging contaminants in urban groundwater. A case study : Barcelona

“…This approach identifies mixing ratios in the case of uncertain end-members and it uses the concentration of mixed samples to reduce the uncertainty, assuming that the samples are a mixing of the end-members in an unknown proportion. This code was previously used to study evaluate mixing processes either in surface water such as rivers (Cánovas et al, 2012a andGalván et al, 2012) and in groundwater (Vàzquez-Suñé et al, 2010;Jiménez-Martínez et al, 2011;Morales-Casique, 2012;Jurado et al, 2012a and.…”

“…. This code was previously used to study evaluate mixing processes either in surface water such as rivers (Cánovas et al, 2012a andGalván et al, 2012) and in groundwater (Vàzquez-Suñé et al, 2010;Jiménez-Martínez et al, 2011;Morales-Casique, 2012;. S2 (Annex I).…”

Mixing and speciation algorithms for geochemical and reactive transport problems

“…Mixing models have been used for decades in many branches of Earth Sciences, including mineralogy (Langmuir et al, 1978), air quality studies (De Gouw et al, 2005) and weathering processes study (Blum et al, 2002). They are also used in a variety of hydrogeological problems, e.g., for quantifying interactions between groundwaters and/or surface waters (Gómez et al, 2014;Morales-Casique, 2012;Kalbus et al, 2006), for determining the proportions of various pollution sources in waste streams (Phillips and Gregg, 2003), for identifying the sources of recharge (Vázquez-Suñé et al, 2010) or hydrochemical and microbiological reactions in urban groundwater (Jurado et al, 2015(Jurado et al, , 2013Tubau et al, 2014), or for assessing water-rock interactions (Daniele et al, 2013;Van der Kemp et al, 2000) or seawater intrusion dynamics (Han et al, 2014;Currell and Cartwright, 2011;Saravana Kumar et al, 2009;Bouchaou et al, 2008;Jørgensen et al, 2008;Walraevens et al, 2007) in aquifers.…”