Groundwater geochemistry of the Chihuahua City region in the Rio Conchos Basin (northern Mexico) and implications for water resources management

Abstract

Abstract:The Chihuahua City region, located in the semiarid-arid northern highlands of Mexico, has experienced intensive groundwater abstraction during the last 40 years to meet water demands in the region. A geochemical survey was carried out to investigate the evolution from baseline to modern conditions of a 130-km flow path including the El Sauz-Chihuahua-Aldama-San Diego de Alcalá regions. The research approach included the use of major chemical elements, chlorofluorocarbons and environmental isotope ( 18 O, 2 H, 13 C and 14 C) tracers. Stable isotopes indicate that groundwater evolves from the evaporation of local rainfall and surface water. Groundwater located at the lower end of the flow section is up to 6000 years old and older groundwater in the order of 9000 years BP was found in a deep well located in the upper part of the flow system, implying contribution from a neighbour basin. The background groundwater chemistry upstream of Chihuahua City results from feldspar weathering. Beyond Chihuahua City the chemical conditions are strongly modified owing to disposal of sewage from public and industrial water supplies into the Rio Chuviscar, subsequent allocation of this water to agricultural irrigation areas and direct infiltration under the river bed. As a consequence, anions like chloride and sulphate are mainly related to surface sources. Nitrate is controlled in part by sewage from public supply and industry and in part by agricultural practices. Arsenic and fluoride are related to weathering of rock formations of local mineralized ranges and subsequent enrichment of the basin-fill by magmatic processes. The results of this study have implications for groundwater management in an arid region that depends entirely on groundwater for domestic, industrial and agricultural water consumption.

A groundwater isoscape (δD, δ18O) for Mexico

“…2007a; Mahlknecht et al, 2006). Only in some specific sub basins and in geothermally impacted groundwaters are evaporative or isotope trends observed due to isotope exchange processes (Cortes et al, 2007;Issar et al, 1984;Mahlknecht et al, 2008;Portugal et al, 2005). Others have noted groundwater infiltrating below reservoirs and lakes and recycled irrigation in Mexico show distinct δD-δ 18 O evaporation trends (Carrillo-Chavez et al, 2003;Horst et al, 2007b).…”

Interaction between deep and shallow groundwater systems in areas affected by Quaternary tectonics (Central Italy): a geochemical and isotope approach

“…Main processes that could be investigated are (1) the evolution of groundwater via water-rock interactions and/ or mixing processes of fluids of different reservoirs and (2) groundwater origin and flowpaths, including interactions of groundwater and surface water. In this paper a multi-isotope approach has been followed, including: radon (Lambs 2004;Corbett et al 1997Corbett et al , 2000Tuccimei et al 2005); oxygen and hydrogen isotopes (Kattan 1997;Izbicki et al 2004;Pizzino et al 2004;Palmer et al 2007;Mahlknecht et al 2008); isotopic composition (O, H, He, C) of gases dissolved in volcanic aquifers (Rose et al 1996;Parello et al 2000;Federico et al 2001) and sulphur isotopes (Berner et al 2002: André et al 2005Jeziersky et al 2006;Garfias et al 2009). …”

Groundwater flow processes and mixing in active volcanic systems: the case of Guadalajara (Mexico)

“…The relation with temperature indicates the recharge conditions at different recharge sites. Factor 4 (PC4; 7 %) may be indicative of the dissolution of minerals that contain F. The study of Sánchez-Díaz (2007) indicates that rhyolitic rocks and ashes of the study area are responsible for releasing F. Comparable trends have been observed in various similar volcanic environments in central and northern Mexico (Mahlknecht et al, 2004a(Mahlknecht et al, , 2008. This factor is associated with MG and HG groups.…”