Evidencias hidrogeoquímicas e isotópicas sobre el origen del agua subterránea en la cuenca hidrográfica Río Actopan, Estado de Veracruz

Abstract

Physical-chemical, chemical and isotopic data of spring water, groundwater and river water from the Actopan basin, central Veracruz were analyzed with the purpose of determining the origin and flow of groundwater. Spring water temperature between 9.6 °C and 18.3 °C, and low electrical conductivity (<150 µS/cm) suggest local recharge. Groundwater temperature of 38.2 °C and electrical conductivity of 1542 µS/cm, 48 mg/L of Cl–, y 721 mg/L of SO42– are associated to deep flow and rock-water interaction (limestone, dolomite, gypsum/anhydrite). Concentrations of NO3– > 10 mg/L allow the identification of anthropogenic sources. Hydrogen and oxygen isotope results fit reasonable well with the Global Meteoric Water Line (GMWL, δ2H = 8 δ18O + 10) indicating that their recharge derives from local precipitation. On the basis of the observed isotope gradient with altitude (Z), (δ18O = -2.1 (Z km) - 5.56), three main groups of groundwater have been identified: 1) Evaporated water related to the precipitation in the dry season; 2) water, located on the line defined for the regional isotopic gradient, recharged during the rainy season; and 3) water recharged at levels slightly higher than its theoretical value of recharge, showing a component of deep flow and recharge from river water in the coastal plain.