Application of stable isotopes and hydrochemistry for the understanding of the hydrological system in Laguna de Tiscapa. Managua, Nicaragua

Abstract

Stable isotopes (Deuterium and Oxygen 18) and hydrochemistry were used as tracers to determine the origin of the water in the crater of Laguna de Tiscapa and its interactions with groundwater and Lake Xolotlán. For this purpose, 253 stable isotope results and 56 hydrochemical results from the sources: precipitation, groundwater, Laguna de Tiscapa, and Lake Xolotlán were used. The stable isotopes indicate that Laguna de Tiscapa is recharged in a western zone by groundwater where there is an average composition of -7‰ inδ¹⁸O, the evaporation processes in the lagoon make it have an average composition of -5.4‰ in δ¹⁸O, reflecting this contribution from Laguna de Tiscapa northeast zone of groundwater with enrichment of -6‰ in δ¹⁸O. The hydrochemical composition in Laguna de Tiscapa has common relation with groundwater where the dissolution processes of geological material and not the meteoric one rule, this dissolution makes HCO^-₃, Ca⁺², Na⁺, Mg⁺² ions predominate.  The dissolution processes are mainly due to the presence of silicates followed by calcites, which is characteristic of the composition of the Las Sierras aquifer. The contribution of water from Lake Xolotán to Laguna de Tiscapa can be excluded, since it has a highly enriched isotopic composition, in addition to the salinization processes experienced by this body of water.