Caracterización física y química de la Laguna Hule para la estimación preliminar de su conectividad hidrológica con el sistema subterráneo aledaño a la depresión Hule
Fecha
2024
Autores
Montealegre Viales, Emanuel
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Editor
Universidad Nacional (Costa Rica)
Resumen
Resumen. La Laguna de Hule, es una laguna de origen volcánico ubicada en el área protegida del Refugio Nacional de Vida Silvestre Bosque Alegre, aproximadamente a 11 km al norte del Volcán Poás. Esta junto con las lagunas de Bosque Alegre y Congo, forman el complejo conocido como la Depresión de Hule. Estudios previos de esta laguna, han revelado ambientes anóxicos en un rango de 8 m a 10 m de profundidad debido a la oxidación de hierro y la producción de ácido sulfhídrico. Además se ha determinado, diferentes procesos de mezclado en las últimas décadas así como también se ha evidenciado que el agua de esta presenta un origen meramente meteórico. A pesar de ello, ninguno de estos estudios hace referencia a las interacciones entre la Laguna de Hule con otros sistemas acuáticos a pesar de que se ha sugerido una posible interacción entre el agua superficial de la laguna con el agua subterránea de los acuíferos locales. Es por ello, que este estudio pretende identificar la posible conectividad hidrológica de la Laguna de Hule con el sistema subterráneo aledaño a la Depresión de Hule, mediante la caracterización física y química utilizando isótopos estables y radiogénicos, además de otras especies. Con el fin de llevar a cabo este estudio preliminar, se realizaron dos campañas de muestreo (marzo del 2024 y septiembre del 2024), divididas en dos partes: (1) muestreo de la Laguna de Hule y (2) muestreo de las nacientes y ríos aledaños a la Depresión de Hule. A partir de estos, se determinaron parámetros físicos y químicos los cuales permitieron realizar una aproximación múltiple de trazadores isotópicos (i.e., δ2H, δ18O, δ13CDIC, 222Rn) e hidroquímicos para mejorar la comprensión de la complejidad de las interacciones estacionales entre el agua subterránea y superficial de la Laguna de Hule. Con base en los resultados obtenidos durante el estudio, se determinó que existe una baja variabilidad entre de la relación E/I (cociente de la evaporación y los flujos de entrada de agua a la laguna) de la época seca y la época lluviosa, con pérdidas por evaporación relativamente bajas (2.9 ± 1.0) % y (3.2 ± 1.8) % respectivamente. Además, mediante el análisis Bayesiano de componentes finales, se determinó los aportes anuales de agua subterránea, precipitación y escorrentía los cuales fueron de (61.3 ± 8.1) %, (24.4 ± 8.4) % y (14.3 ± 5.9) % respectivamente, concluyendo que el agua de la laguna pertenece mayoritariamente a agua subterránea. Adicionalmente, en las áreas donde predominan litologías volcánicas (e.g., Laguna de Hule), se determinó que las recargas por agua subterránea se deben mayoritariamente a intensas lluvias. Por otra parte se identificaron variaciones temporales de δ13CDIC, que confirman el papel clave que presenta la amortiguación por carbonatos en la laguna, así mismo, estas variaciones indicaron que, durante la época lluviosa, existe una mayor desgasificación de CO2 de las fuentes subterráneas que durante la época seca. Este estudio, proporciona evidencia de interacciones previamente desconocidas entre agua subterránea y agua superficial en la Laguna de Hule. Adicionalmente, pretende abrir camino a futuras investigaciones hidrológicas enfocadas en la variabilidad estacional de la descarga de agua subterránea en las lagunas tipo maar presentes a lo largo del frente volcánico de Centroamérica.
Abstract. The Hule Lagoon is a volcanic lagoon located in the protected area of the Bosque Alegre National Wildlife Refuge, approximately 11 km north of the Poas Volcano. Together with the Bosque Alegre and Congo lagoons, it forms the complex known as the Hule Depression. Previous studies of this lagoon have revealed anoxic environments in a range of 8 m to 10 m depth due to iron oxidation and hydrogen sulphide production. In addition, different mixing processes have been determined over the last decades, as well as evidence that the water in the lagoon has a purely meteoric origin. However, none of these studies refer to the interactions between the Laguna de Hule and other aquatic systems, although a possible interaction between the surface water of the lagoon and the groundwater of the local aquifers has been suggested. Therefore, this study aims to identify the possible hydrological connectivity of Laguna de Hule with the underground system surrounding the Hule Depression, by means of physical and chemical characterisation using stable and radiogenic isotopes, as well as other species. In order to carry out this preliminary study, two sampling campaigns were carried out (March 2024 and September 2024), divided into two parts: (1) sampling of the Hule Lagoon and (2) sampling of the springs and rivers surrounding the Hule Depression. From these, physical and chemical parameters were determined which allowed a multiple isotopic (i.e., δ2H, δ18O, δ13CDIC, 222Rn) and hydrochemical tracer approach to improve the understanding of the complexity of the seasonal interactions between groundwater and surface water in the Laguna de Hule. Based on the results obtained during the study, it was determined that there is a low variability between the E/I ratio (ratio of evaporation and inflows to the lagoon) of the dry and rainy seasons, with relatively low evaporation losses (2.9 ± 1.0) % and (3.2 ± 1.8) % respectively. In addition, by means of Bayesian final component analysis, the annual contributions of groundwater, precipitation and runoff were determined to be (61.3 ± 8.1) %, (24.4 ± 8.4) % and (14.3 ± 5.9) % respectively, concluding that the lagoon water belongs mostly to groundwater. Additionally, in areas where volcanic lithologies predominate (e.g., Laguna de Hule), it was determined that groundwater recharge is mostly due to intense rainfall. Moreover, temporal variations of δ13CDIC were identified, confirming the key role of carbonate buffering in the lagoon, and these variations indicated that, during the rainy season, there is a greater degassing of CO2 from groundwater sources than during the dry season. This study provides evidence of previously unknown groundwater-surface water interactions in Laguna de Hule. In addition, it aims to pave the way for future hydrological investigations focusing on the seasonal variability of groundwater discharge in maar-type lagoons along the Central American volcanic front.
Abstract. The Hule Lagoon is a volcanic lagoon located in the protected area of the Bosque Alegre National Wildlife Refuge, approximately 11 km north of the Poas Volcano. Together with the Bosque Alegre and Congo lagoons, it forms the complex known as the Hule Depression. Previous studies of this lagoon have revealed anoxic environments in a range of 8 m to 10 m depth due to iron oxidation and hydrogen sulphide production. In addition, different mixing processes have been determined over the last decades, as well as evidence that the water in the lagoon has a purely meteoric origin. However, none of these studies refer to the interactions between the Laguna de Hule and other aquatic systems, although a possible interaction between the surface water of the lagoon and the groundwater of the local aquifers has been suggested. Therefore, this study aims to identify the possible hydrological connectivity of Laguna de Hule with the underground system surrounding the Hule Depression, by means of physical and chemical characterisation using stable and radiogenic isotopes, as well as other species. In order to carry out this preliminary study, two sampling campaigns were carried out (March 2024 and September 2024), divided into two parts: (1) sampling of the Hule Lagoon and (2) sampling of the springs and rivers surrounding the Hule Depression. From these, physical and chemical parameters were determined which allowed a multiple isotopic (i.e., δ2H, δ18O, δ13CDIC, 222Rn) and hydrochemical tracer approach to improve the understanding of the complexity of the seasonal interactions between groundwater and surface water in the Laguna de Hule. Based on the results obtained during the study, it was determined that there is a low variability between the E/I ratio (ratio of evaporation and inflows to the lagoon) of the dry and rainy seasons, with relatively low evaporation losses (2.9 ± 1.0) % and (3.2 ± 1.8) % respectively. In addition, by means of Bayesian final component analysis, the annual contributions of groundwater, precipitation and runoff were determined to be (61.3 ± 8.1) %, (24.4 ± 8.4) % and (14.3 ± 5.9) % respectively, concluding that the lagoon water belongs mostly to groundwater. Additionally, in areas where volcanic lithologies predominate (e.g., Laguna de Hule), it was determined that groundwater recharge is mostly due to intense rainfall. Moreover, temporal variations of δ13CDIC were identified, confirming the key role of carbonate buffering in the lagoon, and these variations indicated that, during the rainy season, there is a greater degassing of CO2 from groundwater sources than during the dry season. This study provides evidence of previously unknown groundwater-surface water interactions in Laguna de Hule. In addition, it aims to pave the way for future hydrological investigations focusing on the seasonal variability of groundwater discharge in maar-type lagoons along the Central American volcanic front.
Descripción
Montealegre Viales, E. (2024). Caracterización física y química de la laguna Hule para la estimación preliminar de su conectividad hidrológica con el sistema subterráneo aledaño a la depresión Hule. [Tesis de Licenciatura]. Universidad Nacional, Heredia, Costa Rica.
Palabras clave
LAGUNAS, REFUGIO NACIONAL DE VIDA SILVESTRE BOSQUE ALEGRE (COSTA RICA), HIDROLOGÍA, GASES, RÍO CUARTO (ALAJUELA), AGUAS SUBTERRÁNEAS, GROUNDWATER, LAGOONS, HYDROLOGY