Evolución de la salinidad en un estuario pequeño en distintas condiciones de caudal y marea.
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Date
2025
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Publisher
Universidad de Concepción
Abstract
Los estuarios pequeños se caracterizan por presentar bajos caudales de agua fresca con alta variación estacional y por pertenecer a cuencas de pequeña magnitud. La hidrodinámica de estuarios obedece principalmente a la relación que exista entre los procesos fluvio – mareales, es decir la relación entre mareas, oleaje y caudal. La importancia de estos cuerpos de agua radica en que representan entornos únicos y con hidrodinámica compleja que afecta de manera directa en la ecología del entorno ya que en ellos ocurren procesos biológicos e hidrológicos, como el intercambio de nutrientes, el transporte de sedimentos fluvio-marino, la purificación del agua y ofrecen protección frente a inundaciones. Tal es el caso del estuario de Laraquete que se forma en la confluencia de dos cauces que drenan dos cuencas costeras y no representa necesariamente el escenario más común. El presente estudio tiene como objetivo analizar el comportamiento de la intrusión salina en el estuario Laraquete, ubicado en la Región del Biobío, Chile, mediante la implementación de un modelo numérico bidimensional en el software IBER. Se recopilaron datos batimétricos, topográficos, hidrológicos y de marea, y se realizaron campañas de terreno para obtener mediciones de profundidad y velocidad en el estuario. El modelo fue calibrado y validado satisfactoriamente, y luego se definieron ocho escenarios de simulación combinando mareas de sicigia y cuadratura con caudales altos y bajos, incluyendo un escenario de crecida. Los resultados del modelo indicaron que la propagación de la marea en el estuario genera un comportamiento sinusoidal en la profundidad, en la velocidad y en la salinidad, alcanzando diferentes distancias desde la desembocadura de acuerdo el escenario de caudal propuesto considerado. Se concluye que la hidrodinámica del estuario de Laraquete está fuertemente condicionada por la interacción entre caudales y mareas. La marea predomina como forzante principal durante periodos de caudales bajos, aumentando la intrusión salina, mientras que el flujo de agua dulce es dominante en invierno, limitando significativamente la salinidad dentro del estuario. La morfología del estuario, sus pendientes y su escala reducida permiten observar con claridad estos patrones, lo que valida el uso de modelos numéricos como herramienta eficaz para la evaluación y gestión de estuarios de pequeña escala.
Small estuaries are characterized by low freshwater flows with high seasonal variation and by belonging to small-scale watersheds. The hydrodynamics of estuaries are primarily governed by the interaction between riverine and tidal processes, that is, the relationship between tides, waves, and discharge. The importance of these water bodies lies in the fact that they represent unique environments with complex hydrodynamics that directly affect the surrounding ecology, as they host biological and hydrological processes such as nutrient exchange, fluvio-marine sediment transport, water purification, and providing protection against flooding. Such is the case of the Laraquete estuary, which is formed at the confluence of two channels draining two coastal watersheds and does not necessarily represent the most common scenario. The aim of the present study is to analyze the behavior of saline intrusion in the Laraquete estuary, located in the Biobío Region, Chile, through the implementation of a two-dimensional numerical model using the IBER software. Bathymetric, topographic, hydrological, and tidal data were collected, and field campaigns were conducted to obtain depth and velocity measurements in the estuary. The model was successfully calibrated and validated, and eight simulation scenarios were then defined by combining spring and neap tides with high and low discharges, including a flood event scenario. The model results indicated that tidal propagation in the estuary generates a sinusoidal pattern in depth, velocity, and salinity, reaching different distances from the mouth of the estuary depending on the proposed flow scenario. It is concluded that the hydrodynamics of the Laraquete estuary are strongly influenced by the interaction between freshwater flow and tidal forces. Tides prevail as the main driving force during low-flow periods, increasing saline intrusion, whereas freshwater flow dominates during winter, significantly limiting salinity within the estuary. The estuary’s morphology, slopes, and small scale allow these patterns to be clearly observed, validating the use of numerical models as an effective tool for the assessment and management of small-scale estuaries.
Small estuaries are characterized by low freshwater flows with high seasonal variation and by belonging to small-scale watersheds. The hydrodynamics of estuaries are primarily governed by the interaction between riverine and tidal processes, that is, the relationship between tides, waves, and discharge. The importance of these water bodies lies in the fact that they represent unique environments with complex hydrodynamics that directly affect the surrounding ecology, as they host biological and hydrological processes such as nutrient exchange, fluvio-marine sediment transport, water purification, and providing protection against flooding. Such is the case of the Laraquete estuary, which is formed at the confluence of two channels draining two coastal watersheds and does not necessarily represent the most common scenario. The aim of the present study is to analyze the behavior of saline intrusion in the Laraquete estuary, located in the Biobío Region, Chile, through the implementation of a two-dimensional numerical model using the IBER software. Bathymetric, topographic, hydrological, and tidal data were collected, and field campaigns were conducted to obtain depth and velocity measurements in the estuary. The model was successfully calibrated and validated, and eight simulation scenarios were then defined by combining spring and neap tides with high and low discharges, including a flood event scenario. The model results indicated that tidal propagation in the estuary generates a sinusoidal pattern in depth, velocity, and salinity, reaching different distances from the mouth of the estuary depending on the proposed flow scenario. It is concluded that the hydrodynamics of the Laraquete estuary are strongly influenced by the interaction between freshwater flow and tidal forces. Tides prevail as the main driving force during low-flow periods, increasing saline intrusion, whereas freshwater flow dominates during winter, significantly limiting salinity within the estuary. The estuary’s morphology, slopes, and small scale allow these patterns to be clearly observed, validating the use of numerical models as an effective tool for the assessment and management of small-scale estuaries.
Description
Tesis presentada para optar al título de Ingeniero/a Civil.
Keywords
Estuarios, Salinidad, Caudales, Mareas