Caracterización Hidroquímica de Cuencas Andinas con Énfasis en la Zona Semiárida de Chile
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Date
2025
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Universidad de Concepción
Abstract
Dada la importancia hidrológica de las cuencas de cabecera para los ecosistemas y las actividades humanas, comprender la dinámica hidroquímica de las cuencas de cabecera de montañas y la influencia de las características de las cuencas en la calidad del agua es esencial para diseñar estrategias de gestión eficaces. Especialmente relevante es la zona semiárida en Chile donde el abastecimiento hídrico proviene principalmente de las cuencas andinas. El objetivo principal de la presente tesis fue caracterizar la hidroquímica de cuencas andinas con énfasis en la zona semiárida de Chile. Como primer enfoque (Capitulo II) se abordó un análisis hidroquímico de largo plazo y baja frecuencia para un transecto de treinta cuencas, mediante la determinación de la relación caudal concentración (c-Q) de los ríos caracterizando los regímenes de exportación (enriquecimiento, dilución y constate) con la ley de potencia y los patrones de histéresis (sentido horario, sentido antihorario y no-histéresis). El patrón predominante para los iones mayores resultó ser dilución- antihorario y para Fe enriquecimiento-horario Además, para determinar la composición iónica del agua, se aplicó el diagrama de Stiff, y se identificó fuentes relevantes de aporte de solutos. Con estadísticos no paramétricos U de Mann-Whitney y δ de Cliff se analizó la relación entre características climáticas y de terreno con la relación c-Q. Para el segundo enfoque (Capítulo III), considerando el rol relevante de los humedales en la hidroquímica, se analizó, durante 37 años (verano), la relación entre la cobertura vegetal, la precipitación y la concentración de solutos en una cadena de doce humedales altoandinos del Santuario de la Naturaleza Estero Derecho, mediante los índices NDVI y NDMI obtenidos de los satélites Landsat-5 y Landsat-8. Se determinó correlación significativa entre ambos índices, la precipitación y parámetros de calidad del agua (CE, Cl, Mg, Na y Fe). El análisis de la cobertura vegetal de cada humedal mostró diferentes comportamientos, atribuibles a la altitud, la pendiente del terreno y los aportes hídricos adicionales de los arroyos. Finalmente, de manera integrada la investigación ha logrado resultados que ofrecen una caracterización de la dinámica hidroquímica de las cuencas andinas estudiadas y como factores naturales y antropogénicos influyen en el comportamiento de los parámetros de la calidad del agua. La relación identificada entre el comportamiento de los solutos, el índice de aridez y la cobertura vegetal permite, en un escenario de cambio climático, proyectar cambios en la hidroquímica de los ríos que sirvan de insumo para tomas de decisión en la gestión de cuencas. Considerando la amplitud del transecto (29°-35°S), la diversidad de condiciones de las diferentes cuencas, incluido el humedal de altura, esta investigación puede ser útil para estudios similares, en especial para cuencas montañas donde es habitual la escasez de datos. Se plantea proyecciones de estudios sobre la caracterización de fuentes específicas de los solutos, dinámica nival, aporte de aguas subterráneas y caracterización física y química de los sedimentos. El estudio de la cadena de humedales tuvo una aplicación directa a la comunidad ya que la información generada será considerada para actualizaciones del plan de manejo y educación ambiental del Santuario.
Understanding the hydrochemical dynamics of mountain headwater basins—and the influence of catchment attributes on water quality, is essential for designing effective water-resource management strategies, given their hydrological importance for both ecosystems and human activities. This is particularly relevant in the semi-arid zone of Chile, where water supply depends largely on Andean headwaters. The main objective of this thesis was to characterize the hydrochemistry of Andean catchments, with an emphasis on semi-arid Chile. In the first component (Chapter II), a long-term, low-frequency hydrochemical analysis was conducted for a transect of thirty basins. Concentration–discharge (c–Q) relationships were evaluated to characterize export regimes (enrichment, dilution, constancy) using power-law scaling, alongside hysteresis patterns (clockwise, anticlockwise, no hysteresis). Major ions predominantly exhibited dilution–anticlockwise behavior, whereas Fe showed enrichment–clockwise patterns. Water ionic composition was examined using Stiff diagrams, enabling identification of key solute sources. Non-parametric Mann–Whitney U tests and Cliff’s delta were applied to assess links between climatic and terrain characteristics and c–Q behavior. In the second component (Chapter III), recognizing the hydrological relevance of high-Andean wetlands, the relationship between vegetation cover, precipitation, and solute concentrations was analyzed over 37 summers for a chain of twelve wetlands within the Estero Derecho Nature Sanctuary. Vegetation indices (NDVI and NDMI) derived from Landsat-5 and Landsat-8 revealed significant correlations with precipitation and with water-quality parameters (EC, Cl, Mg, Na, Fe). Vegetation-cover dynamics differed among wetlands, influenced by altitude, terrain slope, and additional inflows from tributary streams. Overall, this research provides an integrated characterization of hydrochemical dynamics in Andean basins and demonstrates how natural and anthropogenic factors shape water-quality behavior. The identified links between solute dynamics, aridity index, and vegetation cover offer a basis for projecting hydrochemical responses under climate-change scenarios, supporting informed decision-making in catchment management. Given the geographic breadth of the transect (29°–35°S) and the heterogeneity among basins—including high-altitude wetlands—the results of this study may inform similar research, particularly in mountain regions where data scarcity is common. Future work should include the characterization of specific solute sources, snow-regime dynamics, groundwater contributions, and the physical and chemical properties of sediments. The wetland-chain analysis also had direct application for the local community, as the information generated will contribute to updating the management plan and environmental-education initiatives of the Sanctuary.
Understanding the hydrochemical dynamics of mountain headwater basins—and the influence of catchment attributes on water quality, is essential for designing effective water-resource management strategies, given their hydrological importance for both ecosystems and human activities. This is particularly relevant in the semi-arid zone of Chile, where water supply depends largely on Andean headwaters. The main objective of this thesis was to characterize the hydrochemistry of Andean catchments, with an emphasis on semi-arid Chile. In the first component (Chapter II), a long-term, low-frequency hydrochemical analysis was conducted for a transect of thirty basins. Concentration–discharge (c–Q) relationships were evaluated to characterize export regimes (enrichment, dilution, constancy) using power-law scaling, alongside hysteresis patterns (clockwise, anticlockwise, no hysteresis). Major ions predominantly exhibited dilution–anticlockwise behavior, whereas Fe showed enrichment–clockwise patterns. Water ionic composition was examined using Stiff diagrams, enabling identification of key solute sources. Non-parametric Mann–Whitney U tests and Cliff’s delta were applied to assess links between climatic and terrain characteristics and c–Q behavior. In the second component (Chapter III), recognizing the hydrological relevance of high-Andean wetlands, the relationship between vegetation cover, precipitation, and solute concentrations was analyzed over 37 summers for a chain of twelve wetlands within the Estero Derecho Nature Sanctuary. Vegetation indices (NDVI and NDMI) derived from Landsat-5 and Landsat-8 revealed significant correlations with precipitation and with water-quality parameters (EC, Cl, Mg, Na, Fe). Vegetation-cover dynamics differed among wetlands, influenced by altitude, terrain slope, and additional inflows from tributary streams. Overall, this research provides an integrated characterization of hydrochemical dynamics in Andean basins and demonstrates how natural and anthropogenic factors shape water-quality behavior. The identified links between solute dynamics, aridity index, and vegetation cover offer a basis for projecting hydrochemical responses under climate-change scenarios, supporting informed decision-making in catchment management. Given the geographic breadth of the transect (29°–35°S) and the heterogeneity among basins—including high-altitude wetlands—the results of this study may inform similar research, particularly in mountain regions where data scarcity is common. Future work should include the characterization of specific solute sources, snow-regime dynamics, groundwater contributions, and the physical and chemical properties of sediments. The wetland-chain analysis also had direct application for the local community, as the information generated will contribute to updating the management plan and environmental-education initiatives of the Sanctuary.
Description
Tesis presentada para optar al grado de Doctora en Recursos Hídricos y Energía para la Agricultura
Keywords
Cuencas hidrográficas - Chile, Abastecimiento de agua, Calentamiento global - Aspectos ambientales