Potential accumulation of contaminated sediments in a reservoir of a high‐Andean watershed: Morphodynamic connections with geochemical processes

Abstract

Rapid changes due to anthropic interventions in high-altitude environments, such as the Altiplano region in South America, require new approaches to understand the connections between physical and geochemical processes. Alterations of the water quality linked to the river morphology can affect the ecosystems and human development in the long term. The future construction of a reservoir in the Lluta River, located in northern Chile, will change the spatial distribution of arsenic-rich sediments, which can have significant effects on the lower parts of the watershed. In this investigation, we develop a coupled numerical model to predict and evaluate the interactions between morphodynamic changes in the Lluta reservoir, and conditions that can potentially desorb arsenic from the sediments. Assuming that contaminants are mobilized under anaerobic conditions, we calculate the oxygen concentration within the sediments to study the interactions of the delta progradation with the potential arsenic release. This work provides a framework for future studies aimed to analyze the complex connections between morphodynamics and water quality, when contaminant-rich sediments accumulate in a reservoir. The tool can also help to design effective risk management and remediation strategies in these extreme environments.

Field and Numerical Investigation of Transport Mechanisms in a Surface Storage Zone

“…In recent years, we have investigated in detail the effects of legacy mining in the high-altitude environment of the Lluta River in northern Chile, focusing on the coupling of physical and biogeochemical processes in the system (Abarca et al, 2017;Arce et al, 2017;Contreras et al, 2015;Guerra, Gonzalez, et al, 2016;Guerra, Simonson, et al, 2016;Leiva et al, 2014). Acid drainage in this watershed has increased the concentration of elements and compounds such as arsenic, aluminum, iron, chlorides, and sulfates in the river.…”

Response of suspended sediment particle size distributions to changes in water chemistry at an Andean mountain stream confluence receiving arsenic rich acid drainage

“…Indeed, a better understanding of the relationship between PSDs and water quality is needed to understand the dynamics of contaminated sediments in rivers as well as in reservoirs and to optimize water infrastructure during mine closure operations. Contreras et al () coupled physical and geochemical processes to model the fate of arsenic in an Andean reservoir. They revealed an explicit connection between morphodynamics and the deposition of fine arsenic‐rich particles by modeling the progression of the coarse sediment mixture and assuming that all fine sediments accumulated over the bottomset bed of the delta.…”

Advanced numerical models for the propagation of floods with high-sediment concentrations in mountain rivers

“…The MUSCL scheme is used to perform the extrapolation with second order accuracy in space. The model has been validated for many cases including supercritical flows and wave propagation on dry surfaces, comparing also the results with analytical solutions and experiments that include sharp density gradients [5].…”

“…The resolution of the simulations in time and space shows the evolution of the flow in the city, and the regions where the sediment concentration produces significant changes on the velocity and flow depth. We have also performed a complete analysis on the effects of hyperconcentration on the hydrograph, velocity of the wave front, evaluating also the effects of high sediment concentrations and geomorphic drivers on the propagation of floods in mountain streams [5]. Simulations with the coupled hydrological and hydrodynamic models have high computational costs, especially if many scenarios need to be evaluated.…”