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Assessment of a conservative mixing model for the evaluation of constituent behavior below river confluences, Elqui River Basin, Chile
Author(s) -
Rossi Catalina,
Oyarzún Jorge,
Pastén Pablo,
Runkel Robert L.,
Núñez Jorge,
Duhalde Denisse,
Maturana Hugo,
Rojas Eduardo,
Arumí José L.,
Castillo Daniela,
Oyarzún Ricardo
Publication year - 2021
Publication title -
river research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.679
H-Index - 94
eISSN - 1535-1467
pISSN - 1535-1459
DOI - 10.1002/rra.3823
Subject(s) - hydrology (agriculture) , drainage basin , mixing (physics) , structural basin , environmental science , settling , downstream (manufacturing) , upstream (networking) , geology , computer science , geotechnical engineering , geography , environmental engineering , geomorphology , computer network , operations management , physics , cartography , quantum mechanics , economics
Fate and transport modeling of water‐borne contaminants is a data demanding and costly endeavor, requiring considerable expertise. As such, it becomes important to know when a complex modeling approach is required, and when a simpler approach is adequate. This is the main objective herein, where a conservative mixing model is used to characterize the transport of As, Cu, Fe, and SO 4 . The study area is divided into three sectors, corresponding to the upstream, middle, and downstream portions of the Elqui River Basin, Chile. In Sector 1, acidic conditions result in the conservative transport of constituents that are sourced from acid rock drainage. In Sector 2, pH increases and transport is influenced by pH‐dependent reactions and the subsequent settling of the particulate phase. In Sector 3, there are no additional constituent inputs, and the constituents are conservatively transported downstream. Conservative transport within Sector 3 is confirmed through the development of a regression model that provides monthly estimates of SO 4 load. Whereas SO 4 and Cu concentrations are adequately approximated by the conservative mixing model, estimates of As and Fe concentrations exhibit larger errors, due to the more reactive behavior of these constituents. The fact that the simple, conservative mixing model describes SO 4 transport is a valuable result, as this constituent is known to be one of the primary indicators of mining‐related contamination in rivers. The approach could also be a useful starting point for further evaluations of the effects of climate change and hydrological variability on the water quality of rivers.