Remote sensing of visible dye concentrations during a tracer experiment on a large, turbid river

Water Resources Research
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Abstract

Understanding dispersion in rivers is critical for numerous applications, such as characterizing larval drift for endangered fish species and responding to spills of hazardous materials. Injecting a visible dye into the river can yield insight on dispersion processes, but conventional field instrumentation yields limited data on variations in dye concentration over time at a few, fixed points. Remote sensing can provide more detailed, spatially distributed information on the dye's motion, but this approach has only been tested in clear-flowing streams. The purpose of this study was to assess the potential of remote sensing to facilitate tracer studies in more turbid rivers. To pursue this objective, we injected Rhodamine WT dye into the Missouri River and collected field spectra from a boat, videos from a small unoccupied aircraft system (sUAS), and orthophotos from an airplane. Applying an optimal band ratio analysis (OBRA) algorithm to the field spectra revealed strong correlations (R2 = 0.936) between a spectrally based quantity and in situ concentration measurements. OBRA also performed well for broadband RGB (red, green, blue) images extracted from the sUAS-based videos; the resulting concentration maps were used to produce animations that captured movement of the dye pulse. Spectral mixture analysis of repeat orthophoto coverage yielded relative concentration estimates that provided a synoptic perspective on dispersion of the dye throughout the entire 13.8 km reach over the full 2.5-hr duration of the experiment. The results of this study demonstrate the potential to remotely sense tracer dye concentrations in large, highly turbid rivers.

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Publication type Article
Publication Subtype Journal Article
Title Remote sensing of visible dye concentrations during a tracer experiment on a large, turbid river
Series title Water Resources Research
DOI 10.1029/2021WR031396
Volume 58
Issue 4
Year Published 2022
Language English
Publisher American Geophysical Union
Contributing office(s) WMA - Integrated Modeling and Prediction Division
Description e2021WR031396, 23 p.
Country United States
State Missouri
City Columbia
Other Geospatial Missouri River, Searcy's Bend
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