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Developing remote sensing methods for tracer studies in rivers

By Columbia Environmental Research Center

By Susannah Erwin, PhD

April 15

USGS scientists inject dye into a tank containing turbid water intended to mimic conditions encountered on the Missouri River.
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USGS scientists inject dye into a tank containing turbid water intended to mimic conditions encountered on the Missouri River.

CERC scientists are collaborating with researchers from Missouri University of Science and Technology (Rolla, MO) and the USGS Geomorphology and Sediment Transport Laboratory in Golden, CO, part of the Water Mission Area’s Integrated Modeling and Prediction Division, to develop and test new remote sensing methods for mapping flow patterns in rivers. Tracer studies that make use of a harmless but highly visible fluorescent dye can provide insight on how the flow redistributes organisms and other materials via a process called dispersion [link to 2016 and 2017 tracer experiments]. Typically, these studies involve deploying instruments to measure dye concentration over time at discrete locations. However, pilot studies have demonstrated that passive optical remote sensing techniques could be used to produce image-derived maps of dye concentrations that provide much more extensive and detailed spatial information on dispersion patterns. These methods, developed by USGS scientist Dr. Carl Legleiter, could become a powerful tool for evaluating the performance of channel-reconfiguration projects – for example, Interception and Rearing Complexes (IRCs) for age-0 pallid sturgeon – by allowing scientists to better characterize processes such as mixing and retention.   

A drone operator from Missouri S&T prepares for takeoff
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A drone operator from Missouri S&T prepares for takeoff during hydrologic studies at the Columbia Environmental Research Center.

In April 2019, USGS scientists and colleagues from Missouri University of Science and Technology conducted experimental trials at CERC to evaluate how turbidity affects remote detection of dye from hyperspectral image data. Different combinations of dye and fine sediment were mixed in tanks and both hyperspectral images and more typical color photos were acquired using a pair of small unmanned aircraft systems (UAS). Scientists are currently evaluating the data, but the initial results from this study are encouraging, indicating the potential to incorporate a remote sensing approach into a dye tracer study planned for the Lower Missouri River at a later date in 2019.