This child data release includes field spectra and in situ measurements of turbidity and Rhodamine WT dye concentration acquired during an experiment performed at the USGS Columbia Environmental Research Center, near Columbia, Missouri, on April 2, 2019. The purpose of the experiment was to assess the feasibility of inferring concentrations of a visible dye (Rhodamine WT) tracer from various types of remotely sensed data in water with varying levels of turbidity. Whereas previous research on remote sensing of tracer dye concentrations has focused on clear-flowing streams, the Missouri River is much more turbid and the reflectance signal associated with the sediment-laden water could obscure that related to the presence and amount of dye. This experiment thus provided an initial test of the potential to map dye concentrations from remotely sensed data in more turbid rivers like the Missouri, where tracer studies involving the release of a visible dye can provide insight regarding the dispersal of endangered sturgeon larvae. The experiment involved manipulating the turbidity and Rhodamine WT dye concentration in two water tanks and using field spectra to quantify the reflectance characteristics of the water as the turbidity and dye concentration varied over the course of the experiment. The field spectra were recorded from above the water surface using an ASD HandHeld2 Pro spectroradiometer in reflectance mode, with periodic measurements from a Spectralon panel serving as the white reference. Each set of field spectra consisted of a total of 40 measurements from a given tank, made every 15 seconds; the turbidity and dye concentration was assumed to be fairly constant during this 10-minute time period. The individual spectra were subjected to a third-order Savitzky-Golay smoothing filter applied twice over a 15 nm window and then subset to the wavelength range from 400-900 nm.
The field spectra from throughout the experiment are compiled in a single file, TankSpectra.csv, and organized by the nominal levels of turbidity and dye concentration and field spectra set number. The file also includes columns for the actual measured turbidity and dye concentration, averaged over the 10-minute time period during which each set of spectra was recorded. The reflectance at each wavelength from 400-900 nm is given in a separate column of the file.