In situ measurements of Rhodamine WT dye concentration and turbidity made during a tracer experiment on the Missouri River near Columbia, MO, on May 5, 2021

This child data release includes fluorometer measurements of Rhodamine WT dye concentration and turbidity acquired during a tracer experiment performed on the Missouri River near Columbia, Missouri, on May 5, 2021. One of the primary goals of this tracer experiment was to assess the feasibility of inferring concentrations of a visible dye (Rhodamine WT) from various types of remotely sensed data in a large, highly turbid natural river channel. Previous research on remote sensing of tracer dye concentrations has focused on clear-flowing streams, but the Missouri River is much more turbid. As a result, the effect of the dye on the reflectance of the water could be obscured by the effects of suspended sediment on reflectance. 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.
The experiment involved introducing a pulse of Rhodamine WT dye into the channel at an upstream transect and then observing the dispersion of the dye along the river using various in-situ and remote sensing instruments. In-situ measurements of Rhodamine WT concentration were used to quantify the passage of the dye over the course of the experiment at several locations throughout the 13.8-km study reach. Turner C3 Submersible Fluorometers were placed at seven fixed monitoring locations at distances from 2.8 to 7.3 km downstream the dye release transect and measured the Rhodamine WT dye concentration in parts per billion (ppb). In addition, the fluorometers measured turbidity in nephelometric turbidity units (NTU). Each fluorometer was attached to a buoy and its position was established using a Trimble R2 real-time kinematic (RTK) integrated global navigation satellite system (GNSS) receiver. Six of the fluorometers were placed in the main channel and one fluorometer was placed at the downstream end of the side channel on the west side of Tadpole Island. Five of the fluorometers recorded Rhodamine WT and turbidity data every 30 seconds and two fluorometers within the footprint of UAS-based videos also acquired during the experiment recorded Rhodamine WT and turbidity data every 5 seconds to provide more frequent observations for calibrating concentration estimates derived from UAS-based images. 
Similarly, an eighth fluorometer set with a logging interval of 1 second was deployed on the boat from which field spectra were acquired during several transects back and forth across the channel  2.5 km downstream the dye release transect. Rhodamine WT measurements from this fluorometer were used to relate spectral reflectance to RWT concentration. The position of this fluorometer was also established using a Trimble R2 RTK GNSS receiver logging at 5 Hz mounted 2.47 m directly starboard of the fluorometer. The position of the third time stamp of every second was extracted from the GPS time string and paired with the data logged by the fluorometer using the time stamps from the fluorometer. 
All fluorometers used in the study were calibrated prior to deployment using a two-point (Rhodamine WT: 0 and 10 ppb; turbidity: 0 and 250 NTU) calibration procedure established by Turner. The calibration of each fluorometer was subsequently tested using a two-point test (Rhodamine WT: 1 and 30 ppb; turbidity: 100 and 400 NTU). To create calibration and test solutions for fluorescence, manufacturer-recommended standards were diluted in distilled water. If the test measurements deviated more than five percent from the test solution, the instrument was recalibrated and retested. 
All fluorometers were synchronized to allow the in-situ and remotely sensed data sets to be linked via time stamps. A custom python script was used to post-process the Rhodamine WT data. Post-processing consisted of removing the background fluorescence, despiking the data, and applying a five-point moving average. 
This data release provides both the Rhodamine WT concentration and turbidity measurements for each fluorometer, as well as locations and time stamps. The fluorometer data from throughout the experiment are compiled in two files, MissouriDyeFluorometers_insitu.csv and MissouriDyeFluorometers_boat.csv. The in-situ measurements are organized by station ID and also include columns for the easting and northing spatial coordinates (UTM Zone 15S, NAD83), the distance in meters downstream from the release transect, UTC time of the measurement, and hours post injection. The remaining columns include data for the raw Rhodamine WT concentration in ppb and raw turbidity in NTU. The fluorometer data measured on the boat are organized by transect number and also include the UTC time of the measurement, hours post injection, and easting and northing spatial coordinates. The remaining columns contain the raw Rhodamine WT concentration in ppb and raw turbidity in NTU.

Tags: columbia, concentration, dispersion, missouri, missouri-river, pallid-sturgeon, remote-sensing, rhodamine-dye, river, tracer-study, turbidity, usgs-62111e09d34e6c7e83bbb09c
Organization: Department of the Interior