A boat equipped with a differential Global Positioning System (GPS) receiver (Hemisphere Crescent A100 Smart Antenna) and a Turner Designs C3 submersible fluorometer was used to survey the spatial distribution of the Rhodamine WT dye in the Chicago Sanitary and Ship Canal (CSSC) throughout the study area. The fluorometer was installed in a fixed, downlooking orientation approximately 1 foot below the water surface. Fluorometer readings were taken at a frequency of 1 per second. Data were acquired on a personal computer running the Turner Designs C-FINS software extension for ArcGIS 10. This data acquisition software allows the C3 data to be georeferenced and plotted in real time as color-coded concentrations on a user-supplied base map. The data were logged in the CFINS program and stored as shapefiles, and raw (not georeferenced) data were stored internally on the boat-mounted C3 and downloaded at the end of each shift (every 12 hours). Survey techniques were restricted to streamwise transects along the bank of the CSSC nearest the Des Plaines River in both the upstream and downstream direction. The boat survey crew followed the wall of the canal as closely as possible, including data collection in barge slips. Mooring of barges and active barge traffic restricted surveys in some locations and led to some contamination of fluorometer data by increasing local turbidity concentrations near the active vessels. The C3 turbidity sensor was not calibrated and therefore reported only relative changes in background turbidity and not absolute turbidity values (in relative Nephelometric turbidity units (NTU)). Several vertical profiles were also made in target areas to ensure dye was not being transported near the bed without any surface detection.