Dye Tracing & Drogue Tracking
Tracking and tracing various tidal & river flows, utilising a coloured dye or floatation drogue, provides a variety of information on the current characteristics for any environmental study.
Dye tracers are often used to determine the dispersal characteristics of natural waters receiving effluent discharges or to investigate leakage between rivers or watercourses.
Dye tracing can be either qualitative; measuring the presence of a particular flow and its rapidity, or quantitative when the amount of the traced dye is measured by specific instrumentation.
Dye is released and tracked for periods of up to twelve hours, although this is dependent on the water clarity and dispersive properties.
Dye tracing applications include pollution studies, natural flow analysis (rivers, estuaries, coastal, offshore, etc.) and outfall discharge mapping.
Dye tracing studies can also provide useful information for modelling surface and groundwater systems in addition to tracing contaminants. Fluorescent dyes, particularly those which are non-toxic, are added to water systems to provide water discharge and velocity data.
Sensitive instrumentation, such as fluorometers, allows dye concentrations measurements to be made resulting in data sets that would not be possible using less sensitive methods.
Common fluorescent dyes include Rhodamine, Fluorescein and PTSA, but other custom dyes can have unique properties that are beneficial to a specific environmental study.
ALHS’ experience in dye tracing applications includes;
Analysis of storm water and sewer drainage.
Analysis of water flows including groundwater filtration, water flows, coastal currents, lakes and rivers.
Pipeline / outfall route tracing and leak detection.
During coastal dispersion studies, the concentration levels within dye plumes can be recorded to ascertain dilution rates. The fluorometer is mobilised onto a survey vessel and set-up below the water line.
Generally this is via a moon pool configuration which offers a shaded area and assisted in eliminating unwanted sunlight from skewing any readings. Additionally, the sensor is fitted with a shade to ensure only the concentration of the dye in the water being sampled is measured.
Positioning is achieved by RTK GPS and is integrated with the fluorometer and sampling software, where data can be viewed in real time to allow analysis of the spread of the dye patch.
In addition, following release and once a dye patch had begun to spread a drogue is placed at the extents of the major axis of the expanding patch. The drogues are colour coded, i.e. RED upstream and BLUE downstream, and tracked to indicate the extents of the dye plume.
Information on the drogue positions, generally recorded via GPS loggers, can be coupled with the dye concentration levels to provide and overall data sets of the characteristics of the site.