Conducting hydraulic tracer studies of constructed wetlands: a practical guide

This paper reviews and summarises the theory and techniques used when conducting hydraulic tracer tests in treatment wetlands, with particular attention paid to the practical issues to be considered during the planning and implementation phases. Typically, a single-shot impulse of tracer is introduced at the inlet and the concentration tracked at the outlet or other internal point in order to uncover information about the hydraulic characteristics of the wetland. The following aspects are discussed: the range of commonly used tracer substances, the mass of tracer to be added, and planning of the sampling regime. A range of graphical and statistical tools are described for interpreting the data from a tracer study, with example data from an impulse tracer study used to demonstrate the required computational procedures. It is recommended that a standardised approach be adopted for presenting tracer study data in order to allow the direct comparison of data from different wetland systems.