Low flow regime measurements with an automatic pulse tracer velocimeter (APTV) in heterogeneous aquatic environments

• APTV is a multi-functional sensor.
• APTV can capture the features of two dimensional flows in low flow regime well.
• APTV can fit in many types of aquatic environments for flow measurements.

Cost-effective velocity measurements at lab and field scales are required for understanding and modeling the flow characteristics in aquatic environments such as constructed wetlands, coastal marshes, lakes and reservoirs. This paper presents a new measurement device—the automatic pulse tracer velocimeter (APTV) that is designed to measure water velocities for low flow regimes (0.2–5.0 cm s−1) in heterogeneous aquatic environments using NaCl pulse tracer measurements. Hydraulic data collected in a laboratory-scale flume and field-scale constructed wetland were analyzed to determine velocity, directional flow and dispersion coefficients measured by using a cross-type and arc-type APTV. Acoustic Doppler velocimeters (ADVs) were used to collect calibration measurements in a hydraulic flume to gain fundamental understanding in support of field experiments. To test the effects of vegetation, four scenarios of laboratory-scale tests having both submerged and emergent artificial vegetation were conducted in a flume including; (1) no artificial vegetation (NAV), (2) submerged artificial vegetation (SAV) (3) emergent artificial vegetation (EAV), and (4) mix artificial vegetation (MAV). Directional flow detection and simulated storm event flow tests were conducted using an arc-type APTV data in the flume to gain perspectives of APTV performance in variable flow conditions. Cross-type APTV pulse data were eventually analyzed to determine dispersion coefficients based on the tracer curves. Finally APTVs were tested alongside an ADV for a three-day duration in a constructed wetland nearby the Everglades, Florida. Operating advantages of the APTV compared to other similar sensors were summarized in the end to enhance the application potential. Results indicate that APTVs are ideal device for affordable measurements of velocities in a 0.2–4.5 cm s−1 range with the prediction of both velocity field, direction and dispersion coefficients, and capable of autonomous deployment and control in a sensor network.