A new in situ technique is introduced and tested for the field tracer study in meandering rivers. Real-time position data from a global positioning system were integrated with in situ fluorometer data, thereby providing a 2D spatial distribution of the tracer concentration. The method was used in an intensive tracer field survey over an 83 km reach of the North Saskatchewan River downstream of the capital region wastewater treatment plant. Hydrodynamics data were also collected simultaneously by measuring streamwise water velocity and depth using an acoustic Doppler current profiler. The full mixing length for this surface bank outfall at the observed low flow condition was inferred to be 130 km. The employed technique effectively improved the understanding of mixing patterns in complex flows by providing tracer and hydrodynamic data with high spatial and temporal resolution.