Turbulence metrics at the surface of rivers, measured by Infrared Quantitative Image Velocimetry (IR-QIV)

In recent years the changing climate has resulted in an increased prevalence of extreme weather, with corresponding extreme precipitation and surface flow events. Adapting management of water and other natural resources to these conditions requires accurate and robust tools to measure water flow, and in particular the development of non-contact measurement methods.

Once such method is Infrared quantitative image velocimetry (IR-QIV), which is a large scale surface velocimetry method that uses infrared imagery to calculate the mean and instantaneous velocity at high resolution in space and time, over large spatial areas (Schweitzer & Cowen, WRR 2021). IR-QIV can operate continuously for extended periods (days, weeks, etc.) without requiring artificial illumination or particle seeding of the flow. The high resolution, continuous, measurement capabilities of IR-QIV make it particularly well suited to applications where the spatial and temporal variance of the flow must be resolved, such as fishery management, air-water heat and gas exchange, and flow-structure interaction studies.

We present metrics of turbulence, estimates of gas transfer rates, and other hydrodynamic properties calculated from velocity measurements conducted by IR-QIV at the surface of several rivers in California, and Michigan, USA. The measurements were made as part of fishery management projects, motivated by efforts to better understand and manage the interaction of migrating fish and the hydrodynamic environment. Results are validated by comparison with acoustic velocity measurements.