A Unifying Model for Turbulent Hyporheic Mass Flux Under a Wide Range of Near‐Bed Hydrodynamic Conditions.

Existing models for estimating hyporheic solute mass flux often require numerous parameters related to flow, bed, and channel characteristics, which are frequently unavailable. We performed a meta‐analysis on existing data set, enhanced with high Reynolds number cases from a validated Computational Fluid Dynamics model, to identify key parameters influencing effective diffusivity at the sediment water interface. We applied multiple linear regression to generate empirical models for predicting eddy diffusivity. To simplify this, we developed two single‐parameter models using either a roughness or permeability‐based Reynolds number. These models were validated against existing models and literature data. The model using roughness Reynolds number is easy to use and can provide an estimate of the mass transfer coefficient for solutes like dissolved oxygen, particularly in scenarios where detailed bed characteristics such as permeability might not be readily available. Plain Language Summary: Current methods for estimating solute mass transfer across the sediment‐water interface of rivers often require a lot of information about flow and riverbed characteristics. Unfortunately, this information is often not readily available. We evaluated existing data from flume experiments and the field and added new data from a verified computational model, in order to identify which factors are most important in determining how much solute moves toward the bed at the sediment‐water interface. Using statistical tools, we developed two simple models that require minimal information about the stream and streambed. One model considers sediment size, the other looks at riverbed permeability. We validated these models by comparing them to existing methods and data from other studies, and they performed well. The model based on sediment size, which also reflects the roughness of the riverbed, performs best and is the most user‐friendly because it does not require information about permeability, which is harder to estimate. This model can be further applied for dissolved oxygen transfer and provide a reliable estimate of how oxygen moves at the sediment‐water interface, particularly when specific details about the riverbed are not available. Key Points: We used a validated numerical model to expand the available data set of hyporheic mass exchange under various bed and flow conditionsWe performed reanalysis of flume/field data combined with numerical results to develop models for the hyporheic mass exchange rateWe proposed unifying single‐parameter models for the estimation of hyporheic mass transfer coefficient in open‐channel flows [ABSTRACT FROM AUTHOR]