Numerical evaluation of photosensitive tracers as a strategy for separating surface and subsurface transient storage in streams

•Numerically evaluated photosensitive tracer as a strategy to separate surface and hyporheic transient storage contributions•Jointly fitting day and night tracer data using two-storage zone model delineated hyporheic and surface transient storage•Single storage model or day-only tracer data led to biases in the parameter estimates, yet good model-data fit•Good model fit to tracer test data does not guarantee accurate estimates of stream function